An anti dandruff shampoo works by reducing the Malassezia yeast that lives on everyone's scalp and by lifting the flakes that come with it, which is why the active ingredient matters far more than the brand on the bottle. The four worth paying for are zinc pyrithione, piroctone olamine, salicylic acid and, for some people, tea tree oil. Contact time matters as much as the formula, and most people rinse it away far too quickly for it to do anything.

What does an anti dandruff shampoo actually do?

Three things have to line up for dandruff to appear. There has to be sebum, the oil your scalp produces. There has to be Malassezia, a yeast that feeds on that oil and lives on essentially every adult scalp on earth. And there has to be a personal sensitivity to what the yeast leaves behind, mainly free fatty acids, which irritate the skin barrier in some people and not others.

If you want the fuller picture of what lives on the skin up there and why it tips over, we covered the scalp microbiome and why it flakes separately.

That last point is the one nobody tells you, and it explains why two people can carry the same amount of yeast and only one of them flakes. Dandruff is a sensitivity, not an infection. You are not dirty, and you did not catch it.

Skin normally sheds in single cells you never see. When the barrier is irritated, the scalp speeds that cycle up, cells clump together instead of shedding one by one, and those clumps are the flakes on your shoulders. So a shampoo has two jobs: reduce the yeast population, and physically clear the build-up already sitting there.

Which anti dandruff shampoo ingredients are worth paying for?

Ignore the front of the bottle and read the ingredients list. Almost every mainstream product in this category is built on one of a handful of actives, and the marketing around them varies far more than the chemistry does.

If flaking has been going on for months and nothing in that table is shifting it, a pharmacist can point you to stronger products kept behind the counter. Those are medicines rather than cosmetics, they need a pharmacist's advice, and we are not the right people to be recommending them to you.

How should you use an anti dandruff shampoo?

Technique changes the outcome more than the price does. Four rules cover almost every case.

One, put it on the scalp, not the hair. Shampoo is a skin cleanser. Section the hair, apply to the skin with your fingertips rather than your nails, and let the lather run down the lengths on the way out.

Two, leave it on. Three to five minutes. Wash your body, shave, do whatever else needs doing, then rinse. A ten second lather and rinse gives the active almost no contact with the skin, which is why so many people conclude a product does not work when they have never really used it.

Three, use it often enough to matter. Two or three washes a week while flaking is active, then dropping back to once a week as maintenance. Stopping entirely the week it clears is the classic mistake, because the yeast is still there and the flaking simply returns.

Four, rotate. Scalps often stop responding to the same active after a few months. Swapping between a zinc pyrithione product and a piroctone olamine one, rather than escalating to something stronger, resolves a surprising amount of apparent resistance.

What if your anti dandruff shampoo has stopped working?

Work through this order before assuming you need something stronger.

Check the contact time first, because it is the answer more often than anything else. Then check whether you actually have dandruff at all: flakes that are white, small, dry and come with a tight rather than itchy feeling usually mean a dry scalp, and an active that strips oil will make that worse week on week. We wrote a separate piece on how to tell a dry scalp apart from dandruff because getting this wrong is the most expensive mistake in the category.

Next, look at what else is going on the scalp. Heavy styling products, dry shampoo used several days running and silicone-rich leave-ins all leave residue that reads as flaking. A clarifying wash once a fortnight often solves what looked like a stubborn dandruff problem.

Then consider whether this is seborrhoeic dermatitis rather than ordinary dandruff. The two sit on the same spectrum, but seborrhoeic dermatitis brings redness, greasy yellowish scale, and often involvement of the eyebrows, the sides of the nose or behind the ears. Our guide to a seborrhoeic dermatitis flaky scalp covers what that needs.

Does your hair type change the choice?

It changes the schedule more than the active. Anti dandruff actives are drying by design, and hair that is already fragile pays for that.

Afro, coily and tightly curled hair. Washing two or three times a week is often unrealistic and unkind to the hair. The usual compromise is to use the active shampoo on the scalp only, once a week, with a gentler cleanse and a good conditioner in between, and to accept slightly slower progress in exchange for keeping the length intact.

Colour-treated hair. Some actives dull colour and some sulphate-heavy formulas strip it. Apply to the scalp, keep the lather off the lengths, and follow with conditioner from the mid-lengths down.

Fine hair. Residue shows quickly, so the lighter piroctone olamine formulas usually suit better than heavy medicated ones.

Long hair. The ends are the oldest part of the hair and have nothing to do with the scalp problem. Protect them: conditioner every wash, and never drag an active shampoo through the length.

What do Watermans products do here, honestly?

We do not make an anti dandruff shampoo. Nothing in our range contains an antifungal active, so if you are flaking, the product that clears it will come from somebody else, and that is fine. Where we help is the other half of the routine: the gentle wash on the days you are not using the active one, and the conditioner that keeps the lengths from paying for a scalp problem.

Grow Me Shampoo, for the washes in between

Sulfate-free, so it cleans without stripping the scalp further on the days you are not using an active shampoo. Useful if flaking has left your scalp tight and reactive, and worth keeping to the scalp with a light touch rather than scrubbing.

Condition Me Conditioner, mid-lengths and ends only

Anti dandruff actives are drying, and the length takes the hit long before the scalp does. Conditioning from the mid-lengths down every wash reduces breakage and keeps the hair feeling normal while you sort the skin out.

Watermans products are 100% cosmetic and do not treat medical hair loss. Individual results may vary.

Does dandruff cause hair loss?

Not directly, and this distinction is worth being precise about because three different things get muddled together.

Hair loss means follicles producing thinner hair or stopping altogether, as in androgenetic alopecia. Dandruff does not do this.

Hair shedding means more hairs leaving the head than usual because the growth cycle has been disturbed, by illness, stress, childbirth or a crash diet. Severe scalp inflammation can nudge this along, and it settles when the inflammation does.

Hair breakage means the fibre snapping along its length. This is the one dandruff genuinely contributes to, indirectly: scratching an itchy scalp damages the hair at the root end, and the harsh washing routines people adopt out of frustration do the rest.

So the honest answer is that clearing the flaking protects the hair you have. It does not change what the follicle is doing. If your parting is widening or you can see more scalp than you used to, that is a separate question, and a GP is the right first stop.

When should you stop shopping and see someone?

Speak to a pharmacist or book time with your own GP if the scalp is raw, bleeding or weeping; if the scale is thick, silvery and sharply edged, which points towards psoriasis rather than dandruff; if there are painful spots or pustules; if flaking appeared alongside a new medicine; if patches of hair are missing rather than thinning evenly; or if six weeks of consistent, correct use has changed nothing.

We do not run clinics and we cannot assess a scalp we have not seen. What we can tell you is that persistent scalp problems are common, unglamorous and very fixable with the right help, and that most people wait far longer than they need to.

Frequently asked questions

How long should an anti dandruff shampoo take to work?

Most people see a real reduction in flaking within two to three weeks of correct use, meaning two to three washes a week with three to five minutes of contact time. If nothing at all has changed after six weeks, the product or the assumption behind it is wrong.

Can I use an anti dandruff shampoo every day?

You can, but most people do not need to and the scalp often gets drier and itchier as a result. Two or three times a week while flaking is active is enough for the majority, dropping to once a week once it is under control.

Does dandruff mean my hair is dirty?

No. Dandruff is a reaction to a yeast that lives on clean and dirty scalps alike. Washing too rarely can let oil and scale build up, but the flaking itself has nothing to do with hygiene, and plenty of people who wash daily have it.

Why does my dandruff get worse in winter?

Cold outdoor air, indoor heating and hotter showers all dry the skin barrier, and an irritated barrier flakes more readily. Stress and less daylight seem to play a part too. Many people need the active shampoo more often between November and March and less in summer.

Is dandruff contagious?

No. The yeast involved already lives on everyone's scalp, so there is nothing to pass on. Sharing a hairbrush or a pillow will not give somebody dandruff.

Do natural remedies work instead?

Tea tree oil has modest evidence behind it and is the most credible of the natural options. Apple cider vinegar, coconut oil and lemon juice do not reduce yeast in any meaningful way, and the oils can feed it. If you prefer a plant-derived route, a proper tea tree formulation is a fairer test than a kitchen cupboard.

Should I switch shampoo if the flaking comes back?

Coming back is normal, because dandruff is managed rather than finished. If it returns while you are still using the product, rotate to a different active before you escalate. If it returns after you stopped, you probably just need to go back to a weekly maintenance wash.

Can children use a dandruff shampoo?

Flaking on a child's scalp is more often cradle cap or another skin condition, and children's skin is more delicate. Speak to a pharmacist or your GP rather than reaching for an adult product, and do not use one on a baby.

Sources and references

• NHS guidance on dandruff, for the description of the condition, self-care advice and the signs that warrant seeing a GP.
• NICE Clinical Knowledge Summaries on seborrhoeic dermatitis, for the overlap between ordinary dandruff and the inflammatory end of the same spectrum.
• British Association of Dermatologists public information leaflets on scalp conditions, for the distinction between dandruff, psoriasis and eczema of the scalp.
• The peer-reviewed literature on Malassezia and dandruff in the Journal of Investigative Dermatology and the International Journal of Cosmetic Science, for the yeast, sebum and individual susceptibility model and for the comparative evidence on zinc pyrithione and piroctone olamine.

The short version

Choose an anti dandruff shampoo by its active ingredient rather than its advertising, start with zinc pyrithione or piroctone olamine, apply it to the scalp instead of the hair, and leave it on for three to five minutes before rinsing. Use it two or three times a week until the flaking settles, then once a week to keep it settled, and rotate actives if it creeps back. If your flakes are dry and small with no oiliness, you are probably dealing with a dry scalp instead and need the opposite approach. If the scalp is raw, spreading or unchanged after six weeks, stop shopping and speak to a pharmacist or your GP.

Watermans is vegan, UK made, and has sold over 5 million bottles since 2012.