Allergy?

Does this rash look like a possible allergic reaction? he tried salmon for the first time but two tiny bites, and almost 2 hours later this showed up. it’s not lumpy or anything and he did just have a bath and fell asleep in the car on the way home from grandmas so i don’t know if his face was rubbing against the head rest of his carseat. It’s only on one side of the face and no where else and acting completely normal otherwise