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 an irritant. The irritant damages the outer layer of your skin, causing redness, itching, burning or stinging.
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 will be at increased risk of irritant contact dermatitis if you have atopic eczema, which is the most common form of eczema.
Common irritants include:
- detergents and soaps
- antiseptics and antibacterials
- perfumes and preservatives in toiletries or cosmetics
- oils used in machines
- chemicals, such as disinfectants
- acids and alkalis
- water, especially hard, chalky water or heavily chlorinated water
- some plants, such as clematis, hellebore and mustards
Irritant dermatitis at work
You may be more at risk of contact dermatitis if you work with irritants as part of your job or if your job involves a lot of wet work. If you do 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:
- cleaners and housekeepers
- food preparers, cooks and and caterers
- hairdressers and beauticians
- farm and fisheries workers
- engineers and construction workers
- healthcare professionals (including dentists and vets)
- printers and painters
Other contributing factors
If you already have contact dermatitis symptoms, they can be made worse by:
- friction (rubbing against the irritant)
- low humidity (dry air)
These are more of a risk if you have irritant contact dermatitis.
Allergic contact dermatitis
Allergic contact dermatitis occurs when you come into contact with an allergen which causes your immune system to react abnormally. Your immune system is the body’s natural defence system that usually protects your body against infection and illness. During an allergic reaction, the immune system can attack healthy cells and tissue as well. This is what causes your skin to be sore and inflamed.
The first time you come into contact with a type of allergen, your body becomes sensitised to it. It's only when you touch that substance again, that your skin reacts with an itchy red rash.
Common allergens that can cause allergic contact dermatitis include:
- metals, such as nickel or cobalt in jewellery
- cosmetics, such as fragrances, hair dye and nail varnish
- preservatives added to certain medicines (including medicated creams)
- rubber, including latex, a type of naturally occurring rubber
- textiles, particularly the dyes and resins that are contained in them
- strong adhesives (glue), such as epoxy resin adhesives
- some plants, such as chrysanthemums, daffodils, tulips and primula
- some topical medicines (medicines that are applied directly to the skin), such as topical corticosteroids and topical antibiotics