My accidental cure for my Type IV food sensitivity was some curry I made with canned coconut milk that turned out to be "a bit off". That food poisoning gave my guts a good flushing out, and the next morning my food sensitivity was gone, after 2.5 years. My guess is that I had some microbe in my gut microbiome that was activating my immune system, and the flushing out gave my microbiome the opportunity to eliminate it completely. Antibiotics alone hadn't done the trick, because they may have reduced the beneficial microbes even more.
The other accidental cure was cumin (cuminum cyminum). I first noticed that something had blocked my expected morning increase in symptoms, after curry the previous night. Further experimenting identified cumin as being responsible. Taking a full teaspoon worth gave me temporary remission. After a couple of weeks of daily cumin, it stopped working. Years later I discovered that cumin could block my physically-induced PEM. After taking cumin every three days for a year or two, I found that I no longer got physically-induced PEM (can still get cerebrally-induced PEM). I had also been taking T2 or iodine every 21 days, to block otherwise worsening of my symptoms. That problem went away at, as far as I can tell, the same time as the PEM stopped, so I assume the cumin cured both problems.
Another accidental discovery was that my worsening of symptoms from eating meat could be blocked by taking carnitine. I had noticed that I had different sensitivities to different meats: I could tolerate up to 200 gms of beef, less than 30 gms of pork, and almost no chicken. Then I came across a list of foods containing carnitine, and I noticed that beef had lots, pork had about 1/6th that amount, and chicken had almost none, which was a suspicious match for my sensitivity. I tried supplemental carnitine, and it allowed me to eat meats without problems. I'm fairly sure that it was the palmitic acid in the meats, and carnitine is critical for transporting fatty acids across the mitochondrial membrane. After taking carnitine for a year or two, I no longer had a problem with meats without it.
My ME started with what seemed to be a type IV reaction to oranges. I had gotten a tetanus booster some months before that, which may have been the trigger. I'm not sure whether the type IV sensitivity was a result of ME or the cause.