Alpecin Caffeine Hair Booster is a cosmetic that will strengthen and thicken your hairstyle . The caffeine it contains supports hair growth directly at the roots for 24 hours. How does Caffeine Hair Booster work? stimulates hair growth, strengthens and thickens the hairstyle, refreshes the scalp with each use, and stimulates the growth of healthy hair bulbs. With regular use of Caffeine Hair Booster, you will quickly see stronger, thicker and healthier hair.