T.M.
The same thing happened to my son last year. Once he was on allergy meds (I tried Target brand of Claritin for kids), the problem went away.I know so many people who develop allergies in Dallas, and babies seem to be born with it.
The problem is your son might be too young for meds. Try to lift the head of his crib to make breathing easier during the night. Also, there might be something at his daycare or at home that triggers the allergies: certain cleaning liquids for example.
I hope your boy feels better soon, J J!