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 visible symptom of a serious illness:

• Petechiae (say "pet-TEA-key-eye") are tiny, flat red or purple spots in the skin or the lining of the mouth caused by abnormal bleeding from small blood vessels that have broken close to the skin or the surface of a mucous membrane. Petechiae may spread over a large area of the body within a few hours. Petechiae spots range from pinpoint-size to BB-size and do not itch or cause pain. They are different than tiny, flat red spots or birthmarks (hemangiomas) that are present all the time. Petechiae do not turn white when you press on them. Petechiae that develop quickly over a few hours may mean that you have a serious infection or a not enough platelets (part of the body's defense against bleeding)—this requires medical treatment right away.
• Purpura is sudden, severe bruising that may be localized, regional, or widespread and that occurs without an injury. People who develop purpura often have signs of illness, such as a fever, weakness, fatigue, or a vague sense of being ill (malaise). The bruising caused by purpura is different from the isolated bruises a person often gets after bumping into an object or falling. A bleeding or clotting disorder is the most common cause of purpura. Purpura that comes on quickly over a short period (a few hours) may mean you have a serious infection that requires medical treatment right away.

Nonprescription and prescription medicines may also cause abnormal bruising or bleeding. If you have noticed abnormal bleeding after starting a new medicine, particularly if you take several medicines, call your health professional.