A petechia (pl. petechiae) is a small (1 - 2 mm) red or purple spot on the skin or conjunctiva, caused by a minor bleed from broken capillaryblood vessels. The word is derived from Latin 'petigo', meaning 'scab' or 'eruption'.
Petechia refers to one of the three descriptive types of hematoma differentiated by size, the other two being ecchymosis and purpura. Ecchymosis is defined as hematomas larger than 1 centimetre and purpura as 1-5 millimetres.
The term is almost always used in the plural, since a single lesion is seldom noticed or significant.
Coughing, holding breath, vomiting, crying - The most common cause of petechiae is through physical trauma such as a hard bout of coughing, holding breath, vomiting, or crying, which can result in facial petechiae, especially around the eyes. Such instances are harmless and usually disappear within a few days.
Constriction, Asphyxiation - Petechiae may also occur when excessive pressure is applied to tissue (e.g., when a tourniquet is applied to an extremity or with excessive coughing or vomiting).
Sjögren's Syndrome - Petechial spots could occur due to vasculitis, an inflammation of the blood vessels. In such a case immediate treatment is needed to prevent permanent damage. Some malignancies can also cause petechiae to appear.
Petechiae on the face and conjunctiva (eyes) can be a sign of a death by asphyxiation, particularly when involving reduced venous return from the head (such as in strangulation). Petechiae are thought to result from an increase of pressure in the veins of the head and hypoxic damage to endothelia of blood vessels.
Petechiae can be used by police investigators in determining if strangulation has been part of an attack. The documentation of the presence of petechiae on a victim can help police investigators prove the case. Petechiae resulting from strangulation can be relatively tiny and light in color to very bright and pronounced. Petechiae may be seen on the face, in the whites of the eyes or on the inside of the eyelids.