Tree nut allergy

Did You Know?

• Tree nut seed storage proteins are the allergens responsible for severe tree nut allergic reactions.
• Storage proteins include the prolamin superfamily and the cupin superfamily, with additional pan-allergens such as lipid transfer proteins, profilins, pathogenesis-related proteins, and heveins.
• Children with tree nut allergies may develop allergic rhinitis, asthma, or atopic dermatitis later in life.

Signs and symptoms

Food allergies generally have symptom onset within minutes to hours for an immunoglobulin E (IgE)-mediated response, which may include anaphylaxis. Symptoms can include rash, hives, itching of the mouth, lips, tongue, throat, eyes, skin, or other areas; swelling of lips, tongue, eyelids, or the whole face; difficulty swallowing; runny or congested nose; hoarse voice; wheezing; shortness of breath; diarrhea; abdominal pain; lightheadedness; fainting; nausea; or vomiting. Non-IgE-mediated responses occur hours to days after consumption and are less severe. Anaphylactic onset is characterized by respiratory distress, such as wheezing and breathing difficulty, along with circulatory impairment like weak pulse, pale skin, and fainting. Untreated, this can lead to anaphylactic shock. Consumption of raw nuts usually causes a more severe reaction than roasted nuts or food-grade nut oils.

Diagnosis

An allergy test or food challenge may be performed at an allergy clinic to determine the exact allergens involved and guide safe treatment or management. People who suspect allergic reactions to any tree nut should be tested by an allergist immediately, as the condition can be life-threatening. Tree nut allergies can be genetic. Skin-prick tests and blood tests measure immunoglobulin E (IgE) to determine if an allergy is present. If results are inconclusive, an oral food challenge may be used as a final determining factor, where the patient consumes tiny amounts of the suspected food under direct supervision, but only when the probability of passing is high.

Prevention

Managing a tree nut allergy means strictly avoiding foods that might contain nuts, nut pieces, or nut oils. In the U.S., the Food Allergen Labeling and Consumer Protection Act requires packaged foods to name the specific tree nut if it's an ingredient. Certain foods almost always contain tree nuts, such as pesto, marzipan, Nutella, baklava, pralines, nougat, gianduja, and turrón. Other items that may include them are cereals, crackers, cookies, baked goods, candy, chocolates, energy bars, flavored coffee, frozen desserts, marinades, barbecue sauces, and some cold cuts like mortadella.

Tree nut oils, especially shea nut, also appear in lotions and soaps. High-risk dining spots include Asian and African restaurants, ice cream parlors, and bakeries, due to frequent nut use and cross-contamination. Someone allergic to one tree nut can react to others, including peanuts (which are legumes). About one-third of people with a confirmed allergy react to more than one type.

Cross-reactivity is stronger among almond, walnut, pecan, hazelnut, and Brazil nut than toward cashew or pistachio. Because allergies to a single nut are rare, doctors often advise avoiding all tree nuts. However, someone allergic to walnuts or pecans may not react to cashews or pistachios, as these groups are distantly related.

Regulation

Food allergy awareness has increased, impacting quality of life for children, parents, and caregivers. In the United States, the Food Allergen Labeling and Consumer Protection Act, enacted in August 2004 and effective January 1, 2006, requires companies to disclose on labels whether a packaged food product intentionally contains any of eight major allergens: cow's milk, peanuts, eggs, shellfish, fish, tree nuts, soy, and wheat. This list originated from the World Health Organisation Codex Alimentarius Commission in 1999.

Ingredients derived from these allergens must have their food source name in parentheses or a separate statement like 'Contains milk.' The European Union requires listing for those eight plus molluscs, celery, mustard, lupin, sesame, and sulfites. No labeling laws mandatorily declare trace amounts from cross-contamination, except in Brazil. Restaurants have added allergen warnings to menus, and the Culinary Institute of America offers courses in allergen-free cooking.