I was talking to a friend the other day about food allergies, and she insisted that her boyfriend “made himself” allergic to apples by eating lots of them as a child. I told her I didn’t think it worked that way, because if it did, I’d be allergic to loads of different things. She responded by citing tons of different people she’s known who have made themselves allergic to various things by eating them to excess.
Can you help me out here? I told her I’d ask on the SDMB and let her know my findings.
If anything it would be the other way around. Kids who grow up in cities, not exposed to animals and plants and germs are much more prone to developing allergies than kids raised in the country exposed to all those things. I have never heard of anyone developing an allergy just by being exposed to something too much. Never. On the contrary, the body tends to develop tolerance for drugs and other poisons, not allergies.
It is a common recommendation that very small children not eat certain foods until their immune system matures a bit. So eating some/ a lot of an allergy-prone food at a very young age is thought by some to contribute to an allergy. In your friend’s case, this theory would be that if he’d waited longer to eat apples, his immune system could have handled them and he wouldn’t be allergic today. That doesn’t seem to be exactly what your friend is describing, though.
Some food allergies, such as gluten (wheat) intolerance, can be influenced by how much of a particular food you eat. Someone who is genetically predisposed to be gluten intolerant may “trigger” the problem by increasing the amount of gluten they eat.
So your friend isn’t completely off track. But as far as I know, most food allergies don’t work this way.