Y child broke out with rash on his face neck and back what could it be

Hello Anon

Thank you for writing.

This rash could be due to allergies - a reaction to food, an insect bite, clothing or the environment. It can sometimes be caused by stress.
Look into what he was doing/eating/drinking in the hours before the rash started. If the rash doesn't clear up within a couple of days, take him to his doctor.
Best,
Susan