Every year starting in Aug. my dog gets allergy to something in grass, lasts for 2 mos, then goes away. Trim the hair on the paws, and wash his feet after being outdoors, vacuum frequently, try booties when outside, or a pair of socks attached over the shoulder by a ribbon. Smear cortisone cream/ointment between toes.
Grain/corn free food definitely, raw is excellent, can be bought frozen. For anal gland issues try adding bran or pumpkin for additional fiber in food. Larger bowel movement can help keep glands expressed. Good luck!