Dr.Wolff Alpecin Double Effect Caffeine Shampoo helps to counteracts, the hair loss and dandruff simultaneously. It mainly acts by the two steps as follows: Stage One: The Double Effect Shampoo loosens scaly, keratinous cells and helps remove dandruff from the scalp. Stage Two: With the scalp cleared of dandruff, the caffeine complex can penetrate into the hair root and help strengthen it against hair loss.