A child's skin is a constant theatre: heat, viruses, allergies, nappies… The reassuring rule: a rash with a mild bug in an active, playing child is usually innocent. The key is learning the glass test and knowing the "bad companions" that turn a rash into an alarm.
In short — what to do
- Take a clear glass and press its side firmly against the rash.
- Rash disappears or fades under pressure? Usually a superficial, innocent one.
- Still visible unchanged under the glass? That's a non-blanching haemorrhagic rash — ER immediately, especially with fever: it can be meningococcal disease.
- Also check: tiny red/purple pinpoint spots (petechiae) that don't fade = the same alarm.
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The full details
The glass test
- Take a clear glass and press its side firmly against the rash.
- Rash disappears or fades under pressure? Usually a superficial, innocent one.
- Still visible unchanged under the glass? That's a non-blanching haemorrhagic rash — ER immediately, especially with fever: it can be meningococcal disease.
- Also check: tiny red/purple pinpoint spots (petechiae) that don't fade = the same alarm.
When does a rash need a doctor soon (not the ER)?
- Rash with fever beyond 5 days (to exclude Kawasaki).
- A very painful or ulcerating rash, or around the eye with swelling.
- Rapid spread within hours, or a child more tired than expected.
ER immediately (998) if the rash comes with
- A non-blanching rash + fever — don't wait to re-test.
- Lip or face swelling or breathing difficulty — severe allergy (see the allergy guide).
- Stiff neck, marked drowsiness, repeated vomiting, or light discomfort.
- A child who looks "very ill": pale, cold limbs, not interacting.
One moment
A clear glass in every home is the world's cheapest medical alarm — teach everyone who cares for your child this test, because the rash that doesn't blanch waits for no one.
This content is for general health education only and is not medical advice. Always seek guidance from a qualified healthcare professional. In an emergency, call 998.