Antibiotics are terrible for you. If you can treat it with something else, then you should. Antibiotics should be a last resort and even then taken with I forget which supplement to couteract the bad stuff it does to you.
He has an infection not allergies. That's why he should go to an ENT to make sure it is an infection not a cold or the flu, if so the proper course is antibiotics.
If he gets 4 or 5 infections a year he should consider sinus surgery. I had it 2 years ago, while it didn't fix my allergies and I still live on sinus medication, I haven't had a sinus infection since the surgery.
With that said, it is not a pleasant surgery. Try pinching your nose and breathing through your mouth for 1 hour much less 3 days.