Prevalence of Tree Nut Allergies
There is a geographical variation in the prevalence of tree nuts which relates the type of nuts consumed in that country. In Australia cashew nut allergy is the most common in infants affecting 0.33% and hazelnut 0.18% and walnut 0.16%, with allergies to Brazil are almond being rarely seen (1). In the USA tree nut allergy has been reported to be increasing with walnut, almond and pecan being the most common (1). In the UK the most common tree nut allergies are to Brazil, almond and hazelnut (1). Cashew nut allergy appears to display a similar clinical history to peanut allergy including wheezing and even anaphylaxis (1). Oral Allergy Syndrome (OAS) is also seen with hazelnuts, hence the importance of the true diagnosis of nut allergy (1). With tree nut allergy, it is estimated that only 9% of allergies are outgrown with cashew nut allergy rarely being outgrown (1).
Foods and Allergens
Tree nuts include cashew, almond, Brazil, hazelnut, chestnut, pistachio, pecan, walnut, macadamia nut, pinenut and coconut (1). As with legumes it is the plant food superfamily classification of the allergens in tree nut allergy which are of importance (1).
Studies have shown a strong clinical cross reactivity between tree nuts and peanuts within allergic individuals. In the general population the risk of having both is 2.5 %. The risk is considerably higher in atopic individuals and studies have estimated this to be 23 ? 50 %.
Oral Allergy Syndrome can also be triggered by tree nuts, with the most common cross reactivity occurrs between allergens from almonds, hazelnuts, and walnuts and the antibodies to the main birch pollen allergens (1). A similar cross reactivity can also occur between latex and some tree nuts (1).
Diagnosis of Tree Nut Allergy
Skin prick tests and specific Ig E tests in conjunction with a good clinical history are keys to the diagnosis of tree nut allergy. When these results are contradictory then a medically supervised oral food challenge is required for diagnosis (1).
At present the only effective and proven management of any tree nut allergy is the total avoidance of the offending allergen (1).
Table: alternative name for nuts and foods likely to contain nuts
|Hazelnut||Filbert, cob nut|
|Macadamia||Queensland nut, candle nut|
|Spreads||Chocolate Hazelnut Spread|
|Snacks & Sweets||Cereal bars, mixed nuts, praline, nougat, Turkish Delight, marzipan|
|Cakes & Biscuits||Cookies, brownies, fruit cake, anything with marzipan, almon croissants|
|Ice Creams||Nut toppings, pistachio ice cream, kulfi|
|Vegetarian Meals||Nut Roast, Veggie Burgers|
|Sauces||Almond essence, nut oils|
1. Tanya Wright and Rosan Meyer., Dietary Management of Milk and Eggs -Food Hypersensitivity: diagnosing and managing food allergies and intolerances ? edited by Isabel Skypala, Carina Venter; Wiley and Blackwell 2009, Part 2, p 117- 128.
2. Consumer Information: Information for Allergy Suffers: Food Standards Australia New Zealand, April 2010. www.foodstandards.gov.au
by Julie Albrecht Consultant Dietitian-Nutritionist A.P.D.