Peanut
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According to a study funded by Food Allergy Research and Education, the number of children in America with peanut allergies more than tripled between 1997 and 2008. Since the report, some schools have banned peanut products from their campuses. Peanut allergies usually last a lifetime and people with them are often also allergic to tree nuts. Because the two tend to come into contact during manufacturing and serving, people with peanut allergies are advised to steer clear of tree nuts as well.