I am seeing a dermatologist and we are trying to determine what is causing (an allergic reaction) a sever rash that appears on my lower back (lumber section) and going down the back of my legs. We are changing some of my blood pressure meds and have temporarily discontinued atorvastatin for cholerterol. Looking to the past, taking otc robitussin, vicks and unisom, all containing doxylamine could be a factor. I think I have ruled out fish. Some of the rash is the size of a quarter and has a (?) center (?) It is sometimes itchy, very red and almost completely covers the lumbar portion of my back and this time I got it, it is also on the lower back of my legs, but really not as severe.