Caffeine promotes hair growth and has been proven in numerous Alpecin studies to slow down hereditary hair loss. The active ingredient combination goes directly to the hair roots during daily hair washing. Within just 120 seconds, the caffeine travels along the hair shaft directly into the hair follicles. If the shampoo is left on the scalp for longer, the caffeine will also penetrate into the skin around the hair roots.   How to use: Washing your hair daily with Alpecin Caffeine Shampoo C1 directs the activating ingredient straight to the roots. Leave on the scalp for 2 minutes each day from application to rinsing out.