Insights into Tanning Biology and Tanning Products.
This systematic review, conducted following PRISMA guidelines, synthesizes findings from 68 peer-reviewed studies examining the mechanisms, clinical applications, formulations, and adverse effects of four major sunless tanning agents: dihydroxyacetone (DHA), melanotan (I and II), forskolin, and carotenoids. The authors found that DHA produces skin pigmentation through the Maillard reaction (a non-enzymatic browning of amino acids in the stratum corneum) and has shown additional dermatologic utility in vitiligo and erythropoietic protoporphyria, as well as potential antifungal properties—though concerns about cytotoxicity, genotoxicity, and systemic absorption were noted. Melanotan I and II, which act on melanocortin receptors, were associated with serious adverse effects in unregulated use, including rhabdomyolysis, renal infarction, and priapism. Forskolin was reported to stimulate melanin production independently of melanocortin receptors, with efficacy demonstrated primarily in animal models. Orally ingested carotenoids were found to accumulate in skin and subcutaneous fat, producing a yellow-orange hue. The review acknowledges significant limitations: lack of standardized reporting, heterogeneous outcomes across studies, and insufficient long-term human safety data, particularly for forskolin and carotenoids. The authors conclude that further rigorous clinical research and updated regulatory guidance are needed.
Why this grade: This is a systematic review synthesizing 68 peer-reviewed studies; it does not generate original human trial data, so evidence strength is dependent on the quality and design of the underlying included studies, which the authors note were heterogeneous and lacked standardization.
Objective This systematic review aims to critically assess the literature on the mechanisms of action, clinical uses, formulation strategies, and adverse effects of self-tanning agents, with a focus on dihydroxyacetone (DHA), melanotan, forskolin, and carotenoids. Methods A systematic literature review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were screened for relevance to the mechanisms of action, clinical applications, chemical formulations, or adverse effects of self-tanning molecules. A total of 68 peer-reviewed studies were included. Results DHA induces pigmentation via the Maillard reaction and has demonstrated additional dermatologic applications, including use in vitiligo and erythropoietic protoporphyria and as a potential topical antifungal. Concerns persist about DHA-related cytotoxicity, genotoxicity, and systemic absorption. Unregulated melanotan I and II use has caused serious adverse effects, including rhabdomyolysis, renal infarction, and priapism. While forskolin stimulates melanin production independently of melanocortin receptors and has demonstrated efficacy in animal models, carotenoids, when ingested orally, accumulate in skin and subcutaneous fat, creating a yellow-orange hue. Both agents remain underresearched in human populations. Limitations Limitations include lack of standardized reporting across included studies, variability in study outcomes, and limited long-term safety data. Conclusion Sunless tanning agents offer UV-free alternatives for cosmetic pigmentation but are not without risk. While DHA and melanotan remain the dominant agents in current use, forskolin and carotenoids offer alternative pathways for pigmentation and photoprotection. Further clinical studies are necessary to evaluate long-term safety, efficacy across skin types, and formulation optimization. Regulatory frameworks and dermatologic guidance must evolve to reflect the expanding landscape of sunless tanning modalities.
Educational summary of published research — not medical advice. Full text is shown only where licensing permits.