Q. My child's school sent a note that some kids in the class have a peanut allergy. When I bring food for a party, should I make sure there are no nuts in it?

A. If only it were that simple. Peanuts show up in places you wouldn't expect. Nuts are often blended into cereals, granola bars, and baking mixes. Many soups use nuts as thickeners, and a variety of foods are made with peanut oil. And many foods without nuts are processed on machines where peanut-containing foods were made, which can cause a reaction in an allergic person. Even plain M&M's can have traces of them, for instance (as can lots of other chocolate candies).

The best thing to do: Read labels carefully on any treat for the class, even things you wouldn't imagine have peanuts in them. Because of the increase in the incidence of peanut allergies, most foods will have a warning if they do contain nuts or if they're processed on machines that also manufacture other foods that contain them.

This can be a nuisance (I once spent 15 minutes in the grocery store looking for a snack to send to my daughter Elsa's peanut-free classroom; I normally would've grabbed something in 30 seconds). But it needs to be taken seriously because the allergic reaction can be life-threatening. On PopSci.com: Why are so many kids allergic to peanuts?

Many preschools have peanut-free tables in the lunchroom (so there's no possibility of kids trading food or getting peanut butter on their fingers from a neighbor's lunch) or peanut-free classes like Elsa's, where even her own snacks couldn't contain them. Check the school's policy and consider asking the parents of the child who's allergic (if that information's available to you) for ideas for safe snacks.