Cosmetic ingredients that may cause contact dermatitis.

As previously mentioned, contact eczema can occur following the use of certain cosmetic products and does not require a specific genetic predisposition. There are numerous cosmetic products that can trigger this reaction.

• Lip cosmetic products (lipstick, lip gloss, lip balm, etc.) : lesions are observed on the lips and/or around the mouth.

• Haircare products (shampoo, hair dye, hairspray) : an allergy to these products manifests itself through lesions on the scalp. These lesions can extend to the face or back in the case of a shampoo, as the product runs during rinsing.

• Nail polishes : An allergy to nail polish can lead to lesions on the face, which we often touch. This is referred to as 'manuported eczema'.

• Fragrances : an allergy to fragrances can lead to lesions or redness, most commonly on the neck and wrists, where the fragrance is applied.

• Emollients : Depending on the cosmetic ingredients incorporated into face or body creams, the skin may become irritated upon contact and develop lesions.

• Photo-allergens : The combination of a cosmetic product containing an allergen and exposure to UV rays can sometimes induce a photo-allergy. Lesions and redness then appear on the body.

It is important to understand that an allergy caused by a cosmetic product is not an allergy to a type of product or to the products of a specific brand. In other words, if the use of makeup remover wipes from a certain brand triggers an allergic reaction in you, it does not mean that you are allergic to all makeup remover wipes or to all products of that brand. In fact, an allergy to a cosmetic product is caused by a substance contained within that product.

• The Perfume : Contact eczema following the use of a perfume is very common. Whether they are natural or synthetic, perfumes contain a large number of allergenic substances (alcohols, aldehydes, catechols, ketones, esters, phenyl esters, etc.).

  Fragrances are present in a vast number of cosmetic products and even constitute a significant selection criterion for consumers. Contact eczema following the use of perfume is very common. It manifests as itchy red lesions on the area where the perfume has been applied. Indeed, this can be explained by the significant presence of allergens in perfumes. Sometimes, natural fragrances are more allergenic than synthetic ones due to their high concentration of essential oils.

• A preservative : in cosmetic products, the use of preservatives is essential to prevent the proliferation of microorganisms, particularly in products containing water, a medium that promotes microbial growth. Just like fragrances, preservatives can be responsible for allergies. For instance, the methylisothiazolinone (MIT), a preservative that was widely used in cosmetic products, has been banned in leave-on products, as it is highly likely to cause contact dermatitis.

  Other preservatives are known to cause contact dermatitis: benzyl alcohol, dehydroacetic acid, or even sorbic acid. Moreover, certain essential oils can be used as preservatives due to their antimicrobial or antifungal properties, such as rosemary essential oil or tea tree essential oil. These can trigger an allergic reaction due to the allergenic molecules they contain (limonene, citronellol, geraniol, etc.).

• A pigment : the paraphenylenediamine (PPD) is a pigment used in hair dyes that causes itchy lesions on the scalp after dyeing.

  The henna used for temporary skin tattoos is often mixed with PPD, which carries a significant risk of contact dermatitis.

Please note : some natural ingredients used in cosmetics can cause strong allergic reactions. This is particularly the case for the propolis and also the arnica.

In the event of contact eczema following the use of a cosmetic product, the first step is to cease using the offending product. Once the product is removed, the lesions of contact eczema progress towards healing in 10 to 15 days. During the healing period, the use of emollient balm and a corticosteroid-based anti-inflammatory cream helps to reduce the lesions of eczema.