What Makes a Good Scalp Cleanser?

You wouldn't wash your face with laundry detergent. Yet most of us clean the skin on our head with a product designed for the fibres growing out of it, then act surprised when that skin behaves badly.

That's the whole idea behind a scalp cleanser. It's a face wash for the skin you can't see. Once you know what it's supposed to do, deciding whether the bottle in your hand is any good takes about 15 seconds of label reading.

What is a scalp cleanser, and how is it different from shampoo?

A scalp cleanser is formulated for skin, while shampoo is formulated for hair fibre. That changes almost everything about a scalp cleanser: the texture is thinner so it reaches the roots, the cleansing agents are chosen to lift oil and build-up off the skin, and the active ingredients target itching, flaking or oiliness rather than shine and slip.

Plenty of bottles say shampoo on the front but behave like a cleanser. The word on the label matters far less than what's inside it.

Your scalp is the oiliest skin you own.

Your head has one of the highest concentrations of oil glands on your whole body. Add sweat, dust, dry shampoo, hairspray, a gym cap and a Johannesburg summer, and you're asking that skin to cope with more than your face deals with in a week.

The difference is that you can see your face. Nobody inspects their own scalp. So build-up creeps up slowly, and by the time you notice, it arrives as an itch, a flake, or roots that go greasy a day after washing.

Build-up also comes from places people don't count. Dry shampoo is powder that sits on skin until you wash it off properly. Silicones in conditioner and heat protectant migrate to the roots. Hard water leaves mineral deposits behind. None of these is a problem on its own, but they add up on skin that never gets cleaned properly.

The four things a good one actually does

1. It cleans skin. Thin enough to reach the scalp through your hair, and meant to be worked into the skin rather than piled onto the lengths.

2. It lifts build-up without stripping. Here's the trap almost everyone falls into: Squeaky clean feels like clean, but it means you've stripped the barrier, and a stripped scalp panics and produces more oil. You wash more often, strip it again, and the whole thing loops. A good cleanser leaves your scalp feeling comfortable, not tight.

3. It addresses the cause, not the symptom. Flaking usually isn't dryness. It's most often a yeast called Malassezia that feeds on scalp oil, which is why slathering on oil to fix flakes tends to make things worse.

4. It rinses clean. Anything heavy or waxy that stays behind is tomorrow's build-up.

The best ingredients for scalp health

The best ingredients for scalp health depend on which problem you're solving. 

The 48-hour read

What your scalp does two days after a wash tells you which of the scalp-cleansing products on the shelf is yours.

• Roots greasy, lengths fine. You need clarifying. Something like the KMS Head Remedy Deep Cleanse Shampoo once a week, with your normal wash on the other days.

• Itchy, with small white flakes. That's the yeast, not dryness. Look for zinc pyrithione or piroctone olamine, or the cooling route of Paul Mitchell Tea Tree Special Shampoo.

• Tight and squeaky straight after washing, oily by the next morning. Your cleanser is too harsh, and your scalp is overcompensating. Go gentler for a month.

• Fine, but you're seeing more hair in the drain. Density-focused formulas like the Nioxin System 1 Scalp Cleanser are built for exactly this scenario.

• No complaints at all. Then you don't need a new product. Genuinely.

Does a scalp cleanser for hair growth actually work?

A scalp cleanser for hair growth won't grow hair on its own, but it clears the obstacles. Blocked follicles, chronic inflammation and heavy build-up all make a bad environment for hair, and fixing that gives whatever else you're doing a fair chance. Treat it as the groundwork, not the treatment.

If growth is the actual goal, the cleanser is step one of several. Something like Revita's density shampoo is built for that job, and it works best alongside a leave-in treatment rather than instead of one. Anything promising regrowth from a wash-and-rinse product alone is overselling itself.

How you wash matters more than what you buy

You can own a brilliant cleanser and get nothing from it, because most people wash their hair rather than their scalp.

Put the product on your scalp, not on your lengths. The lengths get cleaned by what runs down during the rinse, which is plenty. Use your fingertips, never your nails, and work in small circles across the whole head, including the back where nobody bothers. A scalp exfoliator and massager does this better than fingers if your scalp needs it.

Give it 60 seconds of contact. Actives need a moment to work, and a three-second lather is a rinse with extra steps. If your hair is properly dirty, wash twice: the first pass lifts the surface, the second one actually cleans.

Use warm water, not hot. Hot water strips oil aggressively and leaves your scalp irritated. Every rule you already follow for your face applies here, too. Two or three washes a week suits most people. Fine or oily hair often needs more, and there's no prize for holding out.

When it isn't the cleanser

Some scalps need more than a better bottle. Flaking that doesn't shift after a month, patches that are red, sore or scaly, sudden heavy shedding, or any actual pain all warrant a doctor rather than another product. Psoriasis, seborrheic dermatitis and fungal infections look similar from the outside and need proper treatment.

Diet plays its part, too, and if you're already down the supplement route, the question of biotin or collagen for hair and skin is worth settling before you buy both.

So: read your scalp on day two, buy for what it's telling you, and put the product where the problem actually is. Everything else is packaging.