My son has red clusters of a rash popping up first his shoulder now face and legs. What could this be?

Hard to say? . How old is your son? What exposures to illness has he had this week? Any medicines that he takes? Any fever? Sore throat? Is the rash raised or flat? Any new detergents or soaps in his regimen? History of allergies or asthma? The answers to These answers to these questions will help us pinpoint a diagnosis. We may be able to help in a Prime visit. Best of luck! .
Hard to say. Can't te;; by just that info, need a visual and more details about other symptoms, etc.