@GreyOwl and
@Wishful How would this (type IV hypersensitivity) compare to an IgE allergic response or to a mast cell response? What symptoms do you get when you eat an orange
@Wishful and are they immediate or delayed?
There's really not much in common between the two types, aside from both being a reaction to a chemical trigger. Type IV takes 48-72 hrs for symptoms to show up, whereas type I allergies are fairly immediate. One alternative medicine allergist wanted to do scratch tests for my type IV reaction. I asked how that would work when it took 48 hrs to do anything, and it didn't cause histamine bumps. He couldn't answer that, but insisted it would work. I didn't bother booking a test.
The first few times I had a severe reaction, it seemed exactly like a regular flu, which shares some symptoms with CFS. The severity gradually declined from full flu-like, but still seemed the same. I spent years describing it to doctors as 'flu-like symptoms'. I assumed it was some kind of chronic t-cell-mediated inflammation. In retrospect, I realized that I had had very slight but consistent reactions to oranges since at least early 20's. It was just a few sneezes and a slight feeling of a cold coming on, lasting only a day or so, so I just wrote it off as regular colds and a very good immune system.
I no longer have reactions to oranges...I think. The type IV sensitivity vanished after a typical bout of food poisoning (spoiled coconut milk in curry). I'm just avoiding citrus, cherries, and other similar fruit just in case the sensitivity might possibly reoccur.
If you were wondering if you were having symptoms of type IV sensitivity, for me they were identical to having a flu, and they started with a precise and consistent 48 hr delay (+/- a few minutes). I think it's hard to mistake for anything else. The delay did change abruptly twice (to 17.5 and then 23.6 hours), after unusual circumstances, but stayed +/- a few minutes. None of the papers on type IV sensitivity mentioned delay changes, but there's not much research in that area, so it's still mysterious.