The most common drugs to cause skin rashes are antibiotics, particularly the commonly used – tetracyclines and sulfur drugs.  Other medications commonly associated with skin rashes are diuretics (fluid pills), blood pressure medications, and oral hypoglycemic agents for diabetes, although the likelihood is low in an individual patient, dermatologists see these rashes more commonly because these drugs are frequently used and there are large number of hypertensive and diabetic patients.  A trial of stopping the offending medication in consultation with the prescribing physician is in order.