1. Introduction

In a period marked by rapid advancements in technology, social media has emerged as a potent tool for communication, transcending geographical boundaries. Consequently, the proliferation of social media platforms has led to the rise of numerous influencers across various domains [1], [2] emphasized that influencers exert considerable influence over the purchasing decisions of their followers, underscoring the need for a comprehensive examination of various influencing factors. While this influence can yield positive outcomes, such as increased sales for companies when products are endorsed by influencers, it also carries the risk of damaging brand reputation if influencers share negative experiences with associated products or services.

The Vietnamese cosmetics market is experiencing rapid growth and intense competition, particularly in the realm of online purchases. According to Statista (2020) [3], the Vietnamese cosmetics industry is valued at $2.35 billion, with skincare products generating the highest revenue at 8.3 trillion VND. Moreover, there is a noticeable uptick in online cosmetics purchases from retailers, with website visits to cosmetics retailers increasing by 10.63% from Q2/2023 to Q3/2023 [4]. Given these market dynamics, there is an urgent need to enhance communication strategies to attract customers and maintain firms' competitive edge. Furthermore, leveraging digital influencers has proven successful for cosmetics suppliers. A report by Rodrigue, E [5] indicates that for every $1 spent on digital influencers for reviewing, public relations, or advertising cosmetics products, brands achieve an average profit of $6.5, demonstrating the effectiveness of Return On Investment (ROI) from Influencer Marketing. Consequently, the effectiveness of digital influencers in promoting cosmetics through social networks is gaining traction in Vietnam. 

Recognizing the pivotal role of influencers, companies and marketing agencies have strategically elevated influencer marketing, positioning it as a distinct branch of social media marketing [6]. This strategic shift aims to harness influencers for product promotion, service endorsements, and brand awareness on social media platforms. Moreover, Gen Z is poised to become the most significant consumer demographic, surpassing Millennials in the future. In 2020, 30% of the global population belongs to this generation [7]. With a growing interest in cosmetics among Gen Z and the influence of e-commerce platforms on their consumption habits, the relationship between Generation Z, TikTok, influencer marketing, and consumer behavior will also be explored.

2. Literature Review

2.1. Review of related definition

2.1.1. Digital Influencer

Numerous researchers have offered various definitions of digital influencers, reflecting the evolving landscape of social media. Morris, N. [8] posited that digital influence entails the ability to shape perceptions and behaviors within online social communities. Consequently, digital influencers, leveraging their significant sway on social networks, garner not only trust and engagement from their followers but also bolster the online reputation of brands or products among their audience. Through social media channels, these influencers have both a direct impact on customers’ attitudes and an indirect influence on their purchase intentions through their mindsets by offering recommendations and endorsements for various products and services. Duffy, B. [9] characterizes digital influencers as brand advocates who promote products or services to their followers, often receiving compensation in the form of free products, exposure, or nominal monetary rewards. Furthermore, Rocamora, A. [10] suggests that influencers aim to expand their influence by encouraging their audience to choose promoted products voluntarily. Enke, N. and Borchers,  N. [11] assert that digital influencers serve as intermediaries who leverage their extensive social networks to sway organizational stakeholders through their interactions, personal image, and content on social media platforms. Thus, digital influencers play a pivotal role in disseminating a company's media message, enhancing brand appeal, and promoting products to consumers through various technological platforms such as TikTok, Facebook, or Instagram.

2.1.2. The implementation of influencers on TikTok

TikTok has emerged as the fastest-growing social network in the aftermath of the pandemic. Evidenced by its status as the most globally downloaded application in both 2020 and 2021, with 1506 million and 1048 million downloads respectively, surpassing the download count of Instagram during the same period [12]. The platform's utilization of short informal videos, imbued with humor to engage followers, and its focus on a predominantly youthful audience, suggests that the peripheral route of persuasion, leveraging affective cues, may prove particularly efficacious on TikTok. With a substantial user base and an average daily usage time of nearly one hour per user [13] TikTok presents an unparalleled opportunity for capitalizing on a vast potential audience through influencer marketing. Distinguished by its playful nature and emphasis on entertainment, TikTok content diverges from the more information-oriented focus of platforms like Twitter and Facebook [14], [15].This affords TikTokers the ability to present products and services in a captivating and enjoyable manner. In contemporary times, Generation Z is not easily swayed by brand-generated content, a departure from the preferences of preceding generations. They prefer to seek input from others when making purchasing decisions rather than relying on brand communications. According to Daugherty, T. [16], 92% of consumers indicate that User Generated Content (UGC), content created by users, is the most trusted form of advertising. Consequently, the collaboration of brands with influential individuals on the TikTok social platform emerges as an effective Influencer Marketing strategy.

As consumers increasingly turn to social media as a source of information to inform their decision-making process, the influencer phenomenon has burgeoned. Influencers, prominent figures within social networks, are perceived as role models by other users who trust their opinions and follow their recommendations, particularly in areas such as fashion, lifestyle, photography, and travel [17]. Influencers are now regarded as essential conduits for communication with consumers. The research underscores that influencers cultivate closer and more credible relationships with their followers compared to celebrities, underscoring their pivotal role in influencer marketing as a mechanism for consumer persuasion [18].

2.1.3. Generation Z 

Generation Z (Gen Z), comprising individuals born between 1996 and 2012 as defined by Schwieger, D. [19], constitutes a significant demographic segment, representing 33% of the global population and 21% of Vietnam's populace [20]. Identified as "the very first digital natives" [21]. Generation Z has been deeply immersed in the rapid evolution of Internet technologies, making digital tools an integral aspect of their daily routines. The advent of the 21st century witnessed a technological explosion, with the Internet proliferating worldwide, highlighting the immense and escalating allure of online shopping among Generation Z consumers. Arilaha, M. et al [22] corroborate the dominance of Generation Z in the online shopping landscape.

Wood, S. et al. [23] and Priporas, C. et al. [24] have highlighted that Generation Z consumers demonstrate preferences characterized by a penchant for new technologies, simplicity, security, and escapism, coupled with high expectations and a pronounced inclination towards experiential consumption. Additionally, they have shown a favorable response to advertisements portraying authentic depictions of real-life situations [25]. Despite their extensive engagement with social media and online content, Generation Z consumers exhibit limited tolerance for traditional advertising methods, indicating the growing significance of social media platforms and online influencers as effective marketing channels, thereby eclipsing conventional approaches that have experienced diminishing efficacy [26].

2.1.4. Purchase Intentions  

Purchase intentions are a crucial aspect of the consumer buying process. Consumer purchase decisions are intricate, and purchase intentions are a component of this multifaceted process [27]. Purchase intentions are defined as a form of decision-making aimed at understanding why a buyer intends to purchase a particular brand [28]. Meanwhile, Spears N et al [29] characterize purchase intentions as "an individual's conscious plan to make an effort to purchase a brand." Ghosh, A. [30] states that understanding consumers' purchase intentions is of great importance, as it relates to consumers’ behavior, perception, and attitude, and can therefore be used to predict the buying process. Purchase intentions for a particular product are shaped by various factors, encompassing the product's price, customer knowledge, product packaging, perception of consumers, quality, celebrity endorsements, and occasionally, familial relationships [31]. Additionally, consumers are influenced by internal and external motivations during the purchasing process [32]. Furthermore, purchase intentions can be assessed through shopping expectations and consumer evaluations of the product or service [33]. Pavlou, P. [34] affirmed that when a customer intends to use online transactions to purchase within the context of social networks, it is referred to as online purchase intentions.

2.1.5. Overview of the Beauty Market in Vietnam 

The cosmetics and beauty industry in Vietnam has experienced rapid expansion, emerging as one of the most swiftly growing sectors in Southeast Asia, with a market value surpassing US$528.9 million in 2023 [4]. Projections indicate that revenue in Vietnam's Beauty & Personal Care market is poised to ascend to US$619.50 million by 2028, with an anticipated annual growth rate of 3,20% (CAGR 2024-2028). The array of beauty care products under examination in this research encompasses various personal care items, spanning oral care, skincare, sun protection, hair care, makeup, body care, and fragrances. The proliferation of digital technology has instigated notable shifts in Vietnamese lifestyles, elevating the significance of maintaining enduring youthfulness and robust health. Consequently, digital advancements have influenced consumer expectations regarding beauty products and have consequently impacted their quality of life. Concurrently, the proliferation of E-commerce and M-commerce platforms has reshaped the shopping habits of Vietnamese consumers. Online sales are forecasted to constitute 20.2% of the total revenue in the Beauty & Personal Care market by 2024 [35]. Notably, there is a burgeoning inclination among Vietnamese consumers towards embracing natural and organic beauty products, thereby propelling the expansion of the Beauty & Personal Care market in Vietnam. 

2.2. Review of relevant theoretical model

According to Ohanian, R. (1990), the source credibility theory suggests that individuals are more likely to be persuaded by trustworthy individuals. This theory encompasses three key components: Expertise, Trustworthiness, and Attractiveness.

The reason for choosing the Source credibility model as the theoretical framework 

The model could be utilised to explore the influence of influencers on customers' purchasing intentions regarding cosmetics products in Vietnam. Consumers who engage with technology platforms tend to prefer products recommended by influencers across a wide range of price points, from budget-friendly to luxury cosmetics. Based on influencers' reputations, their followers trust their recommendations and are inclined to choose products endorsed by these credible individuals. The source credibility model has been extensively employed to assess the impact of celebrities on purchasing intent, and it has previously been validated to gauge the effect of celebrities on purchase intentions. Given the aim of this study to investigate the characteristics of influencers, the source credibility model is appropriately proposed as the research framework.

2.3. Model development and conceptual model

The development of the research model involves the application of three constructs from the Source Credibility Model: expertise, trustworthiness, and attractiveness. The study conducted by Syed, A. [40] examined the  Effectiveness of Social Media Influencers in Brand Purchase intentions in India and incorporated two supplementary variables, Product Fit, and Similarity, into the original model for examination. Results indicated that both Product Fit and Similarity exerted a significant impact on purchase intentions within the Indian context. Therefore, the author aims to assess additional characteristics of digital influencers, the alignment between the product and the influencers, as well as the perceived quality by customers, the roles of similarity and product fit will be incorporated into this model. Consequently, the author integrates these two factors into the original model to gain deeper insights into their influence on purchase intentions in Vietnam. 

2.3.1. Trustworthiness 

Trustworthiness is defined as the perceived willingness of an influencer to provide accurate and reliable information to consumers or followers, offering genuine and truthful insights regarding a product [37]. It represents the credibility, integrity, belief, and faith of the source in elucidating the fundamental implications of shifts in customer sentiment [41]. When consumers perceive a source as trustworthy, they are inclined to rely on the endorsed products, thereby enhancing the purchase intentions for cosmetics items [42]. The degree of trust and allegiance established between consumers and their influencers has been observed to have a constructive impact on the longevity of their relationships, as well as on sales and brand performance. In the absence of trust, various attributes held by the endorser fail to effectively alter customer perceptions [43]. Consequently, a strong belief in the source can significantly shape consumers' perception of value and subsequently impact their purchasing decisions [44].

2.3.2. Expertise 

Expertise is defined as the level of knowledge, perception, and skills acquired by influencers [39]. Previous research has indicated that the recipient's purchasing decision and perceived reliability may be influenced by the source's expertise in the product domain. When consumers recognize influencers as possessing high expertise, they are more likely to trust in the quality of endorsed products [45], [46] argue that an endorser's expertise enhances the accuracy of product claims, thereby bolstering the persuasive power of advertisements. Ultimately, influencers' perceived expertise should cultivate trust and foster positive relationships between the influencer, the endorsed product, and the audience.

2.3.3. Attractiveness 

Similarly, attractiveness also directly influences the effectiveness of a company's message on social platforms [47]. Wei, P. and Lu, H. [48] found that attractiveness serves as a means to enhance consumers' perception through physical appearance, similarity, and likability. Key variables of source attractiveness include similarity, familiarity, and sympathy [49]. Furthermore, the construct of source credibility and its factors for evaluating and selecting celebrities are crucial, depending on attitudes and behavioral intentions. The source credibility model is subjective, and differences in preferences demonstrate varying degrees of agreement among individuals [5]. Ohanian, R. [37] identified three components of the source credibility model - attractiveness, expertise, and trustworthiness - after extensive testing and review. These factors appear to serve as criteria for selecting influencers for brands or products.

2.3.4. Product Fit

Product fit refers to the effectiveness of influencer reviews when there is a connection between the characteristics of influencers and the products they review [51]. Therefore, ensuring consistency between the influencer's image and the properties of the product being reviewed can enhance the persuasiveness of the review. As noted by Kamins, M. [52], product fit entails the alignment between the reviewer and the reviewed product. When reviewers have a strong connection and alignment with the products they review, it positively influences consumer purchase intentions [53]. Research by Simonin, B. and Ruth, J. (1998) revealed a positive relationship between product fit and attitudes toward purchase intentions. In the context of endorsement theory, product fit, particularly in terms of expertise, has a greater impact on attitudes toward the brand and purchase intentions compared to physical attractiveness [36]. The alignment between the product and endorser significantly affects purchase intentions, indicating that the suitability of the celebrity endorser can enhance product sales. 

2.3.5. Similarity 

Martensen et al. define similarity as the degree of resemblance between a sender and a receiver, indicating that individuals who perceive similarities with others tend to experience greater interpersonal attraction, trust, and understanding compared to those who perceive dissimilarities [54], [55]. The author further elucidates that in offline contexts, if the receiver perceives the sender as similar to themselves, they are more susceptible to persuasion by the sender. It is inferred that the more similarity individuals perceive with the influencer, the higher the level of trust they have in them. Consumers who perceive shared interests, values, or characteristics with influencers are more inclined to adopt their beliefs, attitudes, and behaviors [56], [57]. Researchers Djafarova and Rushworth (2017), suggest that influencers serve as distant yet relatable friends to their followers, as they are perceived as more approachable and relatable. This perception is primarily fostered by influencers' engagement with their followers in their posts, which creates a sense of closeness [58].

3. Research Purposes 

3.1. Research Methodology

Mixed method research utilizes both approaches iteratively or concurrently to yield a research outcome that is more robust than either method alone, facilitating the exploration of more intricate aspects and relationships within the human and social domain [59]. This study employs a mixed-methods approach to investigate the impact of influencer marketing on Gen Z purchase intentions in the cosmetics industry on TikTok. The mixed-methods design incorporates both quantitative and qualitative techniques to provide a comprehensive understanding of the research phenomenon. 

3.2. Quantitative Phase

3.2.1. Survey Sampling

This quantitative research study employed an eleven-item online survey conducted via Google Forms from March 17 to April 5, 2023. The survey targeted primarily individuals aged between 12 and 28, including university students in the Hanoi area, as well as final-year high school students from both public and international schools. The sample consisted of 154 university students (65.81%), 48 high school students (20.51%), and 32 employed individuals (13.68%). The survey comprised three distinct sections. The survey consisted of three distinct sections. The initial section consisted of three inquiries designed to collect demographic data. Subsequently, the second section was dedicated to examining the perceptions of Vietnamese youth concerning advertising content on TikTok. Lastly, the third section sought to investigate the influence of TikTok influencers within the beauty and cosmetics sector on the online purchasing behavior of young individuals. 

3.2.2. Quantitative Results

Demographic Analysis 

More than half of the survey participants were female, taking up 54.7%. The number of people who defined themselves as Male and LGBTQ+ is 40.2% and 5.1%, respectively. 

The distribution of survey participants across age groups is uneven, with a predominant representation of individuals aged 18 to 24, accounting for 65.8% of the sample. This is followed by the 15 to 18 age group, comprising 20,5% of respondents. Only a small percentage, 12.8%, of survey participants were respondents from 24 to 35 years old, while those over the age of 35 accounted for 0.9% of the sample. The survey predominantly attracted individuals from the Gen Z demographic, particularly those in their early twenties who are transitioning into the workforce. 

Financial Habits and Expenditure

A majority of the respondents indicated that their income falls within the range of 5 to 7 million. Approximately 20.5% reported an income range of 7 to 10 million, while 9.4% stated their income to be between 3 to 5 million. Less than 10% of the respondents reported a double-digit income or higher.

In general, 47.4% of respondents spend between 1 and 3 million VND per month on shopping, 44.4% of respondents spend between 3 and 5 million, and about 7.9% of respondents more than 5 million and less than 1 million per month on shopping. 

Respondents behaviour with Influencer Marketing on TikTok

Approximately 59.4% of the respondents allocate 2 to 3 hours per day to watch TikTok, while 24.8% dedicate 3 to 4 hours daily for the same activity. Only 8.5% reported spending 1 to 2 hours per day on TikTok, and a further 7.3% spend more than 4 hours per day on the platform.

When asked how frequently they view TikTok videos with promotional content, 51.7% of participants surveyed said that about 2-4 times per day, 44% seen promotional content more than 5 times while 4.3% saw it once per day.

The findings reveal that over three-quarters of respondents have made purchases based on influencer reviews. Among them, 50.4% indicated frequent purchases, while 26.5% stated they had made occasional purchases (less than 3 times). Conversely, 23.1% of respondents stated that they have never made a purchase based on a digital influencer's recommendation.

Regarding purchasing behaviour, a substantial 80.3% of survey participants reported viewing a TikTok review clip prior to making a purchase. This data underscores the considerable impact wielded by TikTok influencers on the purchasing decisions of young individuals

Influencer Factors

According to the survey results, it is evident that factors like the trustworthiness of the content (173 votes), the similarity between digital influencers and viewers (152 votes), and the product fit (135 votes) exert the most significant influence on customers' purchase intentions. Additionally, factors such as the attractiveness of the influencer (119 votes) and the expertise of the influencer (111 votes) were also found to significantly impact purchase intentions.

76.9% of survey respondents believe influencers on TikTok have a greater influence on their online shopping behaviour than influencers on other platforms. 

3.3. Qualitative Phase

3.3.1. Sampling

After examining the outcomes of the survey, the selection of participants for the in-depth interview section comprised university and high school students in Hanoi. The selected interviewees were based on criteria such as frequent engagement in shopping guided by digital influencers' reviews and the capacity for critical thinking, as demonstrated in responses to open-ended questions, regarding purchase intentions within the cosmetics sector on TikTok. It is imperative to engage the survey respondents in comprehensive discussions to gain a deeper understanding of the survey findings. A total of 5 respondents were selected to partake in in-depth interviews, including 3 university students - one from the Academy of Journalism and Communication, one from the School of National Economics, and one from British University Vietnam - as well as 2 high school students, one from Hanoi Academy Bilingual International School and the other from Nguyen Thi Minh Khai Public School.

3.3.2. Procedure

Interviews were conducted online, with respondents initially contacted using the contact information provided in the survey. Prior to the interview, participants were required to complete an informed consent form, confirming their voluntary agreement to take part in the study. The online interviews were conducted via video call on Facebook Messenger, allowing participants the option to conceal or reveal their faces at their discretion. Each interview session lasted between 30 minutes to 1 hour and 10 minutes. The responses provided by the interviewees were recorded and transcribed to facilitate comprehensive analysis.

3.3.3. Qualitative Results

Attractiveness 

The majority of the interviewees agreed that appearance is the primary factor that grabs viewers' attention and prompts them to watch a video. The interviewee indicates: 

“ The initial factor that catches my attention and prompts me to watch a video is the appearance.”[22, M]

“I like seeking out the product through the recommendation of influencers with beautiful faces, and smooth skin.”[21, F]

Upon observing attractive influencers, individuals are inclined to seek information regarding the products they endorse, aspiring to have their aesthetic appeal by utilizing the same products.

“ I am drawn to influencers who embody ideals of beauty and aesthetic appeal. When influencers showcase attractive features, flawless skin, and stylish presentation, it captivates my attention. This aesthetic appeal creates a sense of aspiration and desire among me, as they associate beauty with product efficacy and desirability." [21, M]

Nevertheless, certain individuals contend that physical appearance does not singularly dictate their purchase intentions. She said: 

"Indeed, appearance matters significantly, but it's not everything. When considering buying a skincare product, I look at various other factors besides just appearance." [18, M]

Trustworthiness

Disclosing the fact that a product is being advertised, along with transparency regarding the compensation received for a review, enhances consumers' perceptions of influencers' trustworthiness.

" In general, I'm not automatically put off by paid partnerships, but I do feel more trusting towards influencers when they disclose these partnerships. If the influencer genuinely enjoys the product and provides reasons why, I might be persuaded to consider it. Transparency plays a crucial role for me." [21, F]

Customers may exhibit skepticism regarding the credibility of an influencer when they endorse numerous products within a brief timeframe, as skincare items necessitate an adequate duration for assessing their efficacy.

“ In my experience, I tend to feel skeptical about skincare products that are promoted by influencers who endorse numerous products within a short timeframe. This skepticism arises because skincare items typically require sufficient time for testing. Then, I'm less inclined to repurchase a product that has been heavily promoted in a short period.” [21, M]

Adding further, as the expert mentioned:

“Even when influencers clearly state that a review is sponsored by a specific brand, the sincerity and authenticity of their opinion can usually be detected from their content. When influencers genuinely share their thoughts that align with their personal views, it's clear to the audience. However, if the content seems overly promotional and scripted, it's obvious that it's marketing material provided by the brand.” [22, M]

Expertise

The participants highlighted the expertise of influencers as a factor influencing trust. Interviewees found that professional knowledge brings rapid information flow, interviewees often turn to influencers as trusted sources of skincare advice and product recommendations.

“ Influencers who possess in-depth knowledge about skincare products and can offer personalized recommendations based on their expertise are more likely to sway my purchasing intentions." [22, F]

Due to the extensive array of cosmetics available in the market, items endorsed by influencers are often perceived as more reliable and efficacious.

“ I am often overwhelmed by choice and seek guidance from influencers to make informed decisions. When influencers showcase their expertise through detailed product reviews, skincare routines, and ingredient breakdowns, it makes it easier for me to choose products.” [18, M]

Similarity 

The selection of appropriate products tailored to specific audience profiles of individual influencers holds paramount importance due to variations in their respective demographics. The respondent said: 

“ I often look for influencers that promote drug store cosmetics which suitable with a student like me than one who promotes high-end products” [17, F]

When influencers openly discuss their skincare journey or demonstrate how products address their individual needs, it creates a sense of empathy and understanding among their audience. This sense of kinship encourages consumers to trust the recommendations and consider the products as suitable solutions for their skincare concerns, ultimately driving purchasing intent. One respondent shared:

" Having struggled with acne since my teenage years, I can truly empathize with others who share similar experiences. When I come across Influencers who openly discuss their journey with acne treatment and recommend products based on their trials, I feel a sense of connection and understanding. It's like finding someone who truly gets what you're going through. As a result, I often try out the products they endorse, hoping to find relief from my acne struggles. Their recommendations feel personal and trustworthy, making me more inclined to invest in the same products they've found effective during their skincare journey." [21, F]

Product fit 

Influencers' skin-compatible products serve as clear evidence of the product's alignment with the influencer's skin type.

“ When influencers demonstrate the results and effectiveness of a product on their skin, it implies that the product genuinely suits their skin.” [21, F]

Having influencers use skincare products suitable for their skin condition will make viewers perceive them as more genuine and trustworthy. An interviewee shared:

“It's essential that influencers use products that align with their specific skin concerns. For example, if an influencer struggles with acne, it would be most authentic for them to endorse acne treatment products. Similarly, influencers with melasma should promote products tailored to addressing melasma. This approach ensures that the effectiveness and objectivity of the products are demonstrated, which resonates more strongly with their audience.” [18, M]. 

4. Discussion and implications

Research among students in Hanoi identifies Trustworthiness as the most critical factor driving purchase intentions. This finding aligns with the source credibility model and studies by Pornpitakpan [60] and Gupta et al. [61], which emphasize that honesty, particularly regarding advertising disclosures, instills the confidence necessary for cosmetic purchases. Trustworthiness is not inherent; it requires a duration of impartial product reviews to be verified by consumers, ensuring high objectivity and authenticity. Consequently, influencers who maintain ethical reputations exert the strongest influence on buying decisions.

Similarity is the second most influential factor. As suggested by Martensen et al. [54] and Hudders et al. [62], consumers are more likely to trust influencers they perceive as relatable. In the cosmetics industry, this allows users to visualize product efficacy by following influencers with similar skin tones or concerns. While crucial for niche brands, this factor may hold less weight for mainstream products with broad appeal.

Supplementary factors including Attractiveness, Expertise, and Product Fit further streamline the purchase process. Attractiveness captures initial attention and leverages beauty ideals to foster rapport [63], [64]. However, it is not the primary driver, as consumers ultimately prioritize service quality and rational benefits over physical appearance. Regarding Expertise, while Moore and Yang [65] note that knowledge increases credibility, many Vietnamese consumers downplay this factor since digital influencers often lack formal dermatological certifications. This is exacerbated by the fact that Vietnamese law does not mandate the disclosure of credentials for online reviews [66]. Finally, Product Fit is essential for successful sales. In Vietnam, an influencer’s lifestyle and physical characteristics, such as skin type, must harmonize with the product to enhance persuasiveness and consumer trust.

5. Limitations and future research directions

One limitation of this study is the relatively small sample size, which may affect the generalizability of the findings to the broader population of Gen Z individuals in Hanoi.  Additionally, while the study investigates the direct influence of influencers on purchase intentions on TikTok, it overlooks the potential indirect influence of influencers on purchase intentions. Future research endeavors could consider incorporating moderators or mediators to explore the indirect effects of this association. Lastly, the adoption of mixed methods, while beneficial for comprehensively exploring the research topic, introduces complexities in data analysis and interpretation, posing potential challenges in synthesizing and integrating qualitative and quantitative findings.

A potential future research direction for this thesis could be to investigate the effectiveness of influencer marketing on Gen Z purchase intentions in the cosmetics industry on emerging social media platforms beyond TikTok. As the social media landscape evolves rapidly, platforms like Instagram Reels, Snapchat, and emerging platforms may gain popularity among Gen Z audiences. Exploring how influencer marketing strategies vary across these platforms and their impact on Gen Z's purchasing behaviour could provide valuable insights for marketers and researchers alike. Additionally, further research could delve deeper into the specific types of content or influencer characteristics that resonate most with Gen Z consumers on these platforms, informing more targeted and effective marketing strategies in the cosmetics industry.

References 

[1]. Morgan, A. (2020). Seeking Sales in New Channels: The Effectiveness of Influencer Marketing. Pop Culture Intersections. 49. 

[2]. Geyser, W., (2022). The state of influencer marketing: Benchmark report. Influencer marketing hub, 2.

[3]. Statista. (2020). Most popular beauty brands used among female consumers in Vietnam as of January 2020. Retrieved May 21, 2022, from:

https://www.statista.com/statistics/988870/vietnam-most-popular-beauty-brands.

[4]. Statista, S. (2023) Vietnam: Cosmetics market revenue 2015-2028, Statista. Available at:

https://www.statista.com/forecasts/1259320/vietnam-revenue-cosmetics-market (Accessed: 17 April 2024). 

[5]. Rodrigue, E. (2023, January 16). 31 Influencer Marketing stats to know in 2023. HubSpot Blog | Marketing, Sales, Agency, and Customer Success Content.

https://blog.hubspot.com/marketing/influencer-marketing-stats

[6]. Chen, K.J., Lin, J.S. and Shan, Y., (2021). Influencer marketing in China: The roles of parasocial identification, consumer engagement, and inferences of manipulative intent. Journal of Consumer Behaviour, 20(6), pp.1436-1448.

[7]. Francis, T. and Hoefel, F., (2018). True Gen’: Generation Z and its implications for companies. McKinsey & Company, 12, pp.1-10.

[8]. Morris, N. (2009). Understanding Digital Marketing: Marketing Strategies for Engaging the Digital Generation. J Direct Data Digit Mark Pract 10, 384-387. 

[9]. Duffy, B. E. (2015). The romance of work: Gender and aspirational labour in the digital culture industries. SAGE Journals.

[10]. Rocamora, A. (2018). A labour of fashion blogging, 65-81.

https://www.researchgate.net/publication/325809747_The_Labour_of_Fashion_Blogging

[11]. Enke, N., & Borchers, N. S. (2019). Social media influencers in strategic communication: A conceptual framework for strategic social media influencer communication. International Journal of Strategic Communication, 261-277.

[12]. Wiley, D. (2022) Council post: 6 red-hot influencer marketing predictions for 2022, Forbes. Available at:

https://www.forbes.com/sites/forbesagencycouncil/2022/01/11/6-red-hot-influencer-marketing-predictions-for-2022/?sh=2880d86c1f28 (Accessed: 08 March 2024). 

[13]. Dean, D., Suhartanto, D., and Pujianti, F.N., (2022). Millennial behavioural intentions in Islamic banks: the role of social media influencers. Journal of Islamic Marketing, 13(12), pp.2798-2814.

[14]. Haenlein, M., Anadol, E., Farnsworth, T., Hugo, H., Hunichen, J. and Welte, D., (2020). Navigating the New Era of Influencer Marketing: How to be Successful on Instagram, TikTok, & Co. California management review, 63(1), pp.5-25.

[15]. Wang, Y., (2020). Humor and camera view on mobile short-form video apps influence user experience and technology-adoption intent, an example of TikTok (DouYin). Computers in human behavior, 110, p.106373.

[16]. Daugherty, T., Eastin, M.S. and Bright, L., (2008). Exploring consumer motivations for creating user-generated content. Journal of interactive advertising, 8(2), pp.16-25.

[17]. Casaló, L.V., Flavián, C. and Ibáñez-Sánchez, S., (2021). Be creative, my friend! Engaging users on Instagram by promoting positive emotions. Journal of Business Research, 130, pp.416-425.

[18]. Johnstone, L. and Lindh, C., (2022). Sustainably sustaining (online) fashion consumption: Using influencers to promote sustainable (un) planned behaviour in Europe's millennials. Journal of Retailing and Consumer Services, 64, p.102775.

[19]. Schwieger, D. and Ladwig, C., (2018). Reaching and retaining the next generation: Adapting to the expectations of Gen Z in the classroom. Information Systems Education Journal, 16(3), p.45.

[20]. Nguyen, V. H., Truong, T. X. D., Pham, H. T., Tran, D. T., & Nguyen, P. H. (2021). Travel intentions to visit tourism destinations: A perspective of generation Z in Vietnam. The Journal of Asian Finance, Economics, and Business, 8(2), 1043-1053. 

[21]. Kotler, P., Kartajaya, H. and Setiawan, I., (2021). Marketing 5.0: Technology for humanity. John Wiley & Sons.

[22]. Arilaha, M. A., Fahri, J., & Buamonabot, I. (2021). Customer Perception of E-Service Quality: An Empirical Study in Indonesia. The Journal of Asian Finance, Economics, and Business, 8(6), 287–295

[23]. Wood, S. (2013). Generation Z as consumers: Trends and Innovation. Institute for Emerging Issues: NC State University. 

[24]. Priporas, C.V., Stylos, N. and Fotiadis, A.K., (2017). Generation Z consumers' expectations of interactions in smart retailing: A future agenda. Computers in human behavior, 77, pp.374-381.

[25]. Levin, A. (2020). Influencer marketing for brands. New York:Springer.

[26]. Schivinski, B. and Dabrowski, D., (2016). The effect of social media communication on consumer perceptions of brands. Journal of Marketing Communications, 22(2), pp.189-214.

[27]. Kotler, P., & Armstrong, G. (2010). Principles of marketing. Pearson education.

[28]. Shah, S. S. H., Aziz, J., Jaffari, A. R., Waris, S., Ejaz, W., Fatima, M., & Sherazi, S. K. (2012). The impact of brands on consumer purchase intentions. Asian Journal of Business Management, 4(2), 105-110. 

[29]. Spears, N., & Singh, S. N. (2004). Measuring attitude toward the brand and purchase intentions. Journal of current issues & research in advertising, 26(2), 53-66.

[30]. Ghosh, A. (1990). Ghosh Retail management. Chicago: The Dryden Press series in marketing.

https://www.sciencedirect.com/science/article/abs/pii/0148296395001298

[31]. Shafiq, R., Raza, I. and Zia ur Rehman, M. (2011), Analysis of the factors affecting customers’ purchase intentions: The mediating role of perceived value. African Journal of Business Management Vol. 5(26), pp. 10577-10585.

[32]. Gogoi, B. (2013), Study of antecedents of purchase intentions and its effect on brand loyalty of private label brand of apparel, International Journal of Sales & Marketing, Vol. 3, Issue 2, June 2013, 73-86

[33]. Laroche, M., Kim, C., & Zhou, L. (1996). Brand familiarity and confidence as determinants of purchase intentions: An empirical test in a multiple brand context. Journal of Business Research, 37(2), 115-120.

[34]. Pavlou, P. A. (2003). Consumer acceptance of electronic commerce: Integrating trust and risk with the technology acceptance model. International journal of electronic commerce, 7(3), 101-134

[35]. Statista (2024) Skin care - vietnam: Statista market forecast, Statista. Available at: https://www.statista.com/outlook/cmo/beauty-personal-care/skin-care/vietnam (Accessed: 16 March 2024). 

[36]. Ohanian, R. (1991). The impact of celebrity spokespersons’ perceived image on consumers’ intentions to purchase. Journal of Advertising Research, 31(1), 46-54.

[37]. Ohanian, R. (1990). Construction and validation of a scale to measure celebrity endorsers’ perceived expertise, trustworthiness, and attractiveness. Journal of Advertising, 19(3), 39-52

[38]. Petty, R. E., & Cacioppo, J. T. (1986). The elaboration likelihood model of persuasion. In: Zanna, M. P. (Ed.), Advances in experimental social psychology (Vol. 19, pp. 123–205). Cambridge, MA: Academic Press

[39]. Hovland, C. I., Janis, I. L., & Kelley, H. H. (1953). Communication and persuasion;psychological studies of opinion change.

[40]. Syed, A.A. and Zaidi, H., (2021). Effectiveness of Social Media Influencers in Brand Purchase intentions. International Management Review, p.133.

[41]. Friedman, H. H., Termini, S., & Washington, R. (1976). The Effectiveness of Advertisements Utilizing Four Types of Endorsers.

https://www.semanticscholar.org/paper/The-Effectiveness-ofAdvertisements-Utilizing-Four-Friedman-Termini/d3db28fdf1e813498fb56cf6876b8df52963df54

[42]. Hovland, C. I., & Weiss, W. (1951). The influence of source credibility on communication effectiveness. Public Opinion Quarterly.

43]. Miller, G.P. & Basehart, J. (1969). Source trustworthiness, opinionated statements, and response to persuasive communication. Speech Monographs, 36(1), 1-7.

[44]. Erdem, T. & Swait, J. (2004). Brand credibility, brand consideration, and choice. Journal of Consumer Research, 31(1), 191-198.

[45]. Amos, C., Holmes, G., & Strutton, D. (2008). Exploring the relationship between Celebrity endorser effects and advertising effectiveness: A quantitative synthesis of effect size,

https://www.semanticscholar.org/paper/Exploring-the-relationship-between-celebrity-and-Amos-Holmes/c0c5468eed4abb54600edd86274081db717ac655

[46]. Spry, A., Pappu, R. and Bettina Cornwell, T., (2011). Celebrity endorsement, brand credibility and brand equity. European journal of marketing, 45(6), pp.882-909.

[47]. McGuire, W. J. (1969). Atitudes and Atitude Change.

[48]. Wei, P.S. and Lu, H.P., (2013). An examination of the celebrity endorsements and online customer reviews influence female consumers’ shopping behavior. Computers in Human Behavior, 29(1), pp.193-201.

[49]. Erdogan, B. (1999). Celebrity endorsement: a literature review. Journal of Marketing Management, 291-314.

[50]. Berscheid, E., Dion, K. K., Walster, E., & Walster, G. W. (1971). Physical Attractiveness and Dating Choice: A Test of the Matching Hypothesis. Journal of Experimental Social Psychology, 173-189.

[51]. Kim, Y.J. and Na, J.H., (2007). Effects of celebrity athlete endorsement on attitude towards the product: the role of credibility, attractiveness and the concept of congruence. International Journal of Sports Marketing and Sponsorship, 8(4), pp.23-33.

[52]. Kamins, M. A. (1990). An investigation into the match-up hypothesis in celebrity advertising: when beauty may be only skin deep. Journal of Advertising, 4-13. 

[53]. Speed, R., & Thompson, P. (2000). Determinants of sports sponsorship response. Journal of the Academy of Marketing Science, 226. 

[54]. Martensen, A., Brockenhuus-Schack, S. and Zahid, A.L., (2018). How citizen influencers persuade their followers. Journal of Fashion Marketing and Management: An International Journal, 22(3), pp.335-353.

[55]. Ruef, M., Aldrich, H.E. and Carter, N.M., (2003). The structure of founding teams: Homophily, strong ties, and isolation among US entrepreneurs. American sociological review, 68(2), pp.195-222. 

[56]. Cialdini, R.B., Reno, R.R., and Kallgren, C.A., (1993). The transsituational influence of social norms. Journal of personality and social psychology, 64(1), p.104.

[57]. Kelman, H.C., (2006). Interests, relationships, identities: Three central issues for individuals and groups in negotiating their social environment. Annu. Rev. Psychol., 57, pp.1-26.

[58]. Erz, A. and Heeris Christensen, A.B., (2018). Transforming consumers into brands: Tracing transformation processes of the practice of blogging. Journal of Interactive Marketing, 43(1), pp.69-82.

[59]. Malina, M.A., Nørreklit, H.S. and Selto, F.H., (2011). Lessons learned: advantages and disadvantages of mixed method research. Qualitative Research in Accounting & Management, 8(1), pp.59-71.

[60]. Pornpitakpan, C. (2008). The Effect of Celebrity Endorsers' Perceived Credibility on Product Purchase intentions. Journal of International Consumer Marketing.

[61]. Gupta, R., Kishore, N., & Verma, D. (2015). Impact of celebrity endorsements on consumers' purchase intentions: A study of Indian Consumers. Australian Journal of Business and Management Research.

[62]. Hudders, L. and Lou, C., (2022). A new era of influencer marketing: Lessons from Recent Inquiries and Thoughts on Future Directions. International Journal of Advertising, 41(1), pp.1-5.

[63]. Widyanto, H. A., & Agusti, C. R. (2020). Beauty influencer in the digital age: How does it influence purchase intentions of generation Z. Journal of Digital Marketing and Halal Industry.

[64]. Belch, G., & Belch, M. (2011). Advertising and Promotion: An Integrated Marketing Communications Perspective. New York: McGraw-Hill.

[65]. Moore, A., Yang, K. and Kim, H.M., (2018), January. Influencer marketing: Influentials’ authenticity, likeability and authority in social media. In International Textile and Apparel Association annual conference proceedings (Vol. 75, No. 1). Iowa State University Digital Press.

[66]. Tuoi tre. (2021). Retrieved from tuoitre.vn: https://tuoitre.vn/nguoi-noi-tieng-quang-cao-san-pham-kem-chat-luong-lua-doi-cong-chung-nguoi-tieu-dung-20210513203950743.htm