I suspect chronic allergy problems can be caused by parathyroid dysfunction and / or low cortisol. When I had allergy issues that just progressively got worse, I found through blood testing that I had sub-optimal Vitamin D levels. When I normalized my Vitamin D levels through supplementation, my allergy problems practically disappeared for years, only to finally resurface now the past couple of weeks.
My theory is that if Vitamin D is low, calcium absorption in the gut is poor, and parathyroid has to release hormone to stabilize blood calcium levels. I believe this hormone is linked to mast cell activation.
My other theory is that low cortisol can cause allergies to go berserk, but I don't have much evidence to go on for that other than feels.