Single nut or total nut avoidance in nut allergic children: outcome of nut challenges to guide exclusion diets

Children with diagnosed nut allergy are typically advised by health professionals to exclude all nuts from their diets, irrespective of the outcome of allergy testing, to avoid inadvertent contact through contamination or the possible development of new allergies.

In our service, as we feel greater diagnostic accuracy prevents dietary risk taking, we provide the facility for children with nut allergy the opportunity of controlled exposure to 'other' nuts irrespective of whether their allergy prick test (PT) results are positive or negative. We performed open food challenges on our paediatric day ward. The challenge food was administered by way of a homemade biscuit containing 8 g of each nut challenged and given in increasing visually measured doses.

Over the 5-year period from 2006, we challenged 145 children diagnosed as peanut allergic or tree nut allergic. In those with peanut allergy challenged to tree nuts, none of the 72 with negative PTs to tree nuts reacted on challenge whilst 7 of 22 (31.2%) with positive PTs did. In patients with tree nut allergy challenged to peanuts and/or other tree nuts, 3 of 38 (7.9%) with negative PT results and 5 of 13 (38.4%) with positive PT results reacted.

Children allergic to peanuts with negative allergy tests to tree nuts had no co-existing allergy, but were at risk of tree nut allergy where PTs were positive. Children with tree nut allergy were at risk of co-existing peanut or other tree nut allergy whether PTs were positive or negative. Oral challenges to clarify allergy status in all nuts show co-existing allergies even in young children and in so doing may reduce anxiety, minimize unnecessary dietary restrictions and prevent later episodes of anaphylaxis through uninformed exposure.