It could be food intolerance but I have also suffered die-off from eating lots of onions. They are antifungal same as garlic (although not as strong).

I was going to say the same thing Steh- onions are part of the Sulfur foods group.
Could be other foods in the same group that cause sensitivities/reactions too.
Sulfite foods can be a problem too.
I didn't know until I had the food sensitivity test done, that corn syrup/high fructose corn syrup was high on my list--and the way it is processed, it becomes a sulfite.

Quoting Andrew Cutler- again, he has good information:

>>>If something is giving you trouble, you need to figure out what it is and limit or exclude the relevant foods. You can be allergic to more or less anything. If you have trouble with foods in the following classes, it is not an allergy problem- it is because your liver is not metabolizing one of the basic components in the food.

Sulphur Foods:
---eggs
---dairy products
---bakery products containing whey
---cysteine
---beans
---peas
---legumes
---peanuts
---cabbage
---bok choy
---cauliflower
---broccoli
---broccoflower
---brussels sprouts
---kale
---turnips
---rutabagas
---asparagus
---onions
---shallots
---leeks
---garlic
---chocolate
---coffee