dyer sheet allergic reaction

So my boyfriend just woke up saying that the blankets I just washed had dryer sheets stuck to them and that the dryer sheets got on him while he was asleep and it made him have an allergic reaction. (He claims he has hives but I don't see any. I think his skin is just irritated) so I told him to take some Benadryl and he does and then he goes right back to his bed and tries to go to sleep (we sleep in different beds long story) now my question is could he be allergic to dryer sheets only if they have direct contect? Or could it be something else? I use the same dyer sheets and laundry soap everytime I wash our clothes or blankets, but we never have this problem.