Nizoral kills the fungus that causes dandruff. Ketoconazole" keeps nasty dandruff in check so you don't have to keep checking your shoulders.
Directions
Adults and Children 12 years and over: wet hair thoroughly, apply shampoo, generously lather, rinse thoroughly. Repeat. Use every 3-4 days for up to 8 weeks or as directed by a doctor. Then use only as needed to control dandruff.
Children under 12 years: ask a doctor.