Although regular washing of the hair may wash away the flakes and limit the signs of dandruff, it does not treat the cause. Nizoral anti-dandruff shampoo works by restoring the natural balance of the yeast on the scalp, which is the main cause of the dry, flaky, red, itchy symptoms of dandruff and prevents them coming back. Not all dandruff treatments work this way, which means they are less likely to be as effective. For severe types of dandruff or seborrhoeic dermatitis try Nizoral dandruff shampoo, available in a 100ml bottle over the counter in pharmacies.