R.D.
I would contact the director of the school and list these things as SEVERE ALLERGIES. People don't play around with allergies anymore. In my kids old preK, they would make any child with an allergy wear a bright yellow wrist band with a list of their allergies.
Chances are, your son's school is used to FOOD allergies, not contact allergies, and they're adjusting to this new thing as well. Not saying they're taking it lightly, but they're learning, you know? So contact the director AND the teachers, and make sure they list these things as severe allergies.