Tree nut allergy is usually lifelong and together with peanut allergy are the most common cause of food induced anaphylaxis. There is not as much data compared to peanut allergy.
Children with peanut allergy are thought to be at increased risk of tree nut allergies, with around 30% of pediatric patients presenting with peanut allergy reported to have allergies to tree nuts.
In a recent study published in the Journal of Allergy and Clinical Immunology, researchers sought to estimate the population prevalence of tree nut allergy during the first 6 years of life.
- Tree nut allergy affected 3.3% of 6 year olds, with cashew being the most common, followed by pistachio, hazelnut, walnut and almond. Of note, peanut is not a tree nut, but a legume.
- At 1 year of age, 41% of those with egg or peanut allergy were already sensitized to 1 or more tree nuts. At age 6 years, almost half developed tree nut allergy.
The authors who were based in Australia, noted high regional variation of the type of nut allergy. In Europe, studies report hazelnut as the most common nut allergy. This is largely based on the high rate of birch pollen allergy and its cross reactivity to hazelnut. In the UK, Brazil nut was reported as the most common tree nut allergy. In the U.S., walnut and cashew were reported as the most common.
Conclusion: Tree nut allergy is uncommon in the first year of life, likely because of limited tree nut consumption. At age 6 years, its prevalence is similar to peanut allergy prevalence. More than a third of children with both peanut and egg allergy in infancy have tree nut allergy at 6 years.
A big breakthrough in peanut allergy has been the study which showed the early introduction of it decreased the development of allergy.
If the data from the peanut study is inferred, the early introduction of tree nuts may also decrease allergy. Tree nuts are a choking hazard to children, so it may be more advisable to given in the form of cashew or almond butter for example. More understanding in how to prevent tree nut allergy should be an urgent priority for future research.