INTRODUCTION
Hair loss is a common dermatologic condition associated with significant psychosocial distress.1 It has been estimated that 50% of men and women suffer from the most common form of hair loss, known as androgenetic alopecia (AGA), by the age of 40.2 Other forms of non-scarring alopecia are telogen effluvium (TE) and alopecia areata (AA). Food and Drug Administration (FDA)-approved hair loss treatments for AGA include topical minoxidil, oral finasteride, and photobiomodulation. Other options are spironolactone, low-dose oral minoxidil, and platelet-rich plasma.3 Specifically for AA, baricitinib, a Janus kinase (JAK) inhibitor, also became FDA-approved in June 2022. This was followed by the approval of ritlecitinib in 2023 and deuruxolitinib in 2024. Other options for hair loss include hair transplants or non-medical cosmetic aids such as scalp colorants, wigs, and hair extensions. Limitations such as drug-related side effects or costs of these treatments remain significant barriers to care.
Caffeine, an alkaloid methylxanthine, has been proposed to stimulate hair growth through inhibition of 5-alpha-reductase and phosphodiesterases, non-selectively.4,5 The inhibition of phosphodiesterase leads to increased intracellular adenylate cyclase activity as well as increased cyclic 3',5'‐adenosine monophosphate (cAMP) levels to provide more energy for the promotion of metabolic and proliferative activities.6 With limited data available on the efficacy of caffeine for hair growth, the objective of this systematic review was to focus on caffeine supplementation and hair growth.
Caffeine, an alkaloid methylxanthine, has been proposed to stimulate hair growth through inhibition of 5-alpha-reductase and phosphodiesterases, non-selectively.4,5 The inhibition of phosphodiesterase leads to increased intracellular adenylate cyclase activity as well as increased cyclic 3',5'‐adenosine monophosphate (cAMP) levels to provide more energy for the promotion of metabolic and proliferative activities.6 With limited data available on the efficacy of caffeine for hair growth, the objective of this systematic review was to focus on caffeine supplementation and hair growth.
MATERIALS AND METHODS
A systematic literature search was performed in August 2023 across seven databases, including PubMed, Medline, and Embase via Ovid, Cochrane Library via Wiley, Scopus, Web of Science Core Collection, and ClinicalTrials.gov. The search strategy employed a combination of natural language searching





