Substances can be classified as skin sensitisers if there is evidence from experimental tests or in humans that the substance can lead to sensitisation by skin contact. 

From information in the Classification and Labelling Inventory, there are over 14 000 substances on the EU market with some indication of a skin sensitising concern. These include, for example, chromium VI, nickel and cobalt compounds, and formaldehyde.  

These chemicals have many purposes and can be found in products for a variety of reasons. They may fulfil a specific function, such as the dyes found in textiles or in consumer cleaning products. Other chemicals may only be present unintentionally in low concentrations because they are impurities of raw materials or are used in the manufacturing process. 

The development of skin sensitisation starts when an allergenic substance activates the immune system. The first contact with an allergenic substance does not usually cause visible symptoms. However, re-exposure to the same substance can make the allergy manifest itself after a person comes into contact with the substance – called allergic contact dermatitis. 

So, if repeated over time, skin sensitisation is a health effect that can lead to a lifelong sensitivity to a specific allergen, and people who are sensitised must avoid exposure to the allergen for the rest of their life if they wish to avoid the symptoms.

Skin sensitisation is irreversible and cannot be cured, but symptoms can diminish if exposure is avoided. Moreover, contact to similar substances later on may cause allergic reactions even if that substance was not the one causing the original allergic reaction - this is known as cross-reactivity. 

It is difficult to avoid exposure to skin sensitising substances such as those that occur in textile and leather articles. This may be particularly problematic if sensitised individuals are unaware of which allergen they are reacting to.   

ECHA and Member States identify skin sensitisers based on registration data collected from industry under REACH. This data, together with information from several other sources, is screened and when a new potential substance of concern is identified, suitable regulatory risk management measures can be put in place.

For example, where substances are known to cause skin allergies, the EU may decide that they should be subject to harmonised classification and labelling or that their use should be restricted to protect citizens.

Classification, Labelling and Packaging (CLP) Regulation

There are a little over 1 000 chemicals that have a harmonised classification as skin sensitisers under the CLP Regulation. Companies that supply any substance onto the EU market with a harmonised classification, have to classify and label the substance – as well as any mixtures containing that substance – in the same way to ensure a high level of protection for people.

The harmonised classification entails legal requirements, such as labelling to inform users of substances and mixtures about their safe use. The labelling requirement, however, does not cover articles such as clothing, bedlinen or footwear.

Harmonised classification may help to determine what other risk management measures should be applied. It can, for example, form the basis to define which substances should be covered by a potential restriction.

REACH restrictions

The use of some skin sensitisers is already restricted under REACH.

Chromium VI, which was used in leather articles such as shoes, gloves and handbags, has been restricted since May 2015. It was estimated that this restriction could prevent 11 000 new skin allergy cases every year following its introduction while saving more than €350 million in reduced sick leave and medical costs. Use of chromium VI is also limited in cement and cement-containing mixtures, which cannot contain more than 2 mg/kg of the substance. This is to protect workers from being exposed to unhealthy levels of chromium.

Nickel has been the main cause of skin allergies in Europe for a long time. It has been restricted in articles that are in long-term contact with the skin, such as in earrings, necklaces, wristwatches and zippers in garments, since 2005.

The use of dimethyl fumarate (DMF), an anti-mould chemical that was commonly used in sachets accompanying consumer articles, such as shoes and sofas, has been restricted in the EU since 2012.

In 2017, ECHA, Denmark, Italy and Norway proposed to restrict more than 4 000 hazardous substances, including those classified as skin sensitising substances, used in tattoo inks and permanent make-up. 68 % of people with tattoos have reported skin problems with 6 % reporting persistent skin symptoms. At the end of 2020, the European Commission adopted the restriction and it started applying in the EU/EEU after 4 January 2022. This restriction aims to make tattooing and permanent make-up safer.   

In addition, the French and Swedish authorities have proposed a wide restriction on skin sensitising chemicals in textile, leather, synthetic leather, hide and fur articles. If adopted by the European Commission, this proposal would limit the use of over 1 000 skin sensitising chemicals (all those with a harmonised classification as well as some ‘disperse’ dyes considered to have skin sensitising properties) in clothing, footwear and other articles that come into contact with the skin, such as bed linen or upholstered furniture. As a result, many new allergies will be prevented while also relieving the symptoms of many of those who are already sensitised. This could save European society at least €708 million a year in reduced healthcare costs, productivity and welfare losses. ECHA’s scientific committees have provided their opinions on the proposal and support the restriction. The European Commission, together with the EU Member States, will decide on the proposal.