Shampoo for a sensitive scalp: what the ingredient list can show

What a sensitive scalp is, and is not

A sensitive scalp is defined by unpleasant sensations, such as tingling, burning, pain or itch, set off by things that should not cause them, and cosmetics are among the possible triggers. In a study of 133 women, itch was the main symptom.¹

It is not one condition. Dermatologists distinguish a primary sensitive scalp, with no other scalp disease, from a secondary one caused by conditions such as psoriasis, seborrhoeic dermatitis or atopic dermatitis, and no laboratory or biopsy test confirms it.² An allergy is something else again: contact allergy is a lifelong change in how the immune system reacts, and once someone is sensitised, a much lower amount of the allergen can set off symptoms.³ Telling these apart is a dermatologist's job, which is why this page describes what a label shows, not which shampoo to choose.

Fragrance, named allergens and essential oils

A review of hair cosmetics ranks fragrances first among the causes of reactions to cosmetic ingredients, ahead of hair dyes and preservatives. It adds that most cases come from leave-on products, and that products in brief contact with skin usually do not cause irritation or allergy.⁴

On an EU label, a perfume and its raw materials appear as Parfum or Aroma, followed by any substances that must be named separately.⁵ In a rinse-off product such as shampoo, a fragrance allergen must be named when it exceeds 0.01%³: Linalool, for example, is Annex III, entry 84, and Limonene entry 88.⁶ The rule exists so that people who already know their allergy can avoid it; the EU estimates that 1-9% of its population is allergic to fragrance allergens.³

The list grew in 2023: to the 24 allergens already named, the EU added 56 more that its scientific committee had identified, including some essential oils.³ Mentha Piperita Oil, peppermint oil, is now Annex III, entry 361, and lavender oils are entry 360.⁶ Products placed on the market after 31 July 2026 must follow the longer list, but older stock may be sold until 31 July 2028³, so a pack on the shelf can name fewer allergens than a newer one. EU fragrance allergen labels explains the list.

Preservatives: what changed for methylisothiazolinone

Methylisothiazolinone (MI), a preservative⁷, shows how rules change because of allergy. In 2016 the EU banned it from leave-on products: its scientific committee had found no safe concentration for leave-on products adequately demonstrated, and the EU pointed to an increased incidence of allergies.⁸ In 2017 it cut the rinse-off limit from 0.01% to 0.0015%.⁹ Today MI is Annex V, entry 57: rinse-off products only, up to 0.0015%.⁶

MI also comes in a mixture with Methylchloroisothiazolinone, labelled Methylchloroisothiazolinone (and) Methylisothiazolinone: Annex V, entry 39, rinse-off products only, up to 0.0015% of a 3:1 mixture. The two entries are mutually exclusive, so a product may not add MI on its own to the mixture.⁶ When the mixture was restricted to rinse-off products in 2014, the EU's scientific committee had indicated that an allergy is less likely to start, or to flare, from a rinse-off product than from a leave-on one at the same concentration.¹⁰

Formaldehyde-releasing preservatives carry a warning instead. After 31 July 2026, every product on the EU market whose preservatives release more than 0.001% formaldehyde in total must be labelled "releases formaldehyde".¹¹⁶

Cleansers can turn up in patch tests too

Fragrance and preservatives are not the only names patch tests find. Of more than 24,000 patients tested by a North American dermatitis group, 2.0% reacted to Decyl Glucoside or lauryl glucoside, two non-ionic cleansers, and hair products were the most common source named.¹² Cocamidopropyl Betaine has its own page on what patch tests show.

What the label cannot show

• How much. A list gives no concentrations, and an allergen below the labelling threshold need not be named at all.³
• Your own allergies. Allergen labelling helps people who already know what they react to.³
• The cause of your symptoms. A sensitive scalp has no objective laboratory test², and contact allergy is diagnosed by patch testing.¹³

Patch testing belongs with a dermatologist. The European Society of Contact Dermatitis guideline covers it for people suspected of allergic contact dermatitis, including testing products a patient brings in.¹³ A shampoo is not tested as it comes: it has to be diluted first, irritation can still give false positives, and testing its ingredients one by one gives a better answer.¹⁴

What to look for on the label

• Parfum, Fragrance or Aroma, and the allergen names after it. The checker's Fragrance and Fragrance allergens groups mark them.
• Plant oils with a scent, which the Essential oils group marks. Some, like peppermint oil, are also named allergens.
• Preservatives, often near the end: Methylisothiazolinone, Methylchloroisothiazolinone, and the warning "releases formaldehyde". The Formaldehyde releasers group marks preservatives labelled as releasing it.
• A name you already know you react to. Search the list for it in the shampoo ingredient checker, which matches label variants of a name to the same ingredient.

This page describes labels, not your scalp. It does not recommend any product or ingredient as suitable for a sensitive scalp, and it is not medical advice: if your scalp reacts, see a dermatologist.