Question: If my child is allergic to a food, does he/she need to avoid the oil for that food (e.g., peanut, soy, tree nut oils)?
Answer: Well, this is an area of great confusion and one that can, in some instances, make a family's life very difficult, if they're avoiding foods they really don't need to. And in other instances may cause risk of an allergic reaction.
So, if we broke down those examples you gave, children who are allergic to things like soy and corn and safflower, which are the most common forms of vegetable oil in the market, are almost never allergic to those oils. And the reason that can happen is that what you're allergic to in the food is the protein, and if an oil has been highly purified, the protein has been removed so that only the fat component is remaining. And in that case, even someone with a severe soy or corn allergy would be okay with those oils.
Peanut oil is different in that some peanut oil on the market is not highly processed and is a great danger of children with peanut allergy. So whereas most peanut oil is okay, we recommend that all children with peanut allergy avoid all peanut oils because of that true risk with some of the oils.
Tree nut oils are all unprocessed oils. The processing removes a lot of flavor. The nut oils are meant to keep their flavor so all tree nut oils, things like walnut oil, would be a risk. And the same would be true for sesame oil for patients with sesame allergy.