Endocrine disruptors in cosmetics: what is real and what is alarmism

Endocrine disruptors are substances that interfere with hormonal function. Some were present in cosmetics and have been progressively restricted or banned in the European Union, which has the world's most demanding cosmetics regulation — over 1,600 prohibited substances, against barely a dozen in the United States. The most recent case is TPO, banned in gel nail products since 1 September 2025. But not everything circulating as dangerous actually is: tocopherol, one of the most flagged ingredients in cosmetic-scanning apps, is simply vitamin E.

What are endocrine disruptors?

They are substances able to interfere with the hormonal system, mimicking natural hormones, blocking their receptors, or altering how they are produced and cleared.

Interest in them in cosmetics rests on two points. The skin absorbs part of what is applied, and cosmetic products are used daily, for decades — which raises the question of cumulative exposure and the combined effect of several substances.

At the same time, precision matters: classifying a substance as an endocrine disruptor is not the same as demonstrating that it causes disease at the concentrations used in a cosmetic. Dose and route of exposure count.

The TPO case in gel nail products

This is the most recent concrete example, and it is worth understanding how it worked.

TPO — Trimethylbenzoyl Diphenylphosphine Oxide — was a photoinitiator used in gel and gel polish. It is the substance that makes the product harden under a UV or LED lamp.

In 2023, the European Chemicals Agency classified it as CMR 1B: presumed carcinogenic, mutagenic or toxic for reproduction, based on animal studies. Commission Regulation (EU) 2025/877 of 12 May 2025 added it to the list of prohibited substances.

Since 1 September 2025, the sale and use of cosmetics containing TPO is prohibited in the European Union, including in professional settings. Before that it was permitted at up to 5% in professional artificial nail kits.

How to check: look in the INCI ingredient list for Trimethylbenzoyl Diphenylphosphine Oxide or Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide. They are the same compound.

Beware a similar name: Bis-Trimethylbenzoyl Phenylphosphine Oxide is not covered by the ban. It is a different substance. The similarity of the names has caused confusion in salons and on social media.

If you had manicures with TPO-containing products before the ban, there is no cause for alarm: the concentration was low and exposure intermittent. The measure is precautionary and applies going forward.

Is tocopherol harmful? And tocopheryl acetate?

No. And this is probably the most widespread confusion in cosmetics.

Tocopherol is vitamin E. Tocopheryl acetate is its esterified, more stable form. They are antioxidants, used precisely to protect the formulation from oxidation and to benefit the skin.

The alarm comes from label-scanning apps that assign negative ratings using opaque criteria, sometimes confusing chemical names with toxicity. An ingredient with a complicated name is not dangerous for that reason — and water, on a label, is called aqua.

Vitamin E can, very rarely, cause contact dermatitis in sensitised individuals. That is an individual allergy, not a general risk.

What about methylisothiazolinone?

Here the concern is founded, but for a different reason.

Methylisothiazolinone (MIT) is a preservative. It is not classified as an endocrine disruptor or a carcinogen — it is a potent contact allergen.

Its widespread use in leave-on products caused, in the past decade, a genuine epidemic of allergic contact dermatitis across Europe. The regulatory response was to restrict it: it is banned in leave-on products and limited to very low concentrations in rinse-off ones.

Anyone who has reacted to this preservative should avoid it entirely, and that is identified through patch testing in a dermatology consultation.

The distinction matters: allergen, carcinogen and endocrine disruptor are three different things, and they are frequently conflated in the lists circulating online.

Is there a list of toxic ingredients in cosmetics?

There is, and it is official: Annex II of Regulation (EC) No 1223/2009, with over 1,600 substances prohibited in cosmetics in the European Union. Annex III adds those permitted only with concentration or use restrictions.

The lists circulating on blogs and social media are not that list. They tend to mix genuinely prohibited substances with perfectly safe ones, and rarely distinguish the type of risk or the concentration.

A product legally sold in the European Union complies with this regulation. That does not mean zero risk — it means it underwent a safety assessment and contains no prohibited substances.

Are “endocrine-disruptor-free” cosmetics worth it?

The phrase has no legal definition and is largely commercial positioning.

There is no official, closed list of “endocrine disruptors in cosmetics” that a brand could claim to exclude. What exists are prohibited substances — which no legal product contains — and substances under assessment.

The same applies to “paraben-free”. Short-chain parabens, methyl and ethylparaben, are among the most studied preservatives and remain authorised because they are considered safe at permitted concentrations. Long-chain ones were banned. A paraben-free product has replaced them with another preservative — not necessarily better, and possibly more allergenic.

The “natural” label is no guarantee either. Many frequent contact allergens are plant-derived: essential oils, plant extracts, limonene, linalool.

How to read a cosmetic label

• The INCI list appears in descending order of concentration down to 1%; below that, the order is free

• Fragrance allergens requiring declaration appear at the end: limonene, linalool, citronellol, geraniol, among others

• Aqua is water. Tocopherol is vitamin E. Ascorbic acid is vitamin C

• An open-jar symbol with a number — 6M, 12M — indicates the period after opening

• Products legally sold in the EU state the responsible person and the batch number

If you have known allergies, the label is your main tool. If you do not, reading labels with a rating app tends to generate more anxiety than safety.

What to do, in practice

Buy through legal channels. Products bought outside the European Union, on unregulated platforms or without local-language labelling may not comply with European legislation.

For gel nails, confirm the salon no longer uses TPO-containing products. It is reasonable to ask, and the professional should know the answer.

Simplify your routine. The fewer products, the lower the chance of sensitisation. Ten-step routines multiply exposure to allergens without proportional benefit.

Test new products on a small area, behind the ear or on the forearm, for a few days, particularly if you have sensitive skin.

Report to the competent authority any product you suspect does not comply, or any adverse reaction. In Portugal that is INFARMED, and reporting feeds the vigilance system.

When to see a dermatologist?

• When a product causes redness, itching, burning or a rash

• When you react to several different products and cannot identify the culprit

• When you want to know which substance you are allergic to — patch testing gives that answer

• When you have dermatitis on the hands, face or eyelids with no apparent cause

• When you reacted after a gel manicure or artificial nail application

• Before investing in a complex routine, if your skin is reactive

Dr Ellene Papazis is a dermatologist accredited in Portugal and Brazil. Consultations in Porto, Portugal.

Sources

• Regulation (EC) No 1223/2009 on cosmetic products — Annexes II and III

• Commission Regulation (EU) 2025/877 of 12 May 2025 — prohibition of TPO

• European Chemicals Agency (ECHA) — CMR classification of TPO

• INFARMED — competent authority for cosmetics in Portugal

• Scientific Committee on Consumer Safety (SCCS) — opinions on cosmetic ingredients

Written and reviewed by Dr Ellene Papazis, dermatologist accredited in Portugal and Brazil. Consultations in Porto, Portugal.

Updated 25 July 2026.