Terpenoids, a diverse class of naturally occurring organic chemicals derived from terpenes, are found in many essential oils and plant extracts. Their use in treating or supporting dandruff is supported by some scientific evidence, primarily due to their antimicrobial and anti-inflammatory properties. Certain terpenoids such as thymol (from thyme), menthol (from mint), and tea tree oil constituents (like terpinen-4-ol) have demonstrated effectiveness against Malassezia species, the fungi most commonly associated with dandruff. For example, tea tree oil, which is rich in terpenoids, has been shown in clinical studies to reduce dandruff severity, likely due to its antifungal activity. Similarly, thymol and menthol are included in some anti-dandruff shampoos and have demonstrated in vitro efficacy against dandruff-causing microbes.

However, most evidence comes from small clinical trials, laboratory studies, or is based on the demonstrated properties of individual terpenoids rather than large-scale randomized controlled trials specifically on dandruff. The mechanism of action is thought to involve both direct antifungal effects and reduction of scalp inflammation. While these findings provide a scientific rationale for the use of terpenoid-containing products in dandruff management, more robust clinical trials are needed to firmly establish efficacy and safety. Overall, there is moderate scientific validation for the use of terpenoids in supporting dandruff treatment.