Dandruff usually means visible flakes, with or without itch. A dry or irritated scalp can itch just as much with little or no flaking. The practical tell is flakes that keep coming back. If the scalp itches but looks clear, something else is likelier. This is a rough guide, not a diagnosis.

I run Lifelong, a refillable deodorant brand. I am not a doctor, dermatologist or trichologist, and this is not medical advice. Below is what the NHS, the British Association of Dermatologists and published research say, and where the evidence is thin I say so.

What is dandruff, actually?

The NHS describes dandruff as a common skin condition that is not harmful and that you cannot catch. It causes white flakes of skin on the scalp and in the hair, which are often more noticeable in darker hair, and the scalp may feel dry and itchy.

The common belief is that it is simply dry skin. The NHS does not say that. It lists a dry scalp as a symptom, and gives the possible causes as a yeast that lives naturally on skin and skin conditions such as eczema. It also says dandruff is not caused by poor hygiene, although flakes may be more obvious if you do not wash your hair regularly. Stress and cold weather may make it worse.

Where the evidence points

The British Association of Dermatologists (BAD) goes into more detail in its 2023 patient leaflet on seborrhoeic dermatitis. It describes dandruff as seborrhoeic dermatitis of the scalp, affecting almost half of all adults. The yeast Malassezia is present on normal skin but found in higher amounts in seborrhoeic dermatitis. Current thinking, it says, is that skin barrier abnormalities and increased sensitivity to oleic acid produced by the yeast lead to inflammation. It adds that the cause is still being researched.

A 2013 review in Acta Dermato-Venereologica (Schwartz and colleagues) agrees the picture is incomplete, but says Malassezia appears to help trigger inflammatory and skin-overgrowth responses. So dandruff is not just dryness, and the mechanism is not fully settled either. For the cleansing side of an oily scalp, see the ingredients that matter in a shampoo for an oily scalp; that is about washing, not treating a condition.

Dandruff or dry scalp: how to tell

There is no reliable home test, and the NHS says not to worry if you are unsure what is causing yours. This summarises how the NHS, BAD and the Psoriasis Association describe the main look-alikes. Use it to know what to mention to a pharmacist, not to diagnose yourself.

One more the NHS lists: a red or silver rash on the scalp, sometimes with patchy hair loss, can be ringworm (tinea capitis). That is one reason to ask someone rather than guess. Also, the sources draw their lines differently. BAD treats dandruff as the mild end of seborrhoeic dermatitis, while the NHS lists them separately.

Why is my scalp itchy with no dandruff?

This is the case most dandruff articles skip, and it matters, because an anti-dandruff shampoo was designed for flakes. A systematic review of scalp itch (Vázquez-Herrera and colleagues, Skin Appendage Disorders, 2017) says scalp itch is a frequent complaint and splits it into cases with and without visible skin changes. The authors call cases with no identifiable cause the most difficult part of assessment. The causes it lists include:

• Reactions to products, which the NHS describes as red, irritated skin after things like hair dye, sprays, gels or mousses
• Eczema or a sensitive scalp
• Seborrhoeic dermatitis and scalp psoriasis
• Head lice
• Psychological causes, where itch typically shows up as a healthy-looking scalp or scratch marks
• Less often, general medical conditions such as diabetes or thyroid problems

Anxiety-driven scratching is a recognised possibility, not a verdict on anyone. If you suspect a product, my guide to natural shampoo for a sensitive scalp covers ingredients people commonly react to, and what SLS and SLES are explains one of the most-discussed cleansing agents. Irritation from a single ingredient is not unique to the scalp, either; I wrote about the same thing under the arm in why baking soda in deodorant irritates skin.

Heat styling often gets blamed for scalp itch. I could not find good evidence either way, so I will not claim it.

What actually works for dandruff

The NHS advice is to use an anti-dandruff shampoo from a pharmacy or supermarket containing ketoconazole, coal tar or salicylic acid, and to ask a pharmacist how to use it. It suggests up to four weeks, and says you may need more than one type. BAD's leaflet names zinc pyrithione, selenium sulphide and ketoconazole as scalp shampoo ingredients, and salicylic acid as an aid for thick scale.

Which of these are medicines? Ketoconazole is one. Whether a given shampoo is pharmacy-only or prescription-only depends on the product, and the electronic medicines compendium lists Nizoral 2% as prescription-only. Coal tar shampoos are also sold as medicines for scalp conditions. For zinc pyrithione and selenium sulphide I could not confirm the current UK legal position from an official source, so the label and a pharmacist are the authority, not me. I am not recommending any of them.

How well do they work? The best evidence I found is a 2015 Cochrane review of skin antifungals (Okokon and colleagues; 51 studies, 9,052 people) for seborrhoeic dermatitis, which includes but is not limited to dandruff. Ketoconazole 2% was linked to a lower risk of rashes failing to clear at four weeks than placebo, but the evidence was rated low quality. Remission was similar to steroids, with fewer side effects. Most trials ran for about four weeks. BAD adds that there is no cure and flares can return when treatment stops.

Washing frequency and hard water: what the evidence says

Does washing more or less help?

The NHS says poor hygiene does not cause dandruff but that flakes may show more if you do not wash regularly. It gives no recommended frequency. I looked for an independent trial on how often to wash and did not find one; most frequency advice online comes from shampoo makers. BAD suggests a gentle, soap-free wash for affected skin in seborrhoeic dermatitis. Beyond that, ask a pharmacist.

Can hard water irritate the scalp?

The research on hard water and skin is about eczema in babies and children, not scalps. A 2020 study in the British Journal of Dermatology (Jabbar-Lopez and colleagues, 1,303 infants) found no clear overall link between harder water and eczema, though risk was higher in babies carrying filaggrin gene variants. The 2011 SWET trial (Thomas and colleagues, PLoS Medicine) found water softeners gave children with eczema no benefit over usual care. I found nothing on hard water and scalp irritation specifically, so it is possible but unproven. If you use a bar, how a shampoo bar behaves depends on your water.

When to see a pharmacist or GP

The NHS says dandruff is not usually serious, and a pharmacist is a sensible first stop. It says to see a GP if:

• you still have symptoms after at least four weeks of anti-dandruff shampoo
• your dandruff is bad or your scalp is very itchy
• your scalp is red or swollen
• you have flaky, itchy patches on your face or elsewhere on your body

I would add anything sore, crusty, blistered or weeping, patchy hair loss, or an itch with no visible cause that will not settle. None of these is a reason to panic, only a reason to stop guessing.

Frequently Asked Questions

How do I know if I have dandruff or dry scalp?

There is no reliable home test, and the NHS treats dryness as a symptom of dandruff rather than a separate condition. Flakes that keep returning point towards dandruff. A pharmacist can help if you are unsure.

Why is my scalp itchy but no dandruff?

A 2017 systematic review lists reactions to products, eczema, scalp psoriasis, head lice and psychological causes, among others. Sometimes no cause is found. See a pharmacist or GP if it persists.

How do you get rid of dandruff?

The NHS advises an anti-dandruff shampoo, tried for up to four weeks. BAD says seborrhoeic dermatitis has no cure and can flare again when treatment stops, so the aim is control.

What shampoo is good for dandruff?

The NHS says to look for ketoconazole, coal tar or salicylic acid. Ketoconazole is a medicine, so ask a pharmacist which product suits you.

Is dandruff caused by dry skin?

Not according to the NHS, which lists a yeast on the skin and conditions such as eczema as possible causes. A dry scalp is described as a symptom.

Does washing your hair more help dandruff?

I could not find independent trial evidence on wash frequency. The NHS says poor hygiene does not cause dandruff, though flakes may be more obvious if you wash less often.

Can hard water cause an itchy scalp?

I found no good evidence that it does. Research on hard water relates to eczema in children and the results are mixed.

Is dandruff contagious?

No. The NHS says you cannot catch dandruff.

At Lifelong, we make refillable deodorant today (Luxe £49, Vibes £14.99, refills £8.99). The REEFill line of hand soap, body wash and shampoo launches on Kickstarter in March 2027, with ocean-bound recycled containers and powdered refills in compostable pouches. It is not a treatment for dandruff or any scalp condition. You can sign up for early-bird access at 40% off if you are curious.