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Allergic Contact Dermatitis
Allergic contact dermatitis
or better known as “eczema” or “dermatitis” is a form of an excessive immune (allergic) response of skin to some matter that got in touch with the skin. Skin gets very itchy and red, sometimes with tiny blisters. It may weep and later on becomes scaly. If the itching is absent, then other causes should be considered. If allergic response continues for weeks, then skin becomes thicker. Skin lines become easy to see, similar to the appearance of the skin lines on the tips of elbows. If this thickening of the skin is present than health care providers call it lichenification. Usually allergic response of the skin is just at the area of skin contact with an allergen (matter that caused allergic response), but sometimes this reaction can occur in remote areas, which is called “autosensitization” or “id” reaction. Sometimes allergic reaction requires exposure to sun or ultraviolet radiation to become visible. This is called “photoallergic contact dermatitis”.
Atopic dermatitis has similar appearance to allergic contact dermatitis and is also called in general public as “eczema”, but it is usually widespread, it occurs more in children, especially in children who have problems with breathing such as asthma, bronchitis and seasonal allergies. Please click on the separate “atopic dermatitis” or “eczema” tab for more detailed information.
Allergic contact dermatitis does not occur on the first contact of the skin with an allergen, since it takes at least several weeks for our immune system to develop excessive immunity against the allergen. If you get in touch with the same allergen again, then it takes about 12-48 hours to show up on the skin in the form of itchy redness, small blisters, weeping and later on scaling.
A classic example and one of the most common causes of allergic contact dermatitis in the U.S. is poison ivy.
What should I do if I suspect that I have allergic contact dermatitis?
You should first think as what could have been the cause (i.e. to what chemicals or substances including foods your itchy skin got in touch) both at home and at your workplace. You can always do so-called “user test”. Any substance (but only the ones that are designed to stay on skin – various creams, lipsticks, makeups etc.) that you suspect is the cause of your dermatitis, you rub on to one of your inner forearms once daily for seven days without washing it off. For substances that are not designed to stay on the skin (e.g. shampoos, detergents, soaps etc.) you dilute with water and rub into the skin of one inner forearm and then wash it off in a few minutes mimicking the normal use. If you develop itching and redness then ta-da! – you have found the cause and you need to start avoiding it. You should see your health care provider, if you cannot find the cause, and if over-the-counter hydrocortisone 1% ointment (we prefer ointments over creams for dermatitis since ointments are simpler and with less inactive ingredients compared to creams) twice daily for 1-2 weeks did not help.
How will my health care provider help me?
If the information above did not help you, your health care provider may do some more investigation to help you figure out the cause of your rash, and can prescribe you with stronger ointments to speed up the healing. If you still have the rash then allergen patch testing should be done. A dermatologist usually does this test over the course of one week requiring 3 appointments. On day one (e.g. Monday), 36 or more different fingertip-sized patches containing substances that are known to be the most common causes of skin allergies are taped to your back. On day three (e.g. Wednesday), these patches are removed from your back and the first reading is done. On day five (e.g. Friday) the final reading is done. During this time you should not wet you back either by showering, bathing or by sweating. Sometimes even this testing cannot determine the exact cause of your allergies, since it is impossible to test for all the chemicals our skin gets exposed to in everyday life.
Other than avoiding possible allergens what is the treatment for my allergic contact dermatitis?
The mainstay treatment of the allergic contact dermatitis and other eczemas are corticosteroid ointments of various strengths. These ointments are sometimes several hundreds times stronger than over-the-counter hydrocortisone 1% ointment. Weaker corticosteroid ointments are used on the face, skin folds such as groin, armpits and genitalia, while the strongest are used on palms and soles. In our dermatology practice we very rarely use corticosteroid pills (e.g. prednisone or methylprednisolone dose packs). Although we have seen very severe cases of dermatitis, we have never needed to use any corticosteroid injections (“shots”) for any of our patients. Intensive use of mid-strength corticosteroid ointments such as triamcinolone acetonide 0.1% ointment twice daily, helped with limited use of the strongest corticosteroids such as clobetasol 0.05% ointment is enough in the vast majority of cases. Sometimes we use triamcinolone acetoinde ointment for so called “body wet wraps”. If used properly, these wraps usually clear even the most severe eczemas in a week or two. In addition we use diluted bleach baths (half a cup of regular bleach stirred into the half a bathtub of water) or CLn wash (shower gel with bleach: http://www.clnwash.com) 1-3 times weekly for 10-15 min to disinfect the skin. Afterwards you should rinse your skin well and apply any prescribed ointment while your skin is still wet. These bleach baths and shower gels are necessary, since various bacteria can colonize your skin, worsen eczema, and make it resistant to treatment. Sometimes antibiotic pills that you take by mouth are also necessary. Newer ointments and creams such as pimecrolimus (brand name: Elidel) and tacrolimus (brand name: Protopic) are sometimes used, if patients cannot tolerate, or if they have side effects of corticosteroids. We use them rarely in our practice.