Many years ago, when my middle daughter was in 5th grade, she began to experience headaches that often affected her for hours or even days. A natural practitioner-friend suggested that we check to see if it was some kind of allergy and instructed us to keep her off of wheat, eggs, milk products, chocolate and one other item -- which I can't remember now -- which are known allergens.
The idea was to clean out her system and then reintroduce the products back into her diet, one by one.
I remember, at the time, thinking "if it has to be one of my kids, it's a good thing that it's this one, because she's the only one who would put up with this kind of limitation. In the end, the headaches disappeared and her diet returned to normal, but I think of that incident often because she is still the most disciplined one of my kids when it comes to food.
Yochi is now at university and has become a vegan. She was a vegetarian for many years but starting several months ago, decided that veganism made more sense, so she's cut all eggs and milk products out of her diet.
Soy milk and tofu can substitute for a lot of the dairy, but how do you substitute for eggs? Yochi comes home every few weeks and, while she's pretty undemanding, we want to make sure that she has a nice time while she's home -- much of which revolves around food.
Whenever I know that she's coming home I try to prepare, with more-than-the-usual amount of vegetables, a good supply of tofu and soy milk and more-than-the-usual amount of legumes and grains in the menu. I've learned to make eggless challah (pretty easy, actually -- just increase the amount of oil) but it certainly quashes the opportunities for kugels and other baked goods.
This weekend, it's not my worry -- evidently she and her soldier-brother, who is also expected home, have prepared to take responsibility for the Shabbat cooking. My job is to stay out of the kitchen.