Hair

The scalp is skin. What to look for in a shampoo INCI

12 September 2026

Scalp skin differs from facial skin in three ways: it has the highest density of sebaceous glands on the body, it is mostly covered by hair, and we treat it with products chosen for the hair, not for the skin itself.

That last point is the source of most problems.

Three questions for every shampoo formula

1. Which surfactants, and in what company?

SLS (Sodium Lauryl Sulfate) is an effective but irritating detergent — used in dermatology studies as a standard irritant to provoke controlled irritation. That says enough about its profile.

Milder alternatives worth looking for:

• —Sodium Lauroyl Methyl Isethionate — an isethionate, very mild, with a dense creamy foam, well tolerated by a sensitive scalp.
• —Sodium Methyl Cocoyl Taurate — a taurate that still cleanses in hard water, because it resists calcium ions.
• —Lauryl Glucoside — a non-ionic glucoside that lowers the irritancy of the whole system.
• —Polyglyceryl esters (Polyglyceryl-6 Caprylate, Polyglyceryl-4 Caprate and related) — mild emulsifiers and solubilisers that soften the whole cleansing blend.

Practical rule: a mix of several mild surfactants almost always irritates less than one strong one, at comparable cleansing power.

2. What pH?

The scalp, like the rest of the skin, is acidic. Hair is even more so — keratin’s isoelectric point sits around pH 3.7. An alkaline shampoo alkalises the scalp and makes the fibre swell.

The problem: brands rarely print pH on the pack. An indirect clue is citric acid in the INCI, plus a preservation system based on benzoic and dehydroacetic acid. Those preservatives work only in acidic pH, so their presence gives away that the formula is acidic.

3. Is there anything that works with the water?

Few people think about this, and it matters — especially in hard-water cities. Calcium and magnesium ions react with anionic surfactants and deposit on hair and scalp. Look for chelating ingredients: Trisodium Ethylenediamine Disuccinate (EDDS), Sodium Phytate, Sodium Gluconate. More on that in a separate article.

What to avoid with specific problems

Oiliness: paradoxically — strong detergents. Aggressive degreasing provokes compensatory sebum. Mild washing, more often, usually works better than a harsh wash used less often.

Itch and flaking: high pH, alkaline soaps, hot water, denatured alcohol high in the INCI.

Fine hair and “no volume”: heavy silicones and mineral oils applied at the roots. The issue is not silicone itself, but where it sits.

Prebiotics — a new category in scalp care

The scalp has its own microbiome, dominated by Cutibacterium and Staphylococcus bacteria and Malassezia yeast. Flaking correlates with a shift in those proportions.

Prebiotic ingredients — such as inulin — do not kill microorganisms; they support the ones you want. That is a different approach from classic anti-dandruff shampoos, whose mechanism is to suppress Malassezia. Both have a place, in different situations. A cosmetic does not treat dandruff; it can support scalp microbiome balance.