More and more children are allergic to cashew nuts
Nuts account for around a quarter of all food allergies. Recently, cashew nuts have been causing a particularly high number of severe reactions in children. This is probably because of increased consumption.
Whether as a savoury snack or disguised in gluten-free flour and vegan milk, cashew nuts, which originally come from Brazil, are very much in demand. They are rich in protein but contain less fat and calories than other nuts. Incidentally, cashews are not actually nuts, but the kernels of a fruit.
However, their growing popularity is also reflected in a recently published study on nut allergies. The analysis of the European Anaphylaxis Registry revealed a noticeable increase in severe allergic reactions to cashews in young children.
One hundred and forty-two allergy centres from various countries regularly report their anaphylaxis cases to the registry. These are strong reactions of the immune system to certain triggers such as food, medication or insect venom. They can cause rashes, swelling and difficulty breathing, and in severe cases also anaphylactic shock, which can potentially cause the entire cardiovascular system to fail. In rare cases, this can be fatal.
Skin contact can be all it takes
An international research team has now analysed all recorded cases of anaphylaxis triggered by food between 2007 and 2024. The team found that of the almost 6,000 cases, just under a quarter were triggered by nuts that grow on trees, such as walnuts, almonds and hazelnuts. This category does not include peanuts, which grow underground, but are also frequently associated with severe anaphylaxis in children.
Karin Hartmann, whose research into allergic diseases is funded by the SNSF, was involved in the study. Hartmann is Head of the Division of Allergy and Deputy Chair of the Department of Dermatology at the University Hospital Basel. She is also Research Group Leader at the Department of Clinical Research and the Department of Biomedicine at the University Hospital Basel and University of Basel.
The researchers of the European Anaphylaxis Registry took a closer look at around 1,000 well-documented cases of these nut allergies. "The registry enables us to compile a large number of cases, even for less common allergies. This gives us enough data to examine subgroups such as adults and children separately," says Hartmann.
The most surprising result? In over 40% of cases involving children under the age of five, cashew nuts were responsible for the anaphylactic reaction. One in three of these children reacted to small amounts of less than a teaspoon of cashews. In a handful of cases, even skin contact or inhalation was enough to trigger a reaction.
Cashews overtake native nuts
Until now, research into severe allergic reactions to tree nuts has focused on native species such as hazelnuts and walnuts. These are now in second and third place among children. The increase in cashew allergies is most likely due to their increased consumption in recent decades. Cashews are often disguised in products such as pesto or deliberately used as a vegan source of protein.
"As a result, many more children are coming into contact with cashew nuts at an early age compared to the past," says Hartmann. As with many nut allergies, the trigger is a storage protein found in large quantities.
Previous studies confirm that children’s immune systems react particularly violently to this protein found in cashews. Anaphylaxis is even more common than with peanut allergies. And even smaller amounts than with peanuts can trigger a seizure.
In adults, on the other hand, allergies to cashews hardly appeared in the cases documented by the Anaphylaxis Registry. The mature immune system is obviously less susceptible to them. The most common triggers here were hazelnuts – responsible for over 40 percent of cases – followed by walnuts and almonds.
Making adrenaline injections more accessible
However, children should not generally be kept away from cashews out of fear of an anaphylactic reaction, according to Hartmann. "From a nutritional point of view, nuts are a valuable and nutritious food." Less than one percent of the European population develops an allergy to tree nuts. And only a fraction of them experience strong reactions such as anaphylaxis.
If a nut allergy is suspected, Hartmann advises medical consultation. Specialists can determine what types and quantities of nuts cause a reaction and provide personalised advice on how to cope with them. It is not advisable for parents to attempt to put together a nutrition plan for their children without medical counsel as it can potentially lead to nutritional deficiencies. In severe cases, immunotherapy can sometimes be an option. In this process, the body is gradually exposed to increasing doses of the allergy-triggering protein under supervision.
If anaphylactic shock does occur, the rapid administration of adrenaline auto-injectors is crucial. The study results indicate room for improvement here: Less than half of the people who already had a prescription for an adrenaline auto-injector actually used one in an emergency. The study was unable to determine the reasons why, but the fear of giving an injection among people with no medical training may play a role.
However, a remedy for this will soon be made available. Hartmann shared that an adrenaline nasal spray is about to be launched on the market that, according to studies, is just as effective. This could lower the inhibition threshold for use and make nut allergies less frightening.