Blanching and Non-blanching rashes

Rashes can be divided into 'blanching' and 'non-blanching'. The group called 'blanching' disappears when you press it. The group called 'non-blanching' doesn't disappear when you press it. A 'petechial' rash is a non-blanching rash that is very small, like pin pricks. How do you tell the difference?

The glass test

The way to tell if a rash is blanching or non-blanching is to place a clear drinking glass over the rash and press down. If you can still see the rash through the glass, it hasn't disappeared and is, therefore, a non-blanching rash. If you can't see the rash anymore, it has disappeared and is therefore, a blanching rash.

For more information on the importance of non-blanching rashes, see 'Rashes' in the symptoms section.

a blanching rash A blanching rash

press a glass against a blanching rashPress a glass against a blanching rash and it disappears, you can no longer see it

a non-blanching rashA non-blanching rash

press a glass against a non-blanching rashPress a glass against a non-blanching rash and it doesn't disappear, you can still see it

Snotty Noses is written by Dr. Orlena Kerek, paediatrician and mother of four.

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