Can severe seasonal allergies cause an enlarged thyroid, or can a malfunctioning thyroid in a type 1 diabetic cause severe seasonal allergies?

Allergies and thyroi: Generally not but they can cause lymph swelling that may feel like enlarged thyroid. As well. A malfunctioning thyroid may cause a variety of symptoms ( depending if over or under active) that may feel like allergic symptoms. I would suggest a trial of OTC antihistamines and also an evaluation of the thyroid (blood test) as a start. Good luck

No: Seasonal allergies to trees, grasses and pollen should have no direct relationship with the thyroid gland or thyroid function.