Can anyone identify this rash on DS (10)

[bakingbee]

I'm drawing on the collective wisdom of MN's
DS has a strange patch of rash on his back. Any suggestions?

Could it be a bruise or a friction rub? Looks quite like what I've seen on my DC's backs after they've gone down a squeaky slide or something...

It wouldn't worry me (and I would think injury not rash) unless it spreads or appears in other places too.

I agree with @BlackInk this looks more like an injury than a rash

From a squeaky slide or those itchy school/nursery carpets

Hope he is okay, is he old enough to ask what happened?

He wasn't aware of it at all so no pain or itchiness. It's under the skin as opposed to on the surface iyswim. He's totally fine in himself - few similar red dots the other side of his back this morning (not clustered like this one) but hasn't spread ...

Funnily enough my 9 year old DS appeared with a rash very similar to this! Very itchy and took a couple of days to disappear

Oh that is similar apart from the itchiness. I guess I'll just wait for it to disappear as quickly as it came!
Thanks all