New study reveals rising cashew nut allergy in children and unexpected almond allergy risk in adults

A new study using data from the European Anaphylaxis Registry has identified important changes in which tree nuts are most likely to cause serious allergic reactions (anaphylaxis) in children and adults across Europe. The results show that cashew nuts are now a leading cause of anaphylaxis in children, and that almonds are an unexpected risk for adults.

Why was this study carried out?

Food allergies are a growing health concern, and tree nuts—like hazelnuts, almonds, walnuts, pecans, cashews, pistachios, Brazil nuts, and macadamia nuts—are among the most common triggers for anaphylaxis. As diets and lifestyles change, with some foods becoming more popular, researchers wanted to find out if the types of tree nuts causing serious reactions are changing, and whether this is different for children and adults.

What did the researchers do?

The team analysed reports from the European Anaphylaxis Registry, a database that collects information on serious allergic reactions from across Europe. They focused on cases from 2007 to April 2024 where tree nuts were the cause. Out of nearly 6,000 food-related anaphylaxis cases, 1,389 (over 1 in 5) were due to tree nuts. The researchers looked closely at 1,083 cases where the specific nut was confirmed, to see which nuts were causing the most problems.

What did the study find?

• Cashew nuts are now the most common cause of tree nut anaphylaxis in children. Most children affected were very young (average age 4), and almost all (97%) of the cashew cases were in children. Worryingly, most children and adults who reacted didn’t know they were allergic beforehand.
• Reactions to cashew nuts can happen with tiny amounts of the nut. Many children reacted to less than a teaspoon of cashew, and some even had allergic symptoms after skin or mouth contact. This suggests that cashew allergy can cause serious reactions at even lower amounts than peanut allergy.
• Cashew allergy is on the rise. Cases of cashew-induced anaphylaxis have increased steadily, likely because cashew is now more common in snacks, vegan foods, and sauces like pesto.
• Cashew and pistachio allergies often occur together. This is because the proteins in these nuts are very similar, so people allergic to one are often allergic to the other as well. However, stomach symptoms occurred more frequently in cases of anaphylaxis caused by cashews.                                                         
• Almonds are an unexpected risk for adults. While hazelnuts and walnuts remain the top triggers in adults, the study found a surprising number of almond-induced anaphylaxis cases, especially in countries like Italy. This may be linked to specific allergy types (such as Lipid Transfer Protein (LTP) allergies) that are more common in southern Europe.
• Most people weren’t aware of their allergy. Only about 1 in 5 patients, including children and adults, were aware they had a nut allergy before their reaction.
• Cofactors can make reactions worse. Cofactors like exercise, alcohol, asthma or certain medicines can make allergic reactions more serious. These were seen in half of adult cases but only 17% of children.
• Emergency treatment needs improvement. The use of adrenaline (the recommended emergency treatment for anaphylaxis) was low, particularly outside of hospital. Only 13% of children and just 3% of adults received adrenaline from bystanders or family before getting professional help, even though it can save lives.

What does this mean?

These findings show that the risks from tree nut allergies are changing. Cashew allergies are becoming a bigger problem for children, and almonds are a more significant risk for adults than previously thought. Because most people don’t know they’re allergic until their first serious reaction, it’s vital that schools, families, restaurants, and the public are allergy-aware and know how and when to respond in an emergency, including how to use adrenaline auto-injectors.

At present, there are no approved treatments like oral immunotherapy (OIT) for cashew or other tree nut allergies on the NHS, though research is ongoing and looks promising. For now, managing nut allergies means avoiding the nuts, being prepared for emergencies, and knowing that factors like asthma, exercise, certain medicines, or alcohol can make reactions worse. Healthcare professionals should also continue to check for cashew and almond allergies when assessing patients with suspected nut allergies. Continued research and better education are essential to help protect people at risk and support the development of new treatments.

Read the full article here: A Growing Concern for Cashew and an Unexpected Risk From Almonds: Data From the Anaphylaxis Registry