I would start with the elimination diet as well as going to free and clear detergents and gentle, natural soap and shampoo.
Also try to allergy proof the bedroom where he sleeps. Cover it with an allergen-proof matress cover. If you can't afford that, get a cheap vinyl mattress cover that goes all the way around the mattress and zips. You can get them for around $15 at Target. Do the same with pillows. Wash *all* bedding at least once a week, hot wash, hot dry, and don't forget stuffed animals that are in the bed. Have him take a bath before bed every night and put on clean PJs. Vaccum and dust regularly and make sure the bed is away any air vents and windows.
Ear infections have many causes but some of the leading causes include allergies and reflux. First, it causes the mucous to build up in the body including the sinuses and the ears cannot drain and get infected. Secondly allergies to foods can cause digestive problems, which in turn may cause him to reflux up into his throat and beyond. My dd has severe reflux, environmental allergies, and recurrent ear infections. She now has ear tubes and they are helping a lot. There is a strong connection between allergies (asthma/eczema), ear infections, and reflux.
7yo: "Mom,I know which man is on a quarter and which on is on a nickel. They both have ponytails, but one man has a collar and the other man is naked. The naked man was our first president."