This Caffeine Shampoo contains caffeine that can help to stimulate hair growth directly at the roots. A daily wash with Alpecin C1 shampoo immediately provides the hair roots with the activating ingredient. Alpecin Caffeine shampoo Hair Energizer is detectable after being left on for as little as 120 seconds. If left on longer, more caffeine will be absorbed into the scalp. Mens skin is more sensitive than womens skin. This is due to the male hormone testosterone it makes mens skin less robust and weakens its natural protective function significantly. For the scalp, this means that it loses moisture, its cells regenerate too slowly and both skin and hair roots age prematurely, thereby accelerating hair loss. How does Alpecin work? Alpecin Caffeine penetrates even though the shampoo is rinsed out. In just a short time (120 sec.), caffeine travels along the hair shaft directly into the hair follicles. If the shampoo is left on for longer, the caffeine will also penetrate into the scalp. This shampoo does not contain any conditioning agents so your hair will immediately have more grip.