Contact dermatitis - Causes of contact dermatitis

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

This can be either:

an irritant – a substance that damages the skin
an allergen – a substance that can cause the body to react abnormally

Irritant contact dermatitis

Irritant contact dermatitis occurs when your skin comes into direct contact with a substance that damages the outer layer of your skin, causing redness, itching, and a burning or stinging sensation.

Irritant contact dermatitis may be caused by frequent exposure to a weak irritant, such as soap or detergent. It may also develop if you've been in contact with a stronger irritant for a short while.

You are at an increased risk of irritant contact dermatitis if you also have atopic eczema, which is the most common form of eczema.

Common irritants include:

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

If you already have irritant contact dermatitis symptoms, they can be made worse by heat, cold, friction (rubbing against the irritant) and low humidity (dry air).

Exposure at work

You may be more at risk of irritant contact dermatitis if you work with irritants as part of your job, or if your job involves a lot of wet work. If you develop the condition because of a substance you work with, it may be referred to as occupational irritant dermatitis.

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

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

Allergic contact dermatitis

Allergic contact dermatitis occurs when you come into contact with a substance that causes your immune system to react abnormally.

Your immune system is the body’s natural defence system, which usually protects your body against infection and illness. During an allergic reaction, the immune system attacks healthy cells and tissue as well. This is what causes your skin to become sore and inflamed.

The first time you come into contact with an allergen, your body becomes sensitised to it, but does not react to it. It's only when you are exposed to the substance again that your skin reacts with an itchy red rash.

Allergens that commonly 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 topical medicines (medicines that are applied directly to the skin) – including topical corticosteroids, in rare cases
rubber – including latex, a type of naturally occurring rubber
textiles – particularly the dyes and resins that are contained in them
strong glues – such as epoxy resin adhesives
some plants – such as chrysanthemums, sunflowers, daffodils, tulips and primula