What is contact dermatitis?
Contact dermatitis is inflammation of the skin caused by direct contact with a substance. There are two main types: irritant contact dermatitis, which is far more common and results from repeated exposure to mildly irritating substances (soaps, detergents, water) damaging the skin's barrier; and allergic contact dermatitis, a true immune reaction to a specific allergen, which can develop even after years of previously uneventful contact with that substance.
Common triggers
- Irritant type: frequent hand-washing, detergents, soaps, solvents, and prolonged wet work.
- Allergic type: nickel (jewellery, belt buckles), fragrances, preservatives in cosmetics, certain plants, rubber/latex, and some topical medications.
- Occupational exposure is a common factor for both types — hairdressers, healthcare workers and cleaners are frequently affected.
Signs and symptoms
- Redness, itching, and dryness or scaling at the site of contact.
- Sometimes blistering, particularly in allergic contact dermatitis.
- A clear pattern matching the area of contact — for example, a band of rash under a ring or watch.
- Can become chronic with repeated exposure, leading to thickened, cracked skin.
Diagnosis
A careful history of exposures — at home, work, and in personal care products — is often the key to identifying the trigger. For suspected allergic contact dermatitis where the cause isn't obvious, we may refer for patch testing, a specialised test that identifies specific allergens.
Treatment options
Avoiding the trigger
The most important step once an irritant or allergen is identified.
Emollients
Regular use of a fragrance-free moisturiser to repair and protect the skin barrier.
Topical corticosteroids
To settle active inflammation during flares, used as directed by your doctor.
Patch testing referral
For persistent or unclear allergic contact dermatitis, to pinpoint the specific allergen.
Prevention
- Wear protective gloves for wet work, cleaning, or handling known irritants.
- Moisturise regularly, especially after hand-washing.
- Choose fragrance-free, hypoallergenic personal care products if you have sensitive skin.
- Once an allergen is identified, check ingredient lists carefully to avoid it in future.
Frequently asked questions
What's the difference between irritant and allergic contact dermatitis?
Irritant contact dermatitis results from direct damage to the skin barrier by a substance — it can affect anyone with enough exposure. Allergic contact dermatitis is a true immune reaction to a specific allergen, and only occurs in people who have become sensitised to that substance.
Can I suddenly become allergic to something I've used for years?
Yes — allergic contact dermatitis can develop after years of previously fine exposure, once your immune system becomes sensitised to a substance. This is different from irritant dermatitis, which is more directly related to how harsh or frequent the exposure is.
How is the specific allergen identified?
Through patch testing — small amounts of common allergens are applied to the skin (usually on the back) under adhesive patches and checked over several days for a reaction. It's a specialised test usually arranged through a dermatologist.