just wanted to point out that, while you cannot give your DC an allergy you most certainly CAN give them an intolerance by not exposing them to certain foods.
ie, if you are vegetarian and DC eats veg and suddenly eats a burger they will be sick, not because of allergy/intolerance but because they are not used to meat and their gut will not have be able to cope with it.
Your gut adapts and makes physiological changes to the bacterial community based on what you put in it. I have lived in London three years and to this day cannot eat a ready meal, not even a fancy one, without getting ill... not adapted to something in them I suppose.
I do worry about this with DD as DH and I both hatehatehate fish so she gets none at home. Trying to figure out ways to incorporate it or somehow branch out because I don't want to limit her food choices because of my tastes.
Obviously this wouldn't apply to non-food allergens and if someone is already at a high immuno response trying to reduce the other strains on their systems (such as foods they are sensitive to) often gives them the boost they need to deal with the more important stuff, so I would never tell someone to NOT try a limited diet if they are dealing with an allergy problem.
just throwing that out there.