1st effect: The Double-Effect Caffeine Shampoo loosens scaly, keratinous cells and thoroughly removes dandruff from the scalp. The combination of two effective anti-dandruff substances, salicylic acid and piroctone olamine, has the following benefits: Gentle dandruff removal, Anti-inflammatory action, Antioxidant effect, i. e. improved resistance, Antimicrobial properties. In the past, this combination was only available in pharmacy products as a dermatologically based anti-dandruff solution. It allows precise and gentle micro-peeling (micro-exfoliation) and relieves scalp itch. 2nd effect: The removal of dandruff from the scalp prepares the way for the Caffeine Complex. Alpecin Double-Effect Caffeine Shampoo contains highly dosed caffeine that travels all the way along the hair during washing. It can be detected just 120 seconds after applying.