Specific immunoglobulin E to peanut, hazelnut and Brazil nut in 731 patients: similar patterns found at all ages

Background Previous studies have reported reactions to an increasing range of nuts as patients with nut allergy grow older. Most patients with symptom s suggesting nut allergy have specific IgE to more than one nut. Furthermor e, fatal reactions have followed eating nuts different from any causing the deceased's previous reactions. Objective To explore the pattern of specific IgE to three distantly related nuts in patients of all ages with nut allergy. Methods This study includes all patients referred to our laboratory for nut allergy testing from January 1994 to August 1998 who were tested for peanu t, hazelnut and brazil nut, and had specific IgE to at least one of these n uts. All tests were performed using the Pharmacia Unicap system. Results Seven hundred and thirty-one patients (age 7 months to 65 years, me dian 6.6 years) had specific IgE > 0.35 kU(A)/L to at least one of these th ree nuts: 282 had IgE to one nut, 130 to two nuts, and 319 to all three nut s. When analysed by gender and age quartile, very similar patterns were fou nd in all subgroups though significant age trends and age interactions were found for IgE to individual nuts and combinations of nuts. Conclusions The probability of a patient with nut allergy having specific I gE to a particular combination of peanut, hazelnut and brazil nut is simila r, whatever their age or sex. The apparent increase in multiple nut reactiv ity with increasing age may therefore be due to exposure of previously unch allenged sensitivity. The frequency of multiple-nut specificity is sufficie ntly high that patients should always be tested for allergy to a range on n uts if they have a history of reacting to any nut.