Petechiae are tiny, flat spots that appear on your skin when blood leaks from damaged capillaries just beneath the surface. Each spot measures less than 4 millimeters in diameter, roughly the size of a pinpoint or the tip of a ballpoint pen. They’re typically red, purple, or dark brown depending on your skin tone, and unlike most rashes, they don’t fade when you press on them. Petechiae can show up anywhere on the body but are most common on the face, neck, chest, and legs.
What Petechiae Look Like
Petechiae are flat to the touch. You won’t feel a bump or raised edge if you run your finger over them. They tend to appear in clusters rather than as isolated spots, which is why people often describe them as a “rash” even though each individual mark is extremely small. On lighter skin, they look bright red or reddish-purple. On darker skin tones, they can appear dark brown or even look like tiny bruises.
The key feature that sets petechiae apart from other rashes is that they don’t blanch. Most red rashes temporarily disappear when you press on them because you’re pushing blood out of dilated vessels. Petechiae don’t fade because the blood has already escaped the vessels and is sitting in the surrounding tissue. You can check this yourself with what’s called the glass test: press the side of a clear drinking glass against the spots. If they stay visible through the glass, they’re non-blanching, which confirms they’re petechiae rather than a typical inflammatory rash.
How Petechiae Differ From Purpura and Bruises
Petechiae, purpura, and bruises (ecchymosis) are all caused by the same basic problem: blood leaking out of vessels into the skin. The difference is size. Petechiae are less than 4 mm across. Purpura spots measure between 4 and 10 mm. Anything larger than 1 centimeter is classified as ecchymosis, which is essentially a bruise. If you’re seeing a mix of these sizes together, that pattern can help your doctor narrow down the cause.
Common Harmless Causes
Many cases of petechiae have a straightforward, non-serious explanation. Physical straining is one of the most common triggers. When pressure builds in tiny blood vessels near the skin’s surface, some of them rupture. This can happen during a bad bout of vomiting, a prolonged coughing fit, heavy weightlifting, or even childbirth. In these cases, the spots typically show up on the face, neck, and upper chest, which is where the pressure is greatest. They usually fade on their own within a few days without any treatment.
Other everyday triggers include tight clothing or tourniquets that put sustained pressure on the skin, sunburn, and minor injuries. Some people notice petechiae after crying hard or straining during a bowel movement. If the spots appear in a localized area and you can connect them to a clear physical cause, they’re generally nothing to worry about.
Serious Conditions Linked to Petechiae
When petechiae appear without an obvious physical trigger, spread across large areas of the body, or show up alongside other symptoms like fever, fatigue, or feeling generally unwell, they can signal something more serious. The underlying issue usually falls into one of three categories: low platelets, infection, or blood vessel inflammation.
Low Platelet Count
Platelets are the blood cells responsible for clotting. When your platelet count drops low enough, blood seeps through vessel walls more easily and you can’t form clots to stop the leaking. Petechiae typically start appearing when platelet counts fall into the range of 20,000 to 50,000 per microliter, well below the normal range of 150,000 to 400,000. At those levels, you might also notice that you bruise easily, bleed longer from small cuts, or have bleeding gums.
A low platelet count, called thrombocytopenia, has many possible causes. Your body might not be producing enough platelets (bone marrow problems, leukemia, certain vitamin deficiencies), or it might be destroying them faster than normal (autoimmune conditions, certain infections). Some medications are known culprits as well.
Infections
Both viral and bacterial infections can cause petechiae. Viral infections are the more common trigger, especially in children, and they typically resolve as the illness clears. Bacterial infections are the bigger concern. Meningococcal meningitis, a life-threatening bacterial infection of the membranes surrounding the brain, is famously associated with a rapidly spreading petechial rash. This rash can progress quickly from small dots to larger purplish patches over hours. If petechiae appear alongside a high fever, stiff neck, confusion, or a rash that’s spreading fast, that combination requires emergency medical attention.
Blood Vessel Inflammation
Conditions that inflame or damage blood vessel walls, known as vasculitis, can also produce petechiae. In these cases, the vessels themselves become fragile and leak. Autoimmune diseases like lupus and rheumatoid arthritis sometimes cause this type of vessel damage.
Medications That Can Cause Petechiae
Several common medications can lower your platelet count enough to trigger petechiae. Blood thinners, particularly heparin, are the most well-known cause of drug-related platelet drops. Chemotherapy drugs and the seizure medication valproic acid can also suppress platelet production directly.
Beyond those, a surprising number of everyday medications have been linked to low platelets:
- NSAIDs (ibuprofen, naproxen)
- Certain antibiotics (penicillin, sulfonamides, linezolid)
- Statins (cholesterol-lowering drugs)
- Quinine (found in tonic water and some malaria medications)
- Furosemide (a common diuretic)
If you notice new petechiae after starting a medication, that timing is worth mentioning to your doctor. Drug-induced platelet drops are usually reversible once the medication is stopped or changed.
How Doctors Find the Cause
The first thing a doctor will want to know is context: when the spots appeared, whether you’ve been sick, what medications you take, and whether you have any other symptoms. A physical exam helps determine whether the petechiae are localized (suggesting a physical cause) or widespread (suggesting a systemic problem).
A complete blood count is almost always the first lab test ordered. This measures your platelet levels and can reveal signs of infection or blood cancers. If platelets are low, additional tests help determine whether the problem is with production (bone marrow issues) or destruction (immune system attacking platelets, infection consuming them). Depending on the suspected cause, your doctor might also order tests for clotting function, kidney and liver health, or specific infections.
The glass test you can do at home is a useful first step, but it’s a screening tool, not a diagnosis. It confirms that the spots are non-blanching, which tells you blood has leaked into the tissue. It doesn’t tell you why.
Petechiae in Children
Petechiae are common in kids and often appear after forceful coughing or vomiting during a stomach bug. In those situations, the spots are usually limited to the face and upper body and resolve quickly. Viral illnesses are another frequent cause in children, and the petechiae clear up as the child recovers.
The concern with children is the same as with adults: petechiae combined with fever, lethargy, or a rapidly spreading rash needs prompt evaluation. Children are particularly vulnerable to meningococcal infections, and a non-blanching rash in a sick child is one of the classic warning signs that pediatricians are trained to take seriously. Isolated petechiae in an otherwise healthy, playful child after a coughing spell are a very different picture from widespread spots in a child who seems unwell.
Do Petechiae Go Away on Their Own?
Petechiae caused by straining or minor trauma typically fade within two to three days as your body reabsorbs the leaked blood. They may shift slightly in color as they heal, similar to how a bruise changes from red to brownish before disappearing. No treatment is needed for these cases.
When petechiae are caused by an underlying condition, the spots won’t fully resolve until the root cause is addressed. If low platelets are the issue, treating whatever is suppressing or destroying them allows the count to recover and the petechiae to clear. If an infection is responsible, treating the infection stops new spots from forming while existing ones gradually fade. New petechiae continuing to appear over days or weeks, or spots that keep getting larger, suggest the underlying cause is still active.