Cashew nut allergy is on the rise, Ana o 3 IgE seems to be the best single test to diagnose cashew allergy. Cashew nut belongs to the Anacardiaceae family, along with pistachio nut and mango. Cashew and pistachio nut cross-react both in IgE testing and clinically. Cashew nut is typically consumed as a snack and it is used in many Asian cuisines, its also used in ice cream and chocolates.
Cashew nut is a potent allergen, less than 1 mg of protein can cause allergic symptoms in cashew allergic children. Even 0.3 mg has caused mild transient objective symptoms. Skin or mucosal contact only can cause anaphylaxis in some patients.
Component testing can help aid in the diagnosis along with skin prick tests and specific IgE tests. Sensitization to 2S albumin of cashew nut (Ana o 3) seems to be an accurate predictor for a positive cashew nut challenge outcome.
A recent study published in the Annals of Allergy, Asthma and Immunology, titled “Optimizing tools for evaluating challenge outcomes in children with cashew allergy”, aimed to predict which patients with a positive Ana o 3 to cashew would react to a cashew nut allergy challenge.
68% of the patients reacted who underwent the challenge, reacted to cashews. Ana o 3 IgE seemed to be the best single test to diagnose cashew allergy, with 0.97 kU/L cutoff exhibiting 94% specificity and 61% sensitivity . However the authors concluded that cut off values may be age specific in predicting food challenge outcomes.
If there is question of cashew allergy, the tests your allergist can perform are skin prick testing to cashew, total IgE test to cashew, and in this study the specific component Ana o 3 to cashew. A positive skin or lab test does not necessarily mean one is allergic to cashews, as testing can have false positives and false negatives as well. Based on their study, they conclude that a value of greater than 0.97 kU/L of Ana o 3 IgE testing, there is a high likelihood of a positive food allergy to cashew.