An estimated 1.8 million Americans (between 0.4%-0.6% of the population) have an allergy to tree nuts. About 35-50% of peanut allergic patients can also be allergic to at least one tree nut. In culinary terms, these foods are called nuts, but botanically they are seeds.
The most common nut allergies are:
- Walnut: 34% of all nut reactions. The Persian or English walnut (Juglans regia) is a nutrient-dense food with 15.2 grams of protein per 100 grams of walnut and high in Vitamin C. The proteins responsible for walnut allergy are lipid transfer protein (LTP) and vicilin. Walnuts have potential cross-reactivity with other foods including pecan, peanut, mustard and peach. The black walnut although very flavorful is not grown commercially for nut production due to poor hulling characteristics. The U.S. is second only to China in the production of walnuts. There are many health claims from eating walnuts including antioxidant effects that protect against heart disease and a 2012 study showed that eating walnuts improved sperm quality in healthy young men. Even if a person is allergic to walnut tree pollen, they are unlikely to have walnut food allergy.
- Cashew: 20% of all nut reactions and known for causing anaphylaxis in children. About 7.4 mg of protein will trigger an allergic reaction. There are 18.2 g of protein per 100 g (3.5 oz) of cashews. Also known as Anacardium occidentale, cashews are native to Northeastern Brazil. Nigeria and India were the top producers of cashews in 2010. Many patients with cashew allergy will also react to pistachios. Some patients with birch pollen allergy will develop itchy mouth with eating cashews; this is called Pollen-Food Allergy Syndrome, formerly known as Oral Allergy Syndrome. In Sweden, cashew allergy was found to be as common as milk and egg allergy in children less than 3 years old and leading to severe allergic reactions requiring treatment in the ER.
- Almond: 15% of all nut reactions. Prunus dulcis is the genus and species and there are currently 8 groups of allergenic proteins identified. Cross reactivity with peaches, apricot and cherries is common due to a shared LTP (lipid transfer protein). The seed contains 21.2 grams of protein per 100 grams of almonds. The U.S. is the top producer of almonds in the world and nearly all are produced in California. Commercially grown almonds are the sweet variety, while extracts of “bitter almonds” contain cyanide and can be deadly!
- Pecan: 9% of all nut reactions. Pecans are native to the southcentral U.S. and are from the pecan tree which is closely related to hickory trees. The major allergens from this seed called Carya illinoinensis have not been fully identified but they share proteins with walnut, increasing the risk of symptoms in walnut-allergic patients. There are 9.17 grams of protein per 100 g of pecans. Pecans have been shown to lower the risk of gall stones in women and potentially improve high cholesterol through anti-oxidant effects. Fatal pecan anaphylaxis has been reported.
While tree nut allergy is typically life long, about 9% of individuals will outgrow their nut allergy especially if the reaction was mild. The reactions can be mild to severe including life-threatening anaphylaxis in children and adults. For unclear reasons, the prevalence of tree nut allergy appears to be rising.
At Family Allergy & Asthma Care of Montana, we are nuts about diagnosing and treating food allergies! We can identify the specific nut and develop an individualized treatment plan for you.
As an ACE (Anaphylaxis Community Expert), my team will provide informational seminars to school, health or community groups in Southwestern Montana free of charge. Call our office at 406-451-7017. For an ACE expert in your community go to: http://www.aanma.org/2010/12/find-an-anaphylaxis-community-expert-ace/
This information is solely for informational purposes and not intended as a substitute for consultation with a medical professional.