Vitamin A and hair health: new insights and therapeutic potentials

Vitamin A, a critical fat-soluble micronutrient, plays a significant role in the maintenance of healthy skin and hair. Its impact on hair health is particularly notable, affecting the hair cycle through the regulation of hair follicle stem cells and melanocyte stem cells. This review highlights recent research into the dual effects of vitamin A—both its deficiencies and excesses—on hair health, and its potential applications in dermatological treatments.
The main active metabolites of vitamin A, retinoic acid and retinal, have been shown to regulate various aspects of hair follicle function. Retinoic acid, for instance, modulates hair follicle stem cells in a dose-dependent manner, influencing hair cycle dynamics, wound healing, and melanocyte function. Furthermore, retinoic acid is involved in melanocyte differentiation and proliferation, showcasing its multifaceted role in skin and hair physiology. Studies have also uncovered that retinal, necessary for the phototransduction cascade initiating melanogenesis, has its levels affected by environmental factors like ultraviolet irradiation. This finding suggests potential new avenues for protecting and enhancing hair health through nutritional and topical means.
Despite the promising aspects of vitamin A in dermatology, both hypo and hypervitaminosis A can have adverse effects. Too little vitamin A leads to follicular hyperkeratosis, while excessive intake can cause hair loss and diminish sebaceous gland function, illustrating the need for balanced vitamin A levels.