Unexplained rash - allergy test? (Pic)

[TennesseeTravis]

Shamelessly adding a picture to increase traffic.

10 year old child came out in rash after being in park earlier. Looked worse as this pic is after an antihistamine pill and lotion and was red, bumpy and itchy.

Thankfully it almost completely went after a few hours. Apart from being a bit scared DS was fine in himself; didn't feel poorly or have trouble breathing.

My concern is that this came completely out of nowhere! What could have caused it? Ivy?

He doesn't have any food allergies etc that we are aware of but given he is growing up and going away to scout camp and school residentials etc I wonder if I should get him allergy tested. Or maybe I just sent him off with piriton and lotion and hope for the best. Thoughts/ advice please!

We are in England despite username!

Looks like an allergy rash alright, maybe even a heat rash of sorts?

Have you recently changed anything he uses? Body wash, lotion, fabric softener, etc?

Thanks for replying. Must be something from the park - doubt it's heat rash, it wasn't from very hot! Anyone know if English ivy can cause this reaction?

My DS had a similar looking rash but was quite poorly with it. Turned out to be scalded skin syndrome - caused by a tiny bit of dirt / Earth going into a tiny cut he had on his hand. He was tiny though at the time so probably took it worse.

You can only really do allergy tests if you have a reasonable idea of what they may have had an allergy to. It's not feasible to "test to everything".