Many rashes in children come from common viral illnesses, eczema, heat, or mild allergic reactions, and clear up on their own. However, one type needs immediate attention: small red or purple spots or bruise-like marks that do not fade when you press the side of a clear glass against them. Combined with fever, drowsiness, a stiff neck, or a very unwell child, this can signal meningitis or sepsis and is a medical emergency.
Call your emergency number or go to urgent care for a non-fading rash, a rapidly spreading rash, or any rash with swelling of the lips, tongue or face, difficulty breathing, or signs of a severe allergic reaction (anaphylaxis), which requires immediate treatment.
For itchy, mild, or slowly appearing rashes in an otherwise well child, it is reasonable to monitor and ask a pharmacist or doctor. Note any new foods, medicines, or contacts. If you are ever unsure whether a rash is serious, treat the glass test as a safety check and seek help if in doubt.