What Causes a Petechial Rash in a Child?

A petechial rash (or purpuric rash) has some characteristic features, namely that the rash doesn't blanch (go white) when pressure is applied, eg, by the glass test.

This page has information on petechial and purpuric rashes as well as photos showing you what they look like.

Petechiae and purpura which cause petechial and purpuric rashes are caused by bleeding into the skin layers. Petechiae are small (usually less than 3 mm in diameter) and purpura are larger (usually 3 - 10 mm in diameter). Similar rashes that are larger still, so more than 10 mm in diameter, are called ecchymoses (but I'll keep it simple by just referring to petechiae and purpura on this page).

Sometimes a rash that is petechial initially becomes purpuric as it advances so both rashes can be seen in the same patient, or either one of them may be seen alone in other patients.

What is a petechial rash?

It is a rash with petechiae, which are red/purple spots that don't blanch on pressure - so when you push on them, you still see them.

The glass test is best for showing this - you press on the rash with a glass and you still see the rash through the glass even with pressure.

This can be a very serious rash, so please read this page carefully if your child has a red or purple rash that doesn't disappear when you press on it, and then act immediately.

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What do petechiae look like?

Petechiae are small red/purple spots that appear on the skin and don't disappear when pressure is applied. They are less than 3 mm in diameter, so can be quite subtle.

There are several photos on this page to illustrate petechiae and the glass test. Some of the rashes are obvious and some are subtle and are just like tiny pin pricks - the one thing they have in common is that they still appear under the glass even with pressure - so they do not blanch with pressure.

When the petechiae are larger (so more than 3 mm in diameter), they are referred to as purpura, so the rash is called purpuric rather than petechial.

The petechiae and the purpura are caused by bleeding into layers of the skin.

petechiae1APetechiae
petechiae1AaGlass Test

As you see in these photos, this rash is very subtle and just like a pin prick but it remains when pressure is applied. See below - it's the same rash but I've identified the petechiae.

Petechiae1BPetechiae
Petechiae1CGlass test

The next rash is slightly more obvious.

PetechiaePetechial rash
PetechiaeGlassTestGlass test

The photo at the bottom of the page shows a more extensive rash that are unlikely to be missed - an extensive purpuric rash (with some ecchymoses). The rash is a case advanced meningococcal sepsis, which is a very serious disease because it progresses very rapidly and can cause death if not treated in time.

Those rashes are quite obvious. However, that is not always the case as you see in the first photos. Sometimes, there are just tiny pinprick red dots - the key to it being a petechial rash is that when you push on the spots/dots, they don't blanch (go white) - so you still see them when the glass is pressed on. You need to be vigilant and if in doubt about a red/purple rash, apply the glass test and get urgent medical attention for rashes that don't blanch.

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What is purpura?

Purpura (or a purpuric rash) refers to the same sort of rash as a petechial rash but the spots are larger (more than 3 mm in diameter) and it is often more purple than red. So a child may have some small petechial spots and some larger areas of purpura.

Petechiae2APurpura
Petechiae2AaGlass test

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What causes a purpuric or petechial rash in a child?

There are many causes but some are serious and so if your child has a rash with petechiae or purpura, you need to seek urgent medical attention in case it is caused by a serious condition.

Serious causes of a petechial or purpuric rash include:

Thrombocytopenia purpuraIdiopathic thrombocytopenia purpura
  • meningococcal infection - the rash may start off as a blanching rash and your child may have fever. The rash can appear before your eyes. This is a very serious condition and can cause shock and death. Seek urgent medical attention
  • idiopathic thrombocytopenia purpura - the rash is often more purpuric than petechial usually. Your child may just start off with large bruises that occur easily. The condition is caused by low platelets, which are the clotting cells in the blood. It usually resolves by itself over time, but sometimes treatment is required. See your doctor to confirm that this is the condition
  • leukemia - this is a cancer of the bone marrow and causes low blood cells, including the clotting cells. Children may also be pale and prone to infection. Treatment is successful so see your doctor early
  • severe infection - any infection if severe enough may interfere with the normal body clotting system and if your child is sick and has a petechial or purpuric rash, you need to seek urgent medical attention


Other causes of a petechial or purpuric rash include:

  • viruses - particularly enterovirus infection
HSP-rashPurpura of HSP
  • Henoch-Schonlein Purpura (HSP) - a condition that involves the skin, joints, gut and kidneys. It usually resolves by itself and no treatment is required but it is helpful to see a doctor to confirm the diagnosis and check if the kidneys are involved
  • pressure - such as tight clothing
  • forceful vomiting or coughing - if this is the cause the rash is on the upper chest or face only

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Can my child get meningococcal infection if she has been immunized?

meningococcaemia3Meningococcal septicemia

There are several types of meningococcal infection and children are usually only immunized (vaccinated) against one type so it is possible for your child to get the infection if she is immunized.

Different countries immunize against different type of meningococcus depending on what one is the worst health problem for them.

If your child develops a petechial rash, take it seriously and seek medical attention urgently. It is better to be safe.

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Last reviewed on 30 August 2011

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Dr Maud MD

Dr Maud MD (MBChB, FRACP, FRCPCH), a specialist pediatrician, provides health information and medical advice for parents of babies and toddlers. Read more about Dr Maud.



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