Most people using anti-dandruff shampoo are using it wrongly, and the mistake is almost always the same: they lather it, rinse it straight off, and conclude after three weeks that it doesn’t work.

These are medicated products. The active ingredient needs time in contact with the scalp to do anything at all — three to five minutes, every time. Rinsing immediately is roughly equivalent to swallowing a paracetamol and spitting it straight back out.

Fix that one thing and a substantial number of dandruff problems resolve without changing product. Where it fits alongside everything else is covered in the scalp care routine guide.

What dandruff actually is

Not dryness, which is the near-universal assumption and the reason so many people reach for a moisturising shampoo and get worse.

Dandruff is usually a mild form of seborrhoeic dermatitis: an inflammatory response to an overgrowth of Malassezia, a yeast that lives on everyone’s skin and feeds on sebum. In some people the scalp reacts to its by-products with inflammation and accelerated skin cell turnover. Cells that should take a month to shed come off in a few days, clumped together with oil — which is what you see on your shoulders.

Which means it’s an oily condition, not a dry one, and it needs an antifungal rather than a moisturiser.

Telling it apart from a dry scalp

Dandruff: larger flakes, often yellowish or greasy, scalp may look red, itching is common, and it tends to be worse in winter and during stress.

Dry scalp: small, white, dry flakes, tight feeling, no redness, usually accompanied by dry skin elsewhere on the body.

If you’ve been treating small dry flakes with a strong antifungal and it’s getting worse, you probably have the second one.

The active ingredients

Ignore the brand on the front. Look at the active ingredient and its percentage on the back.

Ketoconazole (1% over the counter, 2% from a pharmacy). An antifungal, and generally the most effective option for genuine seborrhoeic dermatitis. Twice weekly is typically sufficient.

Zinc pyrithione (1–2%). Antifungal and antibacterial. The most common ingredient in supermarket anti-dandruff shampoos. Gentle enough for frequent use.

Selenium sulphide (1–2.5%). Antifungal, and it also slows skin cell turnover. Effective but can discolour blonde, grey and chemically treated hair, so worth avoiding if that applies to you.

Coal tar. Slows cell turnover. Useful for psoriasis as well as dandruff. Distinctive smell, can stain light hair, and increases sun sensitivity.

Salicylic acid. Not an antifungal — it dissolves and lifts existing scale. Best used alongside an antifungal rather than instead of one.

Tea tree oil. Some evidence of antifungal activity at around 5% concentration. Gentler and less reliable than the pharmaceutical options; a reasonable maintenance choice for mild cases.

How to use it properly

Wet the hair. Apply directly to the scalp, not the lengths — the scalp is where the problem is.

Massage in with your fingertips for a full minute.

Then leave it on for three to five minutes. Time it. This is the entire difference between a product that works and one that doesn’t, and nearly everyone underestimates how long five minutes feels in the shower.

Rinse thoroughly. Condition the mid-lengths and ends only.

Frequency: two to three times a week during a flare. Use a gentle normal shampoo on other days.

Rotating actives

Malassezia can become less responsive to a single active over time, which is why a shampoo that worked brilliantly in January can seem useless by June.

The fix is rotation. Use one active for four to six weeks, switch to a different one, and rotate back. Ketoconazole and zinc pyrithione make a good pair.

Once symptoms are under control, drop to once weekly as maintenance rather than stopping altogether. Dandruff is a condition you manage rather than cure — stopping entirely usually means it returns within a few weeks, which people interpret as the product having failed.

What makes it worse

Stress. Well documented, and one of the more consistent triggers.

Cold weather and indoor heating. Which is why British winters are a reliable flare season.

Washing too little. Sebum feeds the yeast. Counter-intuitively, people with dandruff often need to wash more, not less.

Heavy styling products. Build-up around the follicle worsens everything. A scalp scrub or a regular clarifying shampoo helps here.

Hot water. Strips the barrier and increases irritation.

Diet and alcohol appear to be triggers for some people, though the evidence is inconsistent and it varies individually.

Managing colour-treated and textured hair

Many medicated shampoos are drying and some strip colour. If you colour your hair, avoid selenium sulphide, use the medicated shampoo on the scalp only, and follow with a rich conditioner on the lengths. The maintenance approach in hair colour care becomes more important, not less.

For curly and coily hair, washing two or three times a week may be more than the lengths can tolerate. Apply the shampoo to the scalp only, in sections, and let it rinse through without scrubbing the lengths. Follow with a deep conditioner.

When it isn’t dandruff

This matters, because several conditions look similar and need different treatment.

Psoriasis: thicker, silvery, well-defined plaques, often extending past the hairline. Needs medical treatment.

Contact dermatitis: a reaction to a product ingredient. Redness and itching that started after you changed something.

Tinea capitis: a fungal infection, more common in children, often with patchy hair loss and scaling. Needs prescription treatment — over-the-counter shampoo will not clear it.

Eczema: generally alongside eczema elsewhere on the body.

When to see someone

See a pharmacist or GP if: there’s no improvement after four to six weeks of correct use, including the full contact time; the scalp is painful, oozing, or has pustules; you’re losing hair in the affected areas; the flaking extends onto your face, chest or behind the ears; or the itching is disturbing your sleep.

Pharmacists can supply 2% ketoconazole and are genuinely useful for this — it’s worth a conversation before assuming you need a GP appointment.

This article is general information, not medical advice. Persistent, painful or worsening scalp conditions should be assessed by a pharmacist, GP or dermatologist.