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Peanut allergy

Peanut allergy is one of the most common food allergies. It is caused by a combination of genetic and environmental risk factors.

Characteristics of Peanut allergy
A peanut allergy is a type of food allergy. Peanuts are a type of legume (e.g., beans, peas, lentils, and soybeans) and are not the same as tree nuts (e.g., almonds, cashews, walnuts, and others). Peanut allergy occurs when the body’s immune system (i.e., the system that helps the body protect itself from disease) mistakes a protein found in peanuts for an allergen (something that causes an allergy) and attacks it. When this happens, an unusually large amount of an infection-fighting cell called immunoglobulin E, IgE, is produced to fight that protein. This is what causes symptoms of an allergic reaction.
Signs and symptoms of a peanut allergy can range from mild to potentially fatal. Mild symptoms include an itchy mouth or ears, nausea or vomiting, diarrhea, stomach pain, or more traditional allergic reactions, such as nasal congestion, sneezing, or a dry cough. Severe symptoms (anaphylaxis) include obstructive swelling of lips, tongue, or throat, shortness of breath, chest pain, and drop in blood pressure.

Diagnosis/Testing
Peanut allergy may be diagnosed after a review of an individual’s medical history, physical exam, and results from blood tests, oral food challenges and/or a trial elimination diet. There are many factors that influence an individual’s risk of developing peanut allergy. Changes or variants in certain genes, such as variants in the FLG gene, are known risk factors for peanut allergy. Variants in the FLG gene are known to convey strong risk factors for other allergy conditions such as hay fever (allergic rhinitis), asthma, and eczema (atopic dermatitis). While there is a significant genetic influence on peanut allergy, it is important to know that not all individuals with a variant in the FLG gene develop an allergy to peanuts.

Management/Surveillance
Since peanut allergy symptoms may be very severe and can be triggered by eating very small amounts of peanuts, or by being exposed to peanuts, it is very important for individuals with a peanut allergy to avoid peanuts. It is recommended that individuals with a peanut allergy have an epinephrine auto-injector, such as an EpiPen. This can temporarily reduce an allergic reaction to peanuts in case they are accidentally consumed. Some people with milder allergies can manage symptoms with antihistamines.
It is important to be vigilant about the ingredients in all foods , both while shopping for food and especially while eating out. Often, people with peanut allergy avoid all nuts in general as nuts are often processed together and may be contaminated. Although peanut allergy is generally a lifelong condition, some studies show that about 20% of children with peanut allergy may outgrow their allergy.

Mode of inheritance
Peanut allergy is a complex condition, which means that it is caused by a combination of many different factors. These factors can be genetic or non-genetic (such as environmental factors). Complex conditions are inherited in a multifactorial pattern. This means that the chance for an individual to develop a peanut allergy is influenced by the number and type of genetic and non-genetic factors that occur together to which an individual is exposed. In other words, no single gene, and no single environmental factor cause a peanut allergy. However, not all of these genetic factors and environmental factors are known.

Risk to family members
Siblings of individuals who are allergic to peanuts may be at an increased risk for peanut allergy.

Special considerations
None

Resources
Food Allergy Research & Education
Learning Early About Peanut Allergy
Anaphylaxis Campaign – Peanut allergy fact sheet
Peanut Institute – Peanut allergy white paper

References
Brown, SJ. et al. (2011)."Loss-of-function variants in the filaggrin gene are a significant risk factor for peanut allergy." Journal of Allergy and Clinical Immunology 127(3-4): 661-667.
Skolnick, HS, et al. (2001)."The natural history of peanut allergy." Journal of Allergy and Clinical Immunology 107(2): 367-74.
Smith, FJD. et al. (2006)."Loss-of-function mutations in the gene encoding filaggrin cause ichthyosis vulgaris." Nature Genetics 38(3): 337-342.

Created:04/2014

Updated:mm/yyyy

Created by:Aditi Shankar, BA, Seema Jamal, MSc, LCGC

Edited by:Karin Dent, MS, LCGC



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