Irritant reactions can occur after a single exposure or after repeated exposures over time, whereas it takes multiple exposures to the same chemical to develop an allergy. People who work in certain professions have a higher risk of developing contact dermatitis. You might repeatedly encounter irritating chemicals or allergens in these professions:
- Construction workers.
- Food handlers.
- Healthcare providers.
- Janitors and plumbers.
Tink poison ivy or poison oak.
The two main types of contact dermatitis are:
Allergic contact dermatitis: Your body has an allergic reaction to a substance (allergen) that it doesn’t like. Common allergens include jewelry metals (like nickel), cosmetic products, fragrances and preservatives. It can take several days after exposure for an itchy, red rash to develop.
Irritant contact dermatitis: This painful rash tends to come on quickly in response to an irritating substance. Common irritants include detergents, soap, cleaners and acid.
Clinical examination can reveal clues to the underlying diagnosis of irritant or allergic contact dermatitis. A careful history can uncover clues as to the offending agent.
With either type of contact dermatitis, you can avoid the substance for a while to see if the rash goes away. If avoidance is not possible or not sustainable, further diagnostic testing may be indicated.
For suspected cases of allergic contact dermatitis, a series of tests called patch testing can identify the underlying cause of allergic contact dermatitis.
With a patch test, you wear adhesive patches on your skin. The patches contain chemicals known to commonly trigger allergic reactions. After 48 hours, your healthcare provider checks your skin for reactions. You’ll see your provider again in another 48-96 hours for one last skin check.
There isn’t a test for irritant contact dermatitis. Your healthcare provider may be able to determine what’s causing the rash based on the types of irritants or chemicals you’re exposed to regularly.