many different reasons for such blotches.
it could be bug bites.
it could be poison ivy.
it can be chemical burns from being splashed.
chicken pox, or other viruses.
it happens. you have bumps.
you don't scracth them if they itch.
use baby diaper cream to cover them and they will clear up.
the key is to NOT SCRATCH or pick at them.
of, and if you see someone who has that, don't 'monkey around' with them.