Grid pattern rash on back

[Kelta]

We are currently on holiday and i have noticed a grid pattern rash on DS2s back. I initially thought it was an imprint from a sunbed or even an area that has tanned more somehow from a chair or sunlounger but it isn’t because we’ve checked everything.

any thoughts on what a grid like rash could be? The area is about ten cm x eight cm

Yes I’ve seen all the alien abduction suggestions. Apparently if they are accompanied by a vivid dream that proves it’s an alien abduction.

So update it is most definitely a rash. It’s a slightly larger area today

Have you looked at the bed sheets? An under layer?

Is it from not moving on the sunbed (albeit in the shade) and wearing synthetic fibres? Looks like he’s aggravated follicles and it’s raised.