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Skin Care and Diseases

Mysterious Rash



My mother, who lives on a working farm, noticed a red and very itchy rash recently all along her right arm that has spread to the upper part of her body on the right side. It got a little better after a few days of prednisone but now has spread to the left side of her chest and left arm. While it seemed like it might be poison ivy at the very first (possible blister on her arm), she is familiar with poison ivy and once it started to spread it didn’t look like a poison ivy rash at all – just red and itchy. A clue might be a large guard dog that loves to come to her right side to be petted and sleeps in the house at night. While the dog is big, she is still a puppy at 11 months old and pushy (eager!) to get attention. Because of her size and long white (shedding) hair there is a lot of contact with hands and arms. During the day she runs free and there many plants and other weeds, including poison ivy, in the area.


A dermatologist can help differentiate poison ivy dermatitis (resin transferred from the dog) from a primary blistering process of the skin like bullous pemphigoid or even a reaction to cheyletiella mites present on the dog.

If you see a blister, photograph it for the dermatologist to inspect; true blisters filled with fluid can help to narrow the list of diagnostic possibilities, but it is often difficult for patients to describe what they mean by a blister as opposed to other forms of rash.

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Response by:

Susan T Nedorost, MD Susan T Nedorost, MD
Associate Professor of Dermatology
School of Medicine
Case Western Reserve University