Caffeine -a methylxanthine derived from purine- is found in the various plants (coffee, tea, cola) all over the world and is widely used in cosmetics due to its ability to penetrate in skin barriers. In this paper, the mechanism of broad effects of caffeine on skin and hair is discussed. Commercial use of caffeine in the formulation of cosmetics (e.g. sunscreen products) can effectively reduce Ultraviolet (UV) irradiation side effects and devastating UV induced free radicals. It inhibits

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... diesterase activity, increases the concentration of cyclic adenosine monophosphate (cAMP) and augments apoptosis in damaged keratinocytes of skin. Caffeine inhibits cell cycle and induces apoptosis by inhibition of ataxia-telangiectasia mutated and Rad3-related (ATR), cycle ATR-chk function. On the other hand, Caffeine is topically used in shampoo as an adjuvant for hair loss treatment. Increasing the cAMP concentration caused by caffeine reduces the tension in smooth muscle near the hair follicle and leads to easier delivery of nutrients through blood vessels. It also prevents negative effects of testosterone on hair follicles in men. Most of currently used hair products contain caffeine. Detailed mechanisms of other effects of caffeine in this field are also discussed.