What does contact allergy mean?
As you would expect, this is an allergy that develops from contact with something -- for example, being allergic to a soap or lotion, dyes, metals, rubber, etc. -- a very familiar type of contact allergy is the itchy skin reaction from touching poison ivy.
What does contact allergy look like?
Contact dermatitis usually is localized to one or a few areas of the body, is red and itchy, and could look like patches of scaly dry skin, crops of little bumps, or in severe cases the skin may blister, break and ooze.
Where do I start if I think I might have a contact allergy?
Looking for the cause is paramount. Become a detective. Think about all the things that touch your skin in the involved areas -- soaps, lotions, shampoos, items on clothing (elastic bands or snaps, for example), jewelry, leather boots, etc. Is there something that you do in the course of your day that may be keeping this rash going?
But I've been using that shampoo for years and the rash only started last month. That can't be it, right?
Wrong. Actually, most contact allergies develop only after repeated exposure over time. Sometimes even after months or years of using a product. The skin cells take some time to be sensitized.
So I should be able to tell by just thinking about what I am touching?
Sometimes it is very obvious what the cause is, once you start thinking about what touches the area of the rash. Other times, it can be confusing, for a couple of reasons:
- delayed reaction: generally there is a 2-5 day delay in developing the rash after exposure to the offending substance
- triggering of rash by exposure to a different area of the skin: Once the skin of one area of the body becomes sensitized, exposure to the offending substance even in a different area of the body can trigger a flare at the original site. For example, itchy earlobes from allergy to nickel jewelry may flare up even if you don't wear earrings anymore, but put on a metal watchband.
What if I can't figure it out on my own? Is there some kind of test to help identify the cause?
Yes, that test is called "patch testing". It is different from the skin testing we do to look for nasal allergy triggers such as pollens or dust, and different from standard food allergy testing. This contact allergy test takes a few days to develop on the skin, after common substances that often cause skin sensitization are placed on your back under special tape, and left there for 48 hours. We can also test your own hair or skin care products to quickly find the ones that are causing trouble.