Tree nut allergy (TNA) is an immune system reaction to proteins found in nuts that grow on trees, such as almonds, walnuts, cashews, and pecans. These are distinct from peanuts, which are legumes. TNA is one of the most common food allergies. Reactions range from mild symptoms like hives to severe, life-threatening anaphylaxis. Because tree nuts are pervasive in the modern food supply, understanding the scope of this allergy is a major focus of current research.
Current Prevalence Rates
Tree nut allergy is the second or third most common food allergy, depending on the population studied. The estimated prevalence of TNA in the United States is approximately 1% to 1.2%. Worldwide estimates range more broadly, from 0.05% to nearly 5%.
Surveys often rely on self-reporting, which can lead to an overestimation of the true prevalence. When diagnosis is confirmed by a physician using objective measures like the oral food challenge, the prevalence rate is lower, often less than 2%.
However, self-reported rates still represent a large number of people managing a perceived or diagnosed allergy daily. Tree nut allergies are frequently cited as a leading cause of severe allergic reactions requiring emergency medical attention.
Changing Trends in Tree Nut Allergy
Epidemiological data suggest that the prevalence of tree nut allergy has been increasing over the past few decades, particularly in industrialized nations. In the United States, the self-reported rate among children rose substantially from 0.2% in 1997 to 1.1% in 2008. This rise is a consistent trend across multiple studies and contributes to the overall increase of food allergies.
The observed rise may be partly explained by better public awareness and improved diagnostic testing. However, the scale of the increase suggests that genuine environmental or lifestyle factors also play a role. Theories involve changes in dietary habits, such as the timing of nut introduction in infancy, or environmental shifts affecting the immune system (the hygiene hypothesis).
This upward trend represents a growing challenge for schools, food manufacturers, and public health systems. The increase highlights the need for ongoing research into the underlying causes of food allergy development.
Prevalence Differences Among Specific Nuts and Age Groups
The term “tree nut allergy” encompasses a variety of distinct allergies, and prevalence varies considerably by geography. Walnut and cashew are often the most commonly reported allergies in the United States. Conversely, hazelnut is frequently the most common tree nut allergy across Europe.
It is possible to be allergic to only one type of tree nut, but many individuals with one TNA are also allergic to others. Cross-reactivity is common between pairs like cashew and pistachio, and walnut and pecan, due to shared protein structures. Allergists generally advise patients to avoid all tree nuts to prevent accidental exposure and the likelihood of developing additional sensitivities.
TNA is typically diagnosed in childhood and is largely considered a lifelong condition. Only about 10% of children will outgrow their sensitivity. Tree nut allergies account for a large proportion of the IgE-mediated reactions seen in teenagers and adults.