Contact Dermatitis - Managing Your Allergies: Allergies
Content provided by the Faculty of the Harvard Medical School
Contact dermatitis
As its name implies, contact dermatitis occurs after a person’s skin comes in contact with the offending substance. Poison ivy and other plants of the genus Rhus are classic examples of allergens that can provoke allergic contact dermatitis. Most people are familiar with the itchy, red blisters that can follow a delightful walk in the woods. The poison ivy response works a little differently from many allergies because it is a T cell–mediated, not an IgE-mediated, response. Contact dermatitis can also flare up suddenly after you’ve been around a substance for some time with no problem — for instance, nail polish.
There’s another category of contact dermatitis called irritant contact dermatitis. This is not an allergic reaction, but the symptoms are similar. In irritant contact dermatitis, there is usually some process of cumulative hypersensitivity whereby you’re fine around a substance until the day you’re not. One example is the skin reaction people get from constant use of harsh detergents or solvents.
The list of substances that can trigger allergic or irritant contact dermatitis is quite long. Moreover, you may be bothered by substances that aren’t on the list.
Atopic and contact dermatitis triggers | |
| Atopic dermatitis (eczema) |
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| Allergic contact dermatitis |
*These can become a problem in the presence of sunlight |
| Irritant contact dermatitis |
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Treating contact dermatitis
Patch testing can help reveal the cause of the allergy or irritation if it is not readily apparent. Your first step in treatment is to wash the area thoroughly to remove any trace of the substance causing the reaction. Avoiding the trigger is the next step. Further treatment may not be necessary once the irritating substance is eliminated.
In some cases, your doctor may recommend topical steroid ointment to reduce inflammation; in severe cases, oral steroids may be necessary. These are generally tapered off gradually over about 12 days to prevent recurrence of the rash. Wet dressings and soothing lotions may help reduce itching and other symptoms. Keep an eye on the area for signs of infection.
Contact dermatitis usually clears up in about two to three weeks so long as you avoid further contact with the substance that caused it.
| Last updated: | August 21, 2006 |
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| Reviewed By: | Faculty of Harvard Medical School |
Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.
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