Purpura and petechiae are spots of skin discoloration that occur when small blood vessels under the skin break and bleed. The main difference between the two is their appearance.

Purpura and petechiae can both appear in rash-like clusters. An unexplained rash may require treatment, and any child with an unexplained rash and a fever should receive urgent medical attention.

This article describes purpura and petechiae and their key differences. It also explores their causes, treatments, and when to contact a doctor.

A person rubbing cream onto their legShare on Pinterest
Elena Noviello/Getty Images

Purpura appears as red, pink, purple, or discolored patches just under the skin. They are larger than 2 millimeters (mm). They can also develop under the mucous membranes, such as those in the mouth or nose.

Purpura forms when tiny blood vessels called capillaries burst and leak, causing blood to pool beneath the skin. They are also known as blood spots or skin hemorrhages. Though they are usually flat, they can be slightly raised.

In most cases, purpura develops in rash-like clusters on a single area of skin, which may be large. Generally, the larger the affected area, the more severe the underlying bleeding.

A purpura cluster is not generally irritating or itchy. The spots are also non-blanching, meaning they do not fade or change color under pressure.

As purpura heals and the body breaks down and absorbs the pooled blood, the patches change color. These changes vary — a spot may turn reddish-purple to brown, orange, blue, or green.

Purpura does not represent a medical condition. They are a symptom.

Learn more about purpura.

Petechiae appears as red, pink, purple, or discolored patches under the skin. They are smaller than 2 mm and usually flat.

Generally, petechiae are smaller versions of purpura, and they, too, are sometimes called blood spots. They form when capillaries break and leak blood that pools beneath the skin.

Like purpura, petechiae change color as the body breaks down and absorbs the pooled blood. The color transitions from reddish-purplish to brown, orange, blue, or green, and these spots do not fade or change color under pressure.

Petechiae can develop in small clusters or patches, resembling a rash. It may spread over a larger area of skin or stay confined to a single area. Petechiae can occur around or among purpura.

Petechiae in children

Petechial rashes can develop in children. According to estimates, 2.5% of children taken to the emergency room experience them as a symptom.

Pediatric petechial rashes can be harmless and resolve on their own. However, a healthcare professional doctor may need to treat the underlying cause.

Like purpura, petechiae are symptoms of a health issue. If a child develops an unexplained rash, it is important to consult a healthcare professional.

Learn more about petechiae.

The most obvious difference involves size: petechiae are smaller than 2 mm, while purpura are larger. Purpura may be petechiae that have spread and joined together, forming larger areas of discoloration.

Both petechiae and purpura clusters tend to have rash-like appearances. Though the spots are usually flat, they can be slightly raised.

There are three types of purpura, with petechiae being one type of it:

  • Thrombocytopenic purpura: These occur due to conditions that cause the irregular destruction of blood platelets — cell fragments that help the blood clot. Autoimmune conditions or certain medications or infections can have this effect.
  • Non-thrombocytopenic purpura: These occur with damage or rupturing of the blood vessels or with the loss of the skin’s structural elements.
  • Purpura from other clotting disorders: These disorders may relate to medication use, such as warfarin-induced necrosis or heparin-induced thrombocytopenia.

A wide range of factors can cause purpura or petechiae to develop, such as:

  • straining while coughing, vomiting, lifting something heavy, exercising vigorously, or using the bathroom
  • damage from UV light
  • skin aging, leading to a loss of collagen
  • laser treatments
  • vitamin K deficiency
  • vitamin C deficiency, known as scurvy
  • allergic reactions, such as those caused by insect bites
  • medical procedures and surgeries
  • skin damage or trauma
  • blood vessel damage

Medications

Certain medications can cause purpura, including:

Other health conditions

Several autoimmune conditions or health issues that cause irregular bleeding or affect blood clotting can cause purpura. Among them are:

  • Sjogren’s syndrome
  • lupus
  • Schamberg’s disease, which causes blood vessels in the skin to leak
  • Finkelstein’s disease, which causes severe hemorrhaging and swelling
  • Wiskott-Aldrich syndrome, which impairs blood clotting
  • Bernard-Soulier syndrome, which also impairs clotting
  • Glanzmann thrombasthenia, a bleeding disorder
  • idiopathic thrombocytopenic purpura, a clotting disorder

Many other medical conditions that can cause blood vessels to burst or leak can also cause purpura and petechiae, including:

Infections can also cause blood vessel damage and lead to purpura and petechiae. Some of these infections and pathogens include:

The key to treating purpura and petechiae is to address the underlying cause. This treatment may involve:

Purpura or petechiae resulting from minor injury often do not require medical attention, as they usually heal independently. If there is pain or swelling, the following may help:

  • taking over-the-counter pain medication, such as acetaminophen (Tylenol)
  • applying an ice pack wrapped in cloth for 15–20 minutes at a time
  • avoiding activities that strain or put pressure on the affected area
  • staying hydrated and having a healthful, balanced diet
  • resting

Unexplained rashes of any kind require medical attention, especially in children. Seeking emergency care is crucial if a child has an unexplained rash and a fever.

People who develop purpura, petechiae, and additional symptoms should also contact a doctor.

Both types of discoloration have associations with underlying health conditions, many of which require medical treatment. Receiving a prompt diagnosis and treatment reduces the risk of serious complications.

What is the difference between petechiae and purpura?

Petechiae is essentially a type of purpura, just with a smaller diameter.

What is the leading cause of purpura?

The leading causes of purpura and petechiae include damage to the skin or minor injuries, aging, certain medications, infections, and overall damage to the blood vessels.

What deficiency causes petechiae and purpura?

Deficiences in vitamin K and vitamin C can cause petechiae and purpura.

Purpura and petechiae appear as discolored spots on the skin that appear in rash-like clusters. Both result from blood vessels breaking and leaking. Purpura are larger than petechiae. Purpura may develop when numerous petechiae join together.

There are many possible causes of purpura and petechiae, from a minor injury or medication to an infection or genetic condition. Overall, it is important to contact a doctor about any unexplained rash.