Sensitive Skin Care: How to Spot Irritants in an INCI List

For sensitive skin, four ingredient families are worth checking first on an INCI list: fragrance and its declared allergens, drying alcohols placed high in the list, formaldehyde-releasing preservatives, and concentrated exfoliating acids.

None of these makes a product dangerous. They are things to check, not things to ban — and that distinction is exactly what ingredient blacklists get wrong. Sensitive skin does not react to everything. It reacts to specific things, and those things are usually identifiable on the label.

This article assumes you can already read and decode an INCI list. If not, start there.

What "sensitive skin" actually means

Sensitive skin is skin whose barrier lets external substances through more readily, so it reacts to products that other skin types tolerate without trouble.

That definition matters for two reasons. It explains why sensitivity is a matter of degree rather than a yes-or-no state. And it explains why the ingredients that cause problems are the same ones that penetrate most easily: volatile fragrance, solvents, surfactants.

Three different reactions get confused with each other constantly:

Irritation eases if you reduce the dose or the frequency. Allergy does not: once you are sensitised to a molecule, you stay sensitised, even at trace levels.

The 4 families to check

1. Fragrance and fragrance allergens

Fragrance is the leading cause of contact allergy in cosmetics. The catch-all term Parfum (or Fragrance) can conceal dozens of molecules that are not declared individually.

EU regulation requires recognised fragrance allergens to be declared separately once they exceed 0.001% in a leave-on product or 0.01% in a rinse-off product¹. That list grew from 26 to over 80 substances under Regulation (EU) 2023/1545², with a transition running to 31 July 2028 — so depending on how old the product is, you may see the old list or the new one.

What to look for: Linalool, Limonene, Geraniol, Citronellol, Eugenol, Cinnamal, Benzyl Alcohol, Coumarin.

Seeing these names is not bad news in itself: their presence means the brand is meeting its declaration obligation. What they give you is something usable — you know precisely what you are putting on your skin.

2. Drying alcohols

Not all alcohols are the same, and the confusion is common.

Fatty alcohols carry the word "alcohol" for reasons of chemical nomenclature but behave like emollients. Finding them mid-list is normal and harmless.

For the drying ones, position is everything. Alcohol Denat. in second or third place in a leave-on product is a genuine signal for reactive skin. The same ingredient after the preservative — so below the 1% threshold — has almost no effect.

3. Formaldehyde-releasing preservatives

These preservatives work by slowly releasing small amounts of formaldehyde. They are permitted and regulated in the EU, but they are among the least well tolerated preservatives for reactive skin.

What to look for: DMDM Hydantoin, Imidazolidinyl Urea, Diazolidinyl Urea, Quaternium-15.

By comparison, Phenoxyethanol — capped at 1% in the EU³ — is generally better tolerated, which is why it appears in almost every formula aimed at sensitive skin.

4. Concentrated exfoliating acids

AHAs and BHAs (Glycolic Acid, Lactic Acid, Salicylic Acid, Mandelic Acid) are not off-limits for sensitive skin, but dose and frequency change everything.

Low-percentage mandelic acid once or twice a week is often fine. Concentrated glycolic acid, daily, on an already-compromised barrier, almost never is. The question is not "acid or no acid" but "which one, at what dose, how often".

What tells you nothing useful

Some claims reassure without guaranteeing anything.

• "Hypoallergenic" — no binding legal definition in the EU, no independent verification. The claim commits the brand to nothing.
• "Dermatologically tested" — confirms a test happened, while saying nothing about its protocol or its result.
• "Natural" / "clean" — no regulatory definition, and no bearing on tolerance. Essential oils are natural and rank among the most frequent allergens.

The one genuinely checkable claim is "fragrance-free", because you can verify it yourself on the INCI list: no Parfum, no Fragrance, no separately declared allergen.

How to patch test a new product

If your skin reacts easily, test before putting anything on your face:

1. Apply a small amount to the inner elbow or behind the ear
2. Once a day, for three to five days
3. Watch for redness, itching, dryness or small bumps

Three to five days, not twenty-four hours: a contact allergy often takes 24 to 72 hours to show. A single-day test can miss it completely.

For more on reading a label before you buy, see how to check skincare ingredients before buying a product, and cosmetic ingredients to avoid for the category-by-category detail.

Frequently asked questions about sensitive skin care

What ingredients should sensitive skin avoid?

Four families deserve attention first: Parfum and the individually declared fragrance allergens (Linalool, Limonene, Geraniol, Citronellol, Eugenol), drying alcohols placed high in the list (Alcohol Denat., Isopropyl Alcohol), formaldehyde-releasing preservatives (DMDM Hydantoin, Imidazolidinyl Urea), and high-strength exfoliating acids. None of these makes a product dangerous — they are things to check for position and dose before buying.

Does "hypoallergenic" actually mean anything?

Not in any regulated sense. "Hypoallergenic" has no binding legal definition in the EU and is not verified by an independent body. "Fragrance-free" is far more useful, because you can check it yourself against the INCI list: if there is no Parfum, no Fragrance and no separately declared allergen, the claim holds. Read the ingredient list rather than the front of the pack.

Is a natural ingredient gentler on sensitive skin?

No, and often the reverse. Essential oils are among the most common contact allergens in dermatology: Linalool, Limonene and Geraniol are naturally occurring molecules from citrus, lavender and geranium. Many synthetic molecules, by contrast, are chemically inert and very well tolerated. For reactive skin, where an ingredient came from tells you nothing about how well you will tolerate it.

Should you patch test a new product?

Yes, if your skin reacts easily. Apply a small amount to a discreet area — the inner elbow or behind the ear — once a day for three to five days before putting it anywhere near your face. A contact reaction often takes 24 to 72 hours to appear, so a single-day test is not long enough to conclude anything.

This guide is educational and is not medical advice. If a reaction persists, or in cases of eczema, speak to a dermatologist.

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References / Sources

¹ Regulation (EC) No 1223/2009 on cosmetic products — Annex III, fragrance allergens subject to individual declaration and the applicable thresholds: eur-lex.europa.eu

² Regulation (EU) 2023/1545 amending Annex III — expands the list of individually declared fragrance allergens from 26 to over 80 substances, with a transition running to 31 July 2028: eur-lex.europa.eu

³ CosIng — the EU cosmetic ingredient database, including the EU concentration limit for Phenoxyethanol (Annex V): ec.europa.eu/growth/tools-databases/cosing

⁴ Cosmetic Ingredient Review (CIR) — safety assessments of fragrance materials and contact allergens: cir-safety.org