Hair dyes: what the Anses alert reveals about substances to be monitored in 2026

A simple hair coloring may seem harmless. However, in April 2026, the French health agency Anses issued an alert after identifying 124 cases of adverse reactions linked to hair dyes. Behind this common beauty gesture lies a complex chemistry that has experts worried.

What hair color really contains

Permanent colorants account for 70-80% of the European market. These products rely on a precise mechanism: opening up the hair fiber to deposit long-lasting pigments. To achieve this, they use substances such as ammonia and hydrogen peroxide.

This mixture ensures stable color over time. However, it can also weaken the scalp and provoke reactions. So even a product that has been used for years can suddenly cause problems.

So-called “gentle” formulas are not totally harmless. Semi-permanent or temporary dyes also contain ingredients that can irritate the skin.

“PPD is one of the most powerful contact allergens in cosmetics.

Substances singled out by health authorities

Certain molecules are attracting the attention of experts. These include paraphenylenediamine, better known as PPD. Toluene-2,5-diamine sulfate and persulfates are also found in bleaching products.

These substances are not prohibited. However, they can trigger allergic reactions in some people. A publication in J. Asthma Allergy confirms the high allergenic potential of PPD.

Sometimes severe reactions, even after years of use

The cases analyzed by Anses between 2019 and 2025 reveal varied effects. Some users report itching or burning sensations. Others describe facial swelling or breathing difficulties.

The body can become progressively sensitive to certain substances. In fact, an allergy can develop even in people accustomed to dyes. This development is often invisible at first.

• Itchy scalp
• Localized burns
• Edema of the face or neck
• Extensive redness beyond the application area
• Breathing difficulties in the most severe cases

In the absence of sufficient allergological tests, it remains difficult to identify the substances responsible in each case. This uncertainty reinforces the need for vigilance in every application.

Why these allergies are difficult to anticipate

A person can use the same hair color for years without a reaction. Then, suddenly, an allergy occurs. The immune system gradually becomes sensitized to certain molecules.

Hair coloring can cause allergic contact dermatitis. These manifest as redness, itching or burning sensations on the scalp, face or neck.

Precautions to take before colouring your hair

In the light of these findings, the health authorities stress the importance of not trivializing the use of tinctures. A simple skin test, in the crease of the elbow for example, is recommended before each application. This step enables us to detect the beginnings of a reaction.

Compliance with instructions for use remains essential. Avoid reapplication if you have an allergic history. Keeping product information can also prove useful in the event of medical consultation.

In the event of a serious reaction, prompt treatment is essential. Today, a better understanding of what we apply to our hair is the best way to limit the risks associated with hair coloring.

From now on, women and men who use hair dyes, whether at home or in a salon, will benefit from being informed about the composition of these products. Vigilance doesn’t mean giving up on changing color, but rather adopting simple gestures to protect your health.

• hair coloring