Tree nut allergy
|Tree nut allergy|
|Classification and external resources|
Tree nut allergy, a hypersensitivity to dietary substances from tree nuts causing an overreaction of the immune system, may lead to severe physical symptoms. Tree nuts include almonds, Brazil nuts, cashews, chestnuts, filberts/hazelnuts, macadamia nuts, pecans, pistachios, and walnuts.
People with tree nut allergy are seldom allergic to just one type of nut, and are therefore usually advised to avoid all tree nuts, even though an individual may not be allergic to all varieties of tree nuts. Someone allergic to walnuts or pecans may not have an allergy to cashews or pistachios, even though close biological relatives often share related allergenic proteins. The severity of the allergy varies from person to person, and exposure can increase sensitization. For those with a milder form of the allergy, a reaction which makes the throat feel like cotton may occur. The raw nut protein usually causes a more severe reaction than the oil, and extra roasting or processing can reduce the allergic reaction. Those diagnosed with anaphylaxis will have a more immediate mast cell reaction and be required to avoid all exposure to any allergen-containing products or byproducts, regardless of processing, as they are prone to even greater sensitivity. An allergy test or food challenge may be performed at an allergy clinic to determine the exact allergens. New immunotherapy treatments are being developed for tree nut allergy.
Tree nut allergy is distinct from peanut allergy, as peanuts are considered legumes, whereas a tree nut is a hard-shelled fruit of certain plants. Some people are allergic to cashew nuts, but cashews are a less frequent allergen than nuts or peanuts. Pine nuts allergy is also distinct, as they are seeds from a pine tree, although the allergic reaction appears to be similar and some people may have an allergy to both.
This allergy tends to be lifelong; recent studies have shown that only about 9% of children outgrow their tree nut allergy.
Hazelnut has been used as a model tree nut in the study of tree nut allergies.
Prevention and treatment
||The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject. (August 2012)|
In the United States, the federal Food Allergen Labeling and Consumer Protection Act (FALCPA) requires that any packaged food product that contains tree nuts as an ingredient must list the specific tree nut on the label. Foods that almost always contain tree nuts include pesto, marzipan, Nutella, baklava, pralines, nougat, gianduja, and turrón. Other common foods that may contain tree nuts include cereals, crackers, cookies, baked goods, candy, chocolates, energy/granola bars, flavored coffee, frozen desserts, marinades, barbecue sauces, and some cold cuts, such as mortadella. Tree nut oils (especially shea nut) are also sometimes used in lotions and soaps. Asian and African restaurants, ice cream parlors, and bakeries are considered high-risk for people with tree nut allergy due to the common use of nuts and the possibility of cross contamination.
Treatment usually involves an exclusion diet and vigilant avoidance of foods that may be contaminated with tree nuts, nut particles, or oils. The most severe nut allergy reaction is anaphylaxis, an emergency situation requiring immediate attention and treatment with epinephrine.
Tree nut alternatives
Since many people with tree nut allergies also have peanut allergies, and peanut butter is a popular derivative of peanuts and widely used product, especially in the United States, many schools offer peanut-free menu options or implement entirely nut-free policies.  For instance, sunflower seed butter can provide an alternative in schools where peanut butter and peanuts have been banned. However, a small number of people with tree nut and/or peanut allergies may also be allergic to sunflower seed butter. According to one study a person with a known peanut allergy suffered an acute reaction to a "nut-free" butter containing sunflower seeds. 
From a nutritional perspective, sunflower butter contains almost four times as much vitamin E as peanut butter, and about twice as much iron, magnesium, phosphorus and zinc. Peanut butter contains higher levels of protein and slightly less sugar and fat.
- Birmingham NP, Parvataneni S, Hassan HM, et al. (2007). "An adjuvant-free mouse model of tree nut allergy using hazelnut as a model tree nut". Int. Arch. Allergy Immunol. 144 (3): 203–10. doi:10.1159/000103993. PMID 17570928.
- National Institutes of Health, NIAID Allergy Statistics http://www3.niaid.nih.gov/topics/foodAllergy/understanding/quickFacts.htm[dead link]
- National Report of the Expert Panel on Food Allergy Research, NIH-NIAID 2003 http://www3.niaid.nih.gov/about/organization/dait/PDF/june30_2003.pdf
- Groce, Victoria (2008-06-09). "Why is My Child’s School Nut-Free? What food can she bring?". foodallergies.about.com. Retrieved 2011-03-03.
- Hsu, Denise (2007). "Is "nut-free" sunflower seed butter safer for children with peanut allergy?". The Medical Journal of Australia 198 (9): 542–543.
- Thomas, R.G. "Sunflower Seed Butter and Almond Butter as Nutrient-Rich Alternatives to Peanut Butter". USDA. Retrieved 2012-11-12.
- Peabody, Erin (2005-05-17). "Sunflower Seed Butter Improves As It Spreads Across America". USDA. Retrieved 2012-11-12.
- Tree nut allergy at Food Allergy Initiative
- "Are Nut Bans Promoting Hysteria?" by Tana Parker-Pope at The New York Times (15 Dec 2008)
- Is Peanut Allergy Related to Tree Nut Allergies? at PeanutAllergy.com