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.
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.
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.
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.
The next rash is slightly more obvious.
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.
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.
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:
Other causes of a petechial or purpuric rash include:
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.
Last reviewed on 30 August 2011
|We comply with the HONcode standard for trustworthy health