Petechiae are pinpoint-sized reddish spots, resembling a rash, that appear just under the skin or a mucous membrane when capillaries have ruptured and some superficial bleeding into the skin has happened. Capillaries are tiny blood vessels that connect arterioles, which are the smallest parts of an artery, to venules, which are the smallest parts of a vein. If a capillary breaks, it will begin to bleed, and the blood will leak into the skin or a mucous membrane, such as the mouth, which then causes the skin to become discolored. The main cause of petechiae is either simply aging skin or some type of local physical injury or trauma to the body, such as a particularly hard bout of crying, fits of violent coughing or forceful and prolonged vomiting. Petechiae that are caused by aging skin or physical injury will commonly show up on areas of the face, particularly around the eyes, and are regarded as generally harmless, usually going away in just a few days.
Spots of petechiae have a tendency to appear in clusters. Second to the facial area, petechiae might cluster on areas of the body where a lot of pressure is applied to the veins by blood circulation, such as the lower legs, ankles and feet. Petechiae can appear elsewhere on the body, however, even on the abdomen.
These tiny spots are less than 0.12 inches (3 mm) in diameter and are red in color at first because they contain red blood. They change to blue or purple as they age and, in many cases, they eventually disappear. Although facial petechiae are the most common, these red spots can actually appear anywhere on the body and can be caused by conditions other than injury or aging.
Different types of drugs might also be a cause of petechiae. Certain pain relievers, such as acetaminophen, aspirin and naproxen, might cause petechiae to appear. Taking certain drugs or medicines, such as steroids, some anti-platelet medications, anticoagulants or chemotherapy agents, might also be a cause of petechiae. An allergic reaction of any type, whether to a drug or a substance such as dust, can cause petechiae to develop.
Some serious illnesses and conditions might also be a cause of petechiae. Severe viral infections, leukemia, diseases that affect the blood clotting mechanisms and autoimmune conditions can cause petechiae as well. An individual who notices petechiae that persist on his or her body might consider consulting a dermatologist to determine the cause.