When I stopped eating vegetables, my allergies went away. It was pretty crazy. I did carnivore for a few months in a desperate attempt to heal some autoimmune issues & one of the biggest surprises to me was how clear my nose became. I didn’t know my nostrils could be so clear that breathing in just air could feel like water up the nose. I’ve since added carbs - but for the most part no allergies except for when I’ve added in leafy green veggies. Everyone’s chemical make up is different & another person could be total opposite - but what I have taken from the experience is that if there are severe food sensitivities that we continue consume then the gut is weak & triggered which then makes us susceptible to being triggered by our environment. Maybe there’s a food allergy in there that if he stopped eating it & his gut were healed, then his environmental allergies might also dissipate.