• Josep Orellana, science journalist

    Contact dermatitis: substances to avoid

    11 Nov Contact dermatitis: substances to avoid




    Clinical Key

    Contact dermatitis is one of the ten main reasons for primary care consultations. More than 3,000 substances may cause contact dermatitis on different people’s skins. Certain cosmetics, hair dyes and shampoos contain potentially irritating components. Identifying the causative agent is crucial.


    Contact dermatitis is an inflammatory reaction of the skin due to exposure to certain substances. Irritant contact dermatitis is when a product first produces a local toxic effect in the skin cells, whereas allergic contact dermatitis is when a substance causes an allergic reaction due to skin sensitization from repeated contact.


    The main symptoms are redness, dryness, swelling, itchiness, peeling and the formation of blisters. The most affected areas are usually the hands, neck, arms, face, legs and feet. Unlike hives, contact dermatitis may last days, weeks or even months.


    Who is affected?

    According to the World Allergy Association, contact dermatitis is responsible for 90% of workplace-associated skin disorders, linked as it is to occupations involving exposure to irritants or allergens.


    Although anyone may develop contact dermatitis, a family history increases the risk. Contact dermatitis mainly affects women, but young people are also especially vulnerable and up to 20% of infants may develop contact dermatitis due to nappy friction and urine.


    Nickel, enemy number one

    We daily come into contact with irritants or allergens that can potentially cause contact dermatitis:


    • Nickel: The main cause of contact dermatitis worldwide. Found in millions of products, such as buttons, zippers, jewellery, chrome-plated objects, white gold, etc.
    • Latex: Used in gloves, belts, bras, condoms, balloons and toys.
    • Cosmetic preservatives: In shampoos, lotions, nail polish, deodorants, etc. Notable preservatives are quaternium-15, the isothiazolinones and sodium lauryl sulfate.
    • Soaps: Powerful ammonia-containing detergents and bleach or potassium dichromate-based cleaning products. Irritant contact dermatitis is common in occupations that require frequent handwashing, for example, in the healthcare and food sectors.
    • Colouring agents: Used to dye textiles and leather.
    • Hair dyes: Contain paraphenylenediamine.

    • Drugs: Topical corticosteroids and antibiotics, such as neomycin and bacitracin.
    • Fragrances: A given fragrance may contain hundreds from among over 5,000 known odorants. Some of these (26) are allergenic and their concentration levels in cosmetics are governed by European legislation.

    The key is prevention

    Contact dermatitis is easily and effectively cured. The first thing to do is identify the cause and avoid contact with the product in the future.


    It is crucial to recall where you were and you were doing 24 to 48 hours before outbreak and identify what contact you had with soaps, detergents and other products.


    If you have a reaction to an irritant or allergen, wash the skin using mild soap and cold water. Apply calamine lotion or ointment to relieve the itching.


    It is very important not to scratch so as to avoid infection. It is also advisable to keep the skin properly hydrated with an hypoallergenic cream. If the swelling does not subside within a matter of days you should contact your dermatologist.