Sulfite sensitivity/allergy

Can I ask what peoples experiences have been of this?
Do you know what has caused it, and how does your body react?
And does it wax and wane with your flares?
I ask because I get slightly worse after certain squashes, and I've had bad reactions to dental anesthetic in the past, but it can be ok sometimes so I have no idea whether it's a sensitivity, or just bad timing!
As usual, all your comments are appreciated!