Petechiae are tiny, flat red or purple spots that appear when small blood vessels under the skin break and leak blood into surrounding tissue. They measure less than 4 millimeters in diameter, roughly the size of a pinpoint, and they don’t fade when you press on them. The causes range from completely harmless straining to serious blood disorders and infections, so understanding the context around them matters more than the spots themselves.
How Petechiae Differ From Other Spots
The key feature of petechiae is that they don’t blanch. If you press a glass against the spot and it stays visible, that’s a non-blanching lesion. Regular rashes caused by dilated blood vessels will temporarily disappear under pressure. Petechiae won’t, because the blood has already escaped from the vessel and is sitting in the tissue.
Size also matters for classification. Spots under 4 mm are petechiae. Spots between 4 and 10 mm are called purpura. Anything larger than 1 centimeter is an ecchymosis, which is essentially a bruise. All three involve the same basic process of blood leaking from vessels, but the size and pattern help narrow down the cause.
Straining and Physical Pressure
The most common and least worrisome cause of petechiae is simple physical strain. Forceful vomiting, intense coughing fits, heavy crying, or bearing down during childbirth can spike pressure inside the tiny blood vessels of the face and neck. This is sometimes called the “mask phenomenon” because the spots appear in the loose skin of the face and around the eyes, almost like a mask pattern. The same thing can happen during strenuous weightlifting or even prolonged straining on the toilet.
These strain-related petechiae are localized, meaning they only show up in the area where pressure built up. They typically resolve on their own within a few days and don’t signal an underlying problem. If you see petechiae only on your face or upper chest after a bout of vomiting or coughing, that’s the most likely explanation.
Low Platelet Count
Platelets are the blood cells responsible for clotting. When your platelet count drops low enough, small vessels can leak without any obvious trigger. Spontaneous petechiae, easy bruising, and prolonged bleeding from minor cuts typically begin when platelet counts fall between 20,000 and 50,000 per microliter (normal is 150,000 to 400,000).
A low platelet count, called thrombocytopenia, has many possible causes on its own. Your body might not be making enough platelets due to bone marrow problems, or it might be destroying them faster than normal. Immune thrombocytopenia (ITP) is one well-known example where the immune system mistakenly targets platelets for destruction. Leukemia and other cancers that crowd out the bone marrow can also suppress platelet production. Liver disease and heavy alcohol use are additional contributors, since the liver plays a role in platelet regulation.
Medications That Trigger Petechiae
Several common medications can lower your platelet count enough to cause petechiae. Heparin, a widely used blood thinner, is the most frequent culprit for drug-induced platelet drops. Chemotherapy drugs and the seizure medication valproic acid also carry this risk.
Beyond those, a surprisingly broad list of drugs can trigger the same problem:
- NSAIDs like ibuprofen and naproxen
- Certain antibiotics including penicillin and sulfonamides
- Quinine, found in tonic water and some malaria medications
- Statins used for cholesterol management
- Furosemide, a diuretic
If petechiae appear shortly after starting a new medication, that timing is worth noting. The spots typically resolve once the medication is stopped, though your doctor needs to be the one making that call.
Infections
A number of viral and bacterial infections can cause petechiae, either by directly damaging blood vessels or by disrupting platelet production.
Viral infections are a frequent cause, particularly in children. Common culprits include Epstein-Barr virus (the cause of mono), cytomegalovirus, and some strains of influenza. These infections can temporarily suppress platelet counts or inflame blood vessel walls, both of which allow blood to seep through.
Bacterial infections are the more dangerous category. Meningococcal disease is the most urgent example. In meningococcemia, bacteria flood the bloodstream and damage vessel walls rapidly. Fever and a spreading petechial rash appear early, and the condition can progress to widespread purpura and circulatory collapse within hours. Roughly 50% to 60% of patients with meningococcemia develop petechiae or purpura. A petechial rash combined with high fever and neck stiffness is treated as a medical emergency because meningococcal infection can become fatal very quickly.
Endocarditis, an infection of the heart valves, and Rocky Mountain spotted fever are other bacterial infections associated with petechiae.
Vasculitis and Autoimmune Conditions
When the immune system attacks the walls of small blood vessels, the resulting inflammation causes them to leak. This is vasculitis, and the hallmark skin finding is “palpable purpura,” spots that you can actually feel as slightly raised bumps rather than flat pinpoints. These tend to appear symmetrically on the lower legs.
IgA vasculitis (formerly called Henoch-Schönlein purpura) is the most common form in children. It produces raised, round spots on the legs and buttocks, sometimes with blistering. In adults, similar patterns can appear with other forms of vasculitis including cryoglobulinemic vasculitis, which also causes cold sensitivity in the fingers and toes.
Lupus is another autoimmune condition that can produce petechiae through multiple pathways. It may lower platelet counts directly, trigger vasculitis, or cause kidney involvement that disrupts clotting. If petechiae on the legs are accompanied by joint pain, fatigue, or dark or foamy urine, an autoimmune process becomes more likely.
Vitamin C Deficiency
Vitamin C is essential for building collagen, the protein that gives blood vessel walls their structure and strength. Specifically, vitamin C enables individual collagen strands to twist together into the rigid triple-helix shape that makes the protein functional. Without enough vitamin C, collagen remains unstable, blood vessels become fragile, and blood leaks into the surrounding tissue.
This is the mechanism behind scurvy, which produces petechiae alongside bleeding gums, poor wound healing, and joint pain. While scurvy is rare in developed countries, it still appears in people with very restricted diets, chronic alcoholism, or conditions that impair nutrient absorption. The petechiae of scurvy often cluster around hair follicles on the legs.
How the Cause Gets Identified
The pattern and distribution of petechiae give important clues before any lab work happens. Spots limited to the face and upper chest after straining point to a mechanical cause. Widespread petechiae across the trunk and limbs, especially with bruising, suggest a platelet problem. Raised spots concentrated on the lower legs point toward vasculitis.
The standard starting test is a complete blood count (CBC), which reveals the platelet number, white blood cell count, and hemoglobin level. If a clotting disorder is suspected, tests measuring how long blood takes to clot can identify factor deficiencies, vitamin K deficiency, or liver disease. When infection is a concern, blood cultures, inflammatory markers, and sometimes kidney and liver function panels get added. A urine test checking for protein can help identify kidney involvement from conditions like lupus or IgA vasculitis.
The combination of where the petechiae are, how quickly they appeared, what other symptoms are present, and what the bloodwork shows is usually enough to point toward a cause. Isolated petechiae on the face after vomiting need no workup at all. Unexplained, widespread petechiae with fever, fatigue, or abnormal bleeding warrant prompt evaluation.