Diagnosis - Contact dermatitis

Your GP can usually diagnose contact dermatitis from your symptoms and the look of your skin.

Your GP will ask when your symptoms first appeared and what substances you've been in contact with.

Identifying allergens and irritants

If your GP diagnoses contact dermatitis, they'll try to identify the cause. If you can identify the allergens or irritants, you can try to avoid those substances. This can reduce the risk of having symptoms.

Your GP will look at your medical history and ask questions about your lifestyle and job. They may ask you if there's a history of dermatitis or eczema in your family.

Referral to a specialist

If you cannot identify the cause of your contact dermatitis, your GP may refer you to a dermatologist. A dermatologist is a doctor who specialises in treating skin conditions.

Your GP may also refer you to a dermatologist if you know the cause but your symptoms do not improve with treatment.

Testing for allergens

The best way to test for a reaction to allergens is by patch testing. During a patch test, tiny amounts of known allergens are applied to your skin.

The substances are put on your back using a kind of non-allergic tape. They may sometimes be put on your upper arms.

After 2 days, the patches are removed and your skin is assessed to check for any reactions.

Your skin will usually be examined again after another 2 days. This is because most allergic contact dermatitis reactions take this long to develop.

Testing for irritants

It's difficult to test if specific products irritate your skin. Testing for these is unreliable.

In some cases, a repeated open application test (ROAT) is useful. This is often used to test cosmetics. A ROAT involves putting the substance onto the same area of skin twice a day for 7 days, to see how your skin reacts.

This is a useful way for you to check your cosmetics at home for reactions.


Content supplied by the NHS and adapted for Ireland by the HSE

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

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