Hi and thanks for the query, Common causes of rapidly evolving rash could include viral disease, fungal disease or an allergic reaction. A clinical evaluation is very important to make a proper diagnosis. It would necessary to distinguish pain from itches. depending on the distribution of the rash, especially if it follows a specific pattern, exclusion of a chronic herpes virus infection coud be important. Zona is a probable diagnosis. exclusion of immune suppression fro HIV or diabetes or cancer could be necessary in this case. It is not excluded the the drug you take could be implicated. Relating the onset of these symptoms to the timing of the drugs could aid in discarding or confirming this possibility. I suggest you consult a dermatologist for a proper clinical review. Thanks and kind regards, Bain LE, MD.