Causes - Contact dermatitis

Contact dermatitis happens when your skin reacts to a particular substance.

This can be:

• an irritant – a substance that damages the outer layer of skin
• an allergen – a substance that causes your immune system to react in a way that affects the skin

Irritant contact dermatitis

Irritant contact dermatitis can appear after you have contact with an irritant. This can be regular contact with a weak irritant or short contact with a strong irritant. Weak irritants are substances such as soap or detergent.

You have a higher risk of irritant contact dermatitis if you have atopic eczema. Atopic eczema is the most common form of eczema.

Common irritants include:

• soaps and detergents
• antiseptics, antibacterials and disinfectants
• perfumes and preservatives in toiletries or cosmetics
• solvents, oils used in machines, acids and alkalis
• cement, powders, dust and soil
• water and especially hard, chalky water or very chlorinated water
• many plants such as Ranunculus, spurge, Boraginaceae and mustards

Heat, cold, dry air and rubbing against the irritant can make your symptoms worse.

Contact with irritants at work

You may be more at risk of irritant contact dermatitis if you work with irritants in your job. You are also at risk if you work with water a lot.

If you have dermatitis because of an irritant at work, the condition may be called occupational irritant dermatitis.

This type of dermatitis is more common in certain occupations, including:

• agricultural and construction workers
• beauticians and hairdressers
• chemical workers and cleaners
• cooks and caterers
• metal and electronics workers
• health and social care workers
• machine operators, mechanics and vehicle assemblers

Allergic contact dermatitis

The first time you're in contact with an allergen, your body becomes sensitised to it. But your body does not react to the substance straight away. When you're in contact with the substance again, your immune system reacts. This causes your skin to become red and itchy.

Allergens that can cause allergic contact dermatitis include:

• cosmetic ingredients such as preservatives, fragrances, hair dye and nail varnish hardeners
• metals such as nickel or cobalt in jewellery
• some medicines that you apply to the skin, including topical corticosteroids in rare cases
• rubber or latex
• textiles and the dyes and resins that are in them
• strong glues such as epoxy resin adhesives
• some plants such as chrysanthemums, sunflowers, daffodils, tulips and primula