Any idea what this could be on my DS’s back

[Eminybob]

He says it doesn’t itch, it doesn’t hurt, it just feels a bit weird.

It’s nowhere else, just this line of raised spots, a couple of inches long right in the middle of his back.

I’m not saying she’s wrong but my son’s was a patch slap bang in the centre of his back, that the pharmacist thought were probably infected bites.