What is tree nut allergy?
A nut allergy means the immune system mistakenly thinks the protein in nuts is harmful and commences an allergic reaction in an attempt to protect the body from the ‘invader’24. Nut allergy requires specialist medical diagnosis and treatment because allergic reactions can be serious and life-threatening. Consultation with an Immunologist and an Accredited Practising Dietitian who specialises in food allergy is recommended.
The only treatment for food allergy is avoidance
If a person is allergic to a nut, or any other food, they must avoid eating it. Even tiny amounts can trigger a reaction that can be life-threatening. For those with a nut allergy, it is not uncommon to be allergic to several types of nuts, but it is also possible to be allergic to only one type of nut and be able to eat other nuts without any problem.
How common is tree nut allergy?
Tree nuts include almonds, Brazil nuts, cashews, chestnuts, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts.
Australia has often been called the ‘allergy capital of the world’25 and tree nut allergy is one of the most common food allergies in children and adults26. Estimates of nut allergy prevalence, particularly for tree nuts, are limited. The most reliable Australian data comes from studies in children, where peanut allergy affects about 3% and tree nut allergy just under 3%27. Among Australian children, peanut, cashew, and hazelnut are the most common nut allergens.
Macadamia allergy appears to be relatively uncommon, accounting for fewer than 5% of tree nut allergies in some estimates28,29. However, more research is needed to confirm this30.
While most children (but not all) will outgrow food allergies to allergens like eggs or milk, nut allergies tend to persist into adulthood24.
The worldwide prevalence of tree nut allergy varies from between 0.05% to around 5%31,32,33. Interestingly, individual tree nut allergy also varies by region. For example, Brazil nut allergy is particularly common in the UK, almonds and cashews are the predominant tree nut allergens in the US, and hazelnut allergy is most common in Europe31.
Nut allergy symptoms
The symptoms of food allergy usually occur immediately after the food is eaten and can include itching, swelling, hives, wheezing, shortness of breath, sweating, light headedness, nausea and bowel upset. In severe cases the allergic reaction can cause anaphylaxis (swelling of the throat that restricts the ability to breathe) and a sudden drop in blood pressure that can lead to organ failure. If untreated this can be fatal.
People with anaphylactic reactions to nuts are advised to carry an injector pen with a dose of adrenalin (also called epinephrine) to help them survive accidental nut ingestion, however immediate medical attention must be sought as well. They also need to be vigilant in reading food labels and ask questions at restaurants and cafes to avoid nuts in food.
Peanuts are not tree nuts
Peanuts are ground nuts not tree nuts and are classified as legumes. However, peanuts are often bundled together with tree nuts in information about nut allergy as they cause similar reactions. Peanut allergy is more common than tree nut allergy although both, including macadamia allergy, can cause severe reactions or anaphylaxis.
Allergy to peanuts and tree nuts is increasing and no one is sure why. The only modifiable risk factor that’s been identified so far is the timely and ongoing ingestion of allergens (particularly peanut). In other words, introducing nuts, such as nut pastes, early in life (in the first 12 months) and maintaining ongoing intake after that34.
Avoiding nuts
Common allergens such as nuts must be declared on food labels so people with nut allergy can avoid them. If the label is unclear, people with a nut allergy may need to check with the manufacturer. Families with a nut-allergic child are advised to avoid nuts at home to minimise accidental exposure. Beware of nut allergies when preparing and serving nuts, or food containing nuts, to children you don’t know (such as when your children’s friends come to visit or if you host a party).
Nuts in schools and childcare
Individual schools and childcare centres with nut-allergic children can request all children avoid bringing nuts in their lunchbox to avoid the allergic child accidentally eating nuts. However, Australia’s National Allergy Council recommends an ‘allergy aware’ approach, rather than banning specific food allergens, including tree nuts, in schools35. Schools need Allergy Aware policies with guidance for all students. Children allergic to nuts need to learn the dangers of swapping food with friends, and their friends need to be taught not to do this in order to protect their allergic mate. The Allergy and Anaphylaxis Australia Be a Mate program is a good example of this.
Nuts during pregnancy
There is no evidence that women need to avoid eating nuts during pregnancy in an effort to reduce nut allergy (unless they themselves have an existing nut allergy)34.
Babies can eat nut pastes as first foods
A recent consensus of Australian allergy specialists has developed guidelines for introducing nuts to infants34. Nuts in the form of pastes, butters or flours should be introduced at around 6 months, but not before 4 months, when the infant is ready, just like any other foods. If there is no allergic reaction, the guidance is to gradually increase the amount, and importantly, continue offering the food regularly over time.
To find out more about nut allergy visit Nuts For Life.
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