Haven't we all had some kind of allergies at different times?
My first experience was when I was about 22 years old, single, living alone, working an evening shift in the Dallas Post Office. I got off work, and got home about midnight, and got in the habit of fixing myself some bacon and eggs before getting a shower and going to bed. And about an hour or less after going to bed, I would break out with great big welts all over my body; looked like I'd been beaten with a belt, and itch terribly. It was an every night situation. So I saw a doctor who told me it was obviously an allergy and that he could run a lot of expensive tests OR I could experiment myself. So the first thing I did was quit eating at night when I got home; no more problem. Then one night when I got home I ate 2 boiled eggs and really suffered. Now I'd eaten eggs all my life so I have no idea how I became allergic to them. But I avoided them like the plague for more than a year, then eventually went back to eating them with no ill effects.
On one trip to Alaska in our fifth-wheel about 1991-92, I awoke one night in the middle of the night, itching all over intolerably. First I got in a tub of hot water that didn't help at all. And finally I called the Anchorage police department and asked directions to the nearest hospital. They offered to send me an ambulance, but I told them I thought I could drive myself, and did. At the hospital, they promptly gave me an injection that pretty quickly relieved the problem. I still have no idea what caused it. We had just been visiting my brothers there in town in Anchorage.
Then in the late ninety's I was mowing with a small bush hog and my little Kubota across the road from our house in Navarro County. It was brush and weeds higher than the hood on the little tractor and I began to feel like my face was swelling, so I put the tractor in the shop and went in the house to look in a mirror and my face was swollen and appeared to have some yellow liquid oozing out. I went to the emergency room and another injection that fixed the problem fairly quickly. Now I just had to go back a few days later and try mowing over there again to see if the problem would recur, but it did not.
Sometimes it just seems that there is no explanation.