What Causes Petechiae on the Roof of the Mouth? Petechiae are small purple, red, or brown spots on the skin. They usually appear on the arms, legs, stomach, and buttocks. A person might also find them inside their mouth or on eyelids. These pinpoint spots can be a sign of many different conditions. They can also appear as a reaction to certain medications. Though petechiae look like a rash, they’re actually caused by bleeding under the skin.