The COVID-19 pandemic has forced many brands to stop using cosmetic testers to avoid the risk of spreading the infection, jeopardising the future of cosmetic testing. Consequently, consumers must find alternative methods to conduct their information searches and, more importantly, the prospects of shopping online without going to the store to test the product. With the enormous prospects of social media cosmetic electronic word of mouth (eWOM), it is imperative to examine the influence of cosmetic eWOM on social media and for cosmetic marketers to understand the antecedents that result in cosmetic consumers making a purchase. The adapted information adoption model was validated through structural equation modelling based on 341 eligible surveys. The results confirmed that information quality, source credibility, information usefulness, and information adoption are the key antecedents in eWOM on Instagram when investigating purchase intentions in the colour cosmetic industry. This study is one of the pioneers in empirically testing the relationship between information quality and source credibility on information usefulness and, subsequently, the relationship between information usefulness, information adoption, and purchase intentions in a western market based on the cosmetic industry. These new insights provide practical implications for a cosmetic marketer, suggesting the key variables leading to purchase intentions in cosmetic eWOM, which can be utilised in marketing techniques.