Take him off wheat and all cereal grains for 3 months. AlLso no dairy- obviously. It will be tough but you need to try to feed him as much raw fruit and vegetables as you can get down him.
Basically you need to let his immune system rest. There are many supplements out there in liquid or sublingual form. Basics would be Vitamin C, cod liver oil, B complex... If my kids start to get a sore throat I make them go out side and open their mouths. Good 'ol UV kills all kinds of bacteria especially in warm dark places.
Allergies are usually in response to foreign proteins so consider all animal products to be suspect. It would even be helpful to use a digestive enzyme with his meals so that the molecules are broken down into their smallest components. Beano is liquid bit I think only works on carbohydrates. Look for a liquid that works on all three- fats, proteins and carbohydrates.
Anyway, you can probably fix this yourself with some work. Just think in terms of cleaning up his diet, his air and his environment. No chemicals, use only pure soaps and as little as possible. You may need a chlorine filter for the bath water...anything that stresses his system- remove. You can use 20 Mule Team Borax for laundry and soap.
Good luck,
M