01What dandruff actually is
Dandruff is generally understood as a mild form of seborrhoeic dermatitis, an inflammatory condition affecting skin rich in sebaceous glands. It is associated with Malassezia, a genus of yeasts that lives on essentially everyone's skin, and it presents as flaking, itch and sometimes redness on the scalp, in the eyebrows, beside the nose, behind the ears and under beards.
Two things follow. It is not caused by poor hygiene, which is the belief most men arrive with, and it is not cured by washing more. It is a condition that is managed, tends to recur, and responds to specific treatment rather than to general cleaning.
02It is usually not a dry scalp
The instinct on seeing flakes is to conclude the scalp is dry and to reach for something moisturising or to wash less often. In seborrhoeic dermatitis the opposite is usually true: the condition favours oily areas, and washing less frequently often makes it worse by allowing sebum and yeast activity to build up.
Genuinely dry, flaking scalp does occur, typically as fine dust like flakes without redness or greasiness, and it does respond to gentler washing and moisturising. Distinguishing the two matters because the treatment runs in opposite directions, and a pharmacist can usually make that distinction quickly.
03What actually works, and how to use it
Antifungal shampoos are the mainstay, and they are available over the counter as well as on prescription in stronger forms. The most common error is using them like a normal shampoo: applying to hair, lathering, rinsing immediately.
The active needs to reach the scalp and stay there. That means parting hair and applying to skin, massaging in, and leaving for several minutes before rinsing, following whatever the product directs. Used two or three times a week initially and then less often for maintenance, this resolves the majority of cases. NHS guidance and NICE clinical knowledge summaries both cover the approach.
04The sulfate free question, which is a different question
Sulfate free shampoo has become the default recommendation for almost every hair complaint, and it is largely unrelated to dandruff. Sulfates are efficient surfactants that can be drying, and milder systems suit some people, particularly those with coloured or textured hair.
Where this causes harm is when a man with seborrhoeic dermatitis substitutes a gentle sulfate free shampoo for an antifungal one and concludes that nothing works. He has changed the cleansing system without addressing the condition. If a milder base suits you, use a milder base and add the antifungal treatment separately. The surfactant argument is in what a face wash is made of, and the chemistry transfers directly.
05When it is not dandruff
Scalp psoriasis produces thicker, more sharply demarcated plaques with silvery scale, often extending past the hairline, and it needs different treatment. Fungal infection of the scalp, more common in children, produces patchy hair loss with scaling. Contact allergy to a hair product produces redness and itch that follows the distribution of application.
Any scalp complaint that does not respond to a properly used antifungal shampoo within a few weeks, or that involves hair loss, pain, pustules, bleeding or spreading beyond the scalp, should be assessed by a pharmacist or GP. The British Association of Dermatologists publishes patient information on each of these.
06Scalp health and hair loss are separate questions
Men frequently conflate the two, partly because a visibly flaking scalp draws attention to thinning hair. Seborrhoeic dermatitis does not cause male pattern hair loss, and treating it will not reverse thinning, though reducing inflammation and itch removes scratching, which is worth doing on its own terms.
Male pattern hair loss has its own evidence base and its own treatments, most of which are medicines rather than cosmetics. We deal with what is evidenced and what is sold in that article, including the growing category of clinic based procedures.
07Washing frequency, which nobody agrees on
There is no universally correct washing frequency. Scalp sebum production, hair type, training frequency, product use and occupation all bear on it. What can be said is that the common advice to wash hair as infrequently as possible is poorly suited to men with oily scalps or seborrhoeic dermatitis, and reasonably suited to men with dry, textured or coarse hair.
The scalp is skin and follows skin logic. If it is oily, wash it. If it flakes and is red, treat it. If it is dry and tight, wash it less and gently. Hair condition is a separate variable and is usually managed at the lengths rather than at the root.
08The scalp nobody protects
A thinning or shaved scalp receives direct overhead ultraviolet exposure and is one of the sites where men develop sun damage and skin cancers. It is also a place most men never look at and never protect, and hair provides less protection than assumed once density falls.
A hat is the most reliable answer, and sun protection formulated for scalp application is the alternative. This is a small point with a disproportionate consequence, which is why it appears again in sunscreen for men.
09The environmental footnote
Shampoo is mostly water in a plastic bottle, which makes it one of the better candidates for concentrate and solid formats. The complication for anyone treating a scalp condition is that the products with the evidence behind them are usually conventional liquid formats, and substituting a solid bar for an antifungal shampoo trades a treatment for a format.
The reasonable position is to use the treatment that works for the condition and apply the environmental reasoning to everything else in the bathroom. The formats and where they genuinely help are assessed in solid bars and waterless formats.