Tree nuts are one of the most common foods causing acute
allergic reactions and nearly all tree nuts have been associated with fatal
allergic reactions. Despite their clinical importance,
tree nut allergy epidemiology remains understudied and the prevalence of
tree nut allergy in different regions of the world has not yet been well characterised. We aimed to systematically review the population prevalence of
tree nut allergy in children and adults. We searched three electronic databases (OVID MEDLINE, EMBASE and PubMed) from January 1996 to December 2014. Eligible studies were categorised by age, region and method of assessment of
tree nut allergy. Of the 36 studies identified most were in children (n = 24) and from Europe (n = 18), UK (n = 8) or USA (n = 5). Challenge-confirmed
IgE-mediated
tree nut allergy prevalence was less than 2 % (although only seven studies used this gold standard) while probable
tree nut allergy prevalence ranged from 0.05 to 4.9 %. Prevalence estimates that included oral
allergy syndrome (OAS) reactions to tree nut were significantly higher (8-11.4 %) and were predominantly from Europe. Prevalence of individual
tree nut allergies varied significantly by region with hazelnut the most common
tree nut allergy in Europe, walnut and cashew in the USA and Brazil nut, almond and walnut most commonly reported in the UK. Monitoring time trends of
tree nut allergy prevalence (both overall and by individual nuts) as well as the prevalence of OAS should be considered given the context of the overall recent rise in
IgE-mediated
food allergy prevalence in the developed world.