What is this rash?

[Allisgood1]

Ds (7m) is covered in this rash head to toe. It looks different on his hands than his tummy (bumpier). Any ideas? No fever, but fussy. He isn't scratching at it.

My DD gets similar when I change my washing powder. Have you done that? Or has someone else washed his clothing? Maybe he's slept on something different?

Allergy?
Suncream?
Washing Powder?
Heat rash?