Rashes are usually not the first symptom to appear when a serious disease is present. Other symptoms will commonly occur before the rash. Early symptoms of a serious disease may include fever, a general feeling of illness, or a decreased level of activity.
There are two types of rashes that may be the first noticeable symptom of a serious illness:
Nonprescription and prescription medications may also cause abnormal bruising or bleeding. If you have noticed abnormal bleeding after starting a new medication, particularly if you take several medications, call your health professional.
WebMD Medical Reference from Healthwise