My allergist has an anecdote about a patient, a middle aged male, who had a
severe peanut allergy.  One of his nurses, who was pregnant, had a pica
(sp?) for peanut butter.  This nurse was attending this patient, and
greeted him with "Hello, Mr. ____, and how are you today?"  The peanut
fumes on her breath were enough to make him break out into hives!  Peanut
allergies are nothing to fool around with.

The most common food allergy (in the USA) is milk.  What is not as well
known is that the second most common allergy is soy.  People tend to think
soy is a very safe food.  Sensitization may be slow; the reactions aren't
always dramatic.
Susan Betz