Petechiae are tiny, flat dots on the skin that are purple, red, or brown, each about the size of a pinpoint. They measure less than 4 millimeters in diameter, roughly the size of the tip of a ballpoint pen. They don’t itch, don’t raise above the skin’s surface, and won’t fade when you press on them.
Size, Color, and Shape
Each petechial spot is a small, round, flat dot. Fresh petechiae tend to be bright red or dark red. Over time, they shift toward purple or brown as the trapped blood beneath the skin breaks down. This color change can take a few weeks and may pass through shades of orange, blue, and green before fading entirely, similar to the way a bruise evolves.
Petechiae almost always appear in clusters rather than as a single isolated dot. A group of them can look like a fine spray of reddish-purple speckles across the skin. Because they sit flat against the surface, running your finger over them won’t reveal any bump or texture change. They don’t hurt or itch on their own.
How to Tell Them Apart From Other Spots
The defining feature of petechiae is that they don’t blanch, meaning they don’t temporarily disappear when you press on them. Most common rashes, like hives or viral rashes in children, turn white (or match the surrounding skin tone) under pressure because the redness comes from dilated blood vessels that empty when compressed. Petechiae come from blood that has already leaked out of the vessels and is sitting in the skin tissue, so pressure has no effect on their color.
A simple way to check this at home is the glass test: press a clear drinking glass firmly against the spots. If the dots stay visible through the glass, they are non-blanching, which is the hallmark of petechiae and related bleeding under the skin.
Size is the other key distinction. Spots under 4 mm are petechiae. Spots between 4 and 10 mm are called purpura. Anything larger than 1 centimeter is classified as ecchymosis, which is essentially a bruise. All three involve blood leaking under the skin, but petechiae are the smallest of the group.
Where They Typically Appear
Petechiae can show up anywhere on the body, but certain locations are more common depending on the cause. When they result from physical strain (heavy coughing, vomiting, or even intense crying), they often cluster on the face, especially around the eyes, and on the neck and upper chest. This happens because the pressure from straining forces blood into the tiny capillaries of the head and face, sometimes rupturing them.
Petechiae caused by other factors, like low platelet counts or infections, tend to appear on the lower legs, ankles, and feet first, since gravity puts extra pressure on blood vessels in those areas. They can also appear inside the mouth, on the inner eyelids, and on the inner surfaces of the lips. These mucosal locations are particularly useful for spotting petechiae on people with darker skin tones, where the dots can be harder to see on the arms or legs.
What Causes Them
Petechiae form when capillaries, the smallest blood vessels in your body, break and leak tiny amounts of blood into the surrounding skin. The leaked blood gets trapped just beneath the surface, creating each visible dot.
Many causes are completely harmless. Physical straining is one of the most common triggers. A bout of forceful vomiting, a prolonged coughing fit, heavy weightlifting, or even straining during childbirth can produce a crop of petechiae on the face and chest that resolves on its own within a few days to a couple of weeks. Tight clothing, tourniquets during blood draws, or even vigorous scratching can cause localized petechiae in the affected area.
Other causes are more significant. Low platelet counts (from conditions that affect how your blood clots), certain infections, reactions to medications, and some autoimmune conditions can all trigger widespread petechiae. In these cases, the spots tend to appear in larger numbers, spread to multiple body areas, and may come alongside other symptoms like fatigue, fever, or easy bruising elsewhere.
Petechiae on Darker Skin Tones
On lighter skin, petechiae stand out clearly as red or purple dots against a pale background. On medium to dark skin tones, the contrast is lower, and the spots may appear as dark brown or nearly black dots that blend more with surrounding skin. They can be easy to miss, especially when scattered lightly across the legs or arms.
Checking areas where the skin is naturally thinner or lighter can help. The inside of the lower eyelids, the roof of the mouth, the inner lips, and the palms of the hands are all places where petechiae remain visible regardless of skin tone. If you suspect petechiae but can’t see them clearly on the arms or legs, these mucosal areas are worth examining.
How Long They Last
Petechiae from a one-time mechanical cause (like vomiting) typically fade over one to three weeks. As the leaked blood breaks down, the spots shift from red or purple through brownish and sometimes greenish hues before disappearing completely. They don’t leave scars.
If new petechiae keep appearing as old ones fade, that suggests an ongoing process rather than a single event. Rapidly spreading petechiae, spots that appear alongside a high fever, or petechiae accompanied by unusual bleeding from the gums, nose, or in the urine all point to something that needs prompt medical evaluation. A sudden, widespread crop of non-blanching spots that develops over hours, particularly in a child with fever, is treated as urgent.