This looks like roseacea I'm not sure if I spelled it right it happens when they are getting over a fever or cold sometimes but take him to the doctor to confirm

@anmlopez, no his last shots where on the 10th this month, @rhealize, thank you I'll keep a eye on it

Dramatic change in weather does that to my kids. Detergent is likely if you're using a new kind. Or if you're using too much in a load. Put some lotion and/or benedryl cream on it for now and if it gets worse you can call his doctor about it. It looks like a mild case of hives though.

Any vaccines recently? That's what happened to my baby after vaccines

@dreamie702, that could be it I didn't change detergent and washed clothes yesterday and it just appeared today