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Live Blog: Dermatitis: More than Scratching the Surface, with Matthew Zirwas, MD

In this live blog from the 12th Annual SDPA conference in Indianapolis, Dr. Matthew Zirwas spoke about dermatitis in its many forms including epi-dermatitis, allergic contact dermatitis, irritant contact dermatitis, and atopic dermatitis. Here are some of the highlights. 

Dr. Zirwas introduced the his lecture by saying that dermatitis should really have two types of classifications: epi-dermatitis and dermal dermatitis. Epi-dermatitis refers to the raised, red, superficial rashes for which topicals will work. Dermal dermatitis, on the other hand, will not respond to topicals.

When sharing his knowledge on contact dermatitis, Zirwas noted that when describing the allergen to patients, it is common for them to reflect on their last patch test from their allergist. Being allergic to dogs is different than being allergic to shampoo. In these cases, Zirwas explained that the allergens are small chemicals, not proteins. In other words, in dermatology you are dealing with man-made allergens. When you do patch test for allergens, Zirwas shared the tip to actually feel the skin. It’s a given when responses are large and bulbous, but other reactions could be missed if relying only on sight.

The most common allergic contact dermatitis, Dr. Zirwas shared, is poison ivy. To dispel the old wives tales, he clarified that poison ivy cannot be washed off after the first 15 minutes. After those 15 minutes, it is bound to the skin. It also cannot be spread after it is bound. For example: If it looks like the poisy ivy spread because of the exposure of each spot (an intense high-exposure rash on the forearm shows up before the little exposure-rash on the shoulder) then the poison ivy has not spread by itching but because of exposure and time.

Time and exposure have a lot to do with the resolution of contact dermatitis as well. The rate of improvement is proportional to the rate of exposure. The allergen is on the keratinocytes and it won’t go away until those keratinocytes shed. In relation to this, Dr. Zirwas warned to keep patients on the prednisone long enough that the allergen will be shed from the skin (recommended time is 3 weeks). The epidermis has to renew itself a few times before it goes away. It’s also good to let patients know that there is nothing that can keep them from reacting to the poison ivy once exposed. Moreover, if it is in, say, your gardening gloves, you will continue to get a rash on your hands until you get new gloves.

Image: Mike Jennings