Snuffles isn't really the name for the disease. It's an upper respiratory infection usually caused by the bacteria pasturella. Pasturella is always present in a rabbit's system, but the immune system keeps it in check so that there isn't an active infection. If he has been stressed out lately, it could have become an active infection.
The best way to treat it is to have a vet swab the mucus and grow the bacteria on a plate. They then try to kill it on the plate by adding different kinds of antibiotics. This is called a culture and sensitivity test. The antibiotic that succeeds at killing the bacteria on the plate will be prescribed to your bunny. It's really hard to treat this any other way, as many strains of pasturella are resistant to many common antibiotics, and the sensitive GI tract of a rabbit can have real problems with some antibiotics.
It may just be allergies, but that is usually a clear mucus discharge, not one that is whitish. If it sticks around for a few days, I'd take him in to a rabbit vet. It's really the best and only thing you can do.