my boyfriend has developed purplish rash on his arms, it is very itchy and resembles blood blisters, I am having difficulty finding what may cause a rash like this, and I don't believe it to be poison oak, ivy, or sumac, and have never seen a bug bite that may cause such a reaction. Getting him to see a doctor is an excersize in futility most of the time, but I am slightly concerned at the appearance of the rash, topical over the counter and natural remedies do little to provide him with any relief