Why do i suddenly have petechiae. i only had it once before 4 months ago. i thought it was an allergic reaction to something.

Petechiae: Petechiae are small red to purple spots on the skin caused by broken blood vessels. They are commonly seen in patients with low platelet counts or those with physical skin trauma. They can be seen in vasculitis (blood vessel inflammation) that can be part of a drug reaction or from an infection. The usual ige mediated allergies cause hives and not petechiae.