Dandruff: What Causes It and the Shampoo Ingredients That Actually Work

Dandruff isn’t caused by poor hygiene. It’s linked to a yeast that lives on everyone’s scalp, and some people’s skin simply reacts to it more. The right shampoo, used the right way, controls it for most people.

Imagine getting ready for an interview in a dark suit or uniform, and noticing white flakes on your shoulders. You’ve washed your hair every day this week and it seems to get worse. The fix isn’t washing more. It’s choosing a shampoo with the right active ingredient and leaving it on long enough to work.

What causes dandruff?

• An overreaction to Malassezia, a yeast that naturally lives on the scalp
• Seborrhoeic dermatitis, a more inflamed form that can also affect eyebrows, the sides of the nose and behind the ears
• Dry skin, especially in cold weather
• Stress, which can make flare-ups worse
• Reactions to hair products

Shampoo ingredients that work

• Ketoconazole: an antifungal that targets the yeast
• Zinc pyrithione: antifungal and antibacterial
• Selenium sulphide: slows skin cell turnover and fights yeast
• Salicylic acid: helps loosen and lift scale
• Coal tar: slows skin cell growth, though it can stain light hair

How to use them properly

• Massage into the scalp, not just the hair, and leave it on for about five minutes before rinsing
• Use it two or three times a week until flakes settle, then once a week to keep them away
• If one stops working, switch to a shampoo with a different active ingredient
• For curly, coily or tightly textured hair that’s washed less often, dermatologists often suggest using a medicated shampoo once a week, focusing on the scalp, then following with a moisturising conditioner on the lengths

But what if it isn’t dandruff?

See a doctor, nurse or pharmacist if a month of medicated shampoo hasn’t helped, if your scalp is very red, sore, weeping or crusted, or if you have thick, silvery patches (which can be psoriasis), patchy hair loss or scaling on other parts of the body. In children, a scaly scalp with hair loss can be a fungal infection called tinea capitis, which needs tablets rather than shampoo.

Sources: American Academy of Dermatology (Dandruff: how to treat), NHS (Dandruff; Seborrhoeic dermatitis), British Association of Dermatologists. This guide is for general information and does not replace advice from your own nurse, doctor or pharmacist.