It is common for individuals to be more sensitive to allergenics as they age the top allergenic foods are:
Wheat (gluten)
Dairy
Peanuts
Fish (Bass, Cod, Flounder)
Shellfish (crab, lobster, shrimp)
Soy
Tree Nuts (Almonds, Cashews, Walnuts)
Citrus Fruits
knowing this it would behove one to cut out all the above from thier diet for 2 weeks and one by one add the above and take note of your reaction...often the reaction will be intensified as the 2 week period has allowed the mucus and inflammation to leave your digestive tract and the symptoms will be enhaced.
It is best NOT to eat these foods if you are allergic to them or even sensitive as they limit the bodies ability to absorb proper macro and micro nutrients...
When I cut out the obove I was noticeable leaner without changing my cals and I recover better from training...also muscle gain increased as well (not super dramatic, but I decreased BF by 5% and only lost 5 lbs)