Alpecin Double-Effect Caffeine Shampoo counteracts two hair problems simultaneously. 1st effect: Alpecin Double-Effect Caffeine Shampoo loosens scaly, keratinous cells and thoroughly removes dandruff from the scalp. 2nd effect: Alpecin Double-Effect Shampoo contains highly dosed caffeine that penetrates into the hair roots already during hair washing. In the hair root, the active ingredient forms a 24-hour depot, thereby protecting the hair root from premature inactivity.