Take care when cooking.
If everyone in the household isn't following an allergen-free diet, you want to be sure to avoid cross-contamination.
It's a good idea to have two sets of cooking and eating utensils — one exclusively for the allergic person — so that a knife used to cut a peanut butter sandwich isn't inadvertently used to butter the toast of someone who's allergic to peanuts.
All dishes and utensils should be thoroughly washed in hot, soapy water between uses.