Alpecin double effect shampoo not only effectively stimulates hair growth directly at the roots through continued usage but also treats and removes dandruff in preparation for aplecins active ingredient caffeine to begin working on the hair folliclesthe double effect shampoo begins by loosening any scaly keratinous cells in order to thoroughly remove any dandruff from the scalp this clearing of dandruff from the scalp then leaves the way clear for the active caffeine ingredient