Nizoral Anti-Dandruff Shampoo with 1% Ketoconazole (14 fl oz)

If your dandruff laughs at ordinary anti-dandruff shampoo, the cause is usually an overgrowth of Malassezia, a yeast that lives on every scalp and feeds on oil. Zinc-based shampoos slow it down. Ketoconazole is a true antifungal that knocks it back, which is why dermatologists commonly suggest Nizoral for stubborn flaking and for seborrheic dermatitis, the greasy, yellowish scaling that also shows up around the nose, brows and ears.

Best for: oily, itchy scalps with recurring flakes; people who get only partial relief from zinc pyrithione or selenium shampoos; and anyone who wants a treatment used twice a week rather than daily.

Skip it if: your scalp is broken or inflamed, or your flakes are thick, silvery and well defined. That pattern suggests psoriasis, which needs a different plan.

How to use it: every three to four days for up to eight weeks, then as needed. Massage into the scalp rather than the hair, and many dermatologists suggest leaving the lather on for three to five minutes before rinsing. It contains sulfates and fragrance and can dry out curls, color-treated or bleached lengths, so use your normal shampoo and a good conditioner on the other days.

Pros: True antifungal active, stronger approach than zinc shampoos; Twice-weekly use, so one bottle lasts; Large size is better value per ounce than the 7 oz

Cons: Can be drying on curly, coloured or bleached hair; Contains sulfates and fragrance; See a doctor if no improvement in two to four weeks