Any ideas what this might be

[redpurple]

Obviously will seek medical advice if I feel necessary, but I've just noticed this on my child behind their ear.

Already had chicken pox, though I know it isn't impossible to get it again.

Nothing anywhere else on the body.

Any ideas what it is?

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Looks like some kind of allergy or bites. If it’s itchy I’d topical antihistamines

Agree - looks like a bite or hives.