Vitamin A in Skin and Hair: An Update

The review "Vitamin A in Skin and Hair: An Update" discusses the role of Vitamin A and its metabolites, retinoic acid and retinal, in skin and hair health. Vitamin A is necessary for healthy skin and hair growth, but both deficiency and excess can be harmful. Retinoic acid regulates hair follicle stem cells, affecting the hair cycle, wound healing, and melanocyte stem cells. It also influences melanocyte differentiation and proliferation. Retinal is crucial for the phototransduction cascade that initiates melanogenesis. The review also explores the effects of ultraviolet irradiation on retinoid metabolism. The authors conclude that Vitamin A regulates the hair cycle, but its effects depend on dose, timing of diet change, and mouse strain. They also note that pharmacological doses of synthetic retinoids can increase hair loss due to telogen effluvium. Future studies are needed to determine the specific retinoid metabolons present in the melanocyte.