Help! My son woke up like this..

Heather

What could this be? Haven't changed anything such as soap, laundry detergent, food..

UPDATE:: thank you everyone that responded! I swear being a first time mom I worry about EVERYTHING!!! Anyways, I called his pedi and she did not seem concerned since he had no fever and was eating/drinking normally. The rash was completely gone the next day.🤷🏽‍♀️ I still have no idea what it could of been from..,🤔