There are 3 of us in my sibling group (me and two others) our parents have absolutely no allergies of any kind, not medicine, food or even hay fever. All 3 of us have severe and life threatening allergies to foods and medicine. All the allergies are different mangos, gluten, strawberries, peaches, seafood, citrus (and olestra a fat substitute not sure if that should be in the food catagory) are the combined food allergies we have. In addition to the serious ones some of us are also allergic to some different soaps and get body hives from them.
We were not raised in an overly clean environment (sometimes our environment was down right filthy by anyone's standards) we didn't have the luxury of being picky eaters, it was eat what was provided or not at all situation, we were not kept indoors, most of our youth was spent outside. I do not know for a fact but am pretty sure we were formula raised children. Nearly all our allergic reactions happened as adults or late adolescence.
The only allergy I can directly attribute to genetics would be mine to penicillin, even though my mother didn't have that allergy her mother did.