peanut and tree nut allergy

Severe allergic reactions (anaphylaxis) can be triggered by a wide range of foods. Theoretically almost any food may be implicated, but the most common culprits are peanuts and tree nuts. Tree nuts include cashews, almonds, Brazils, hazelnuts, walnuts, pecans and pistachios. About three-quarters of children allergic to nuts or peanuts will react on their first exposure.

Even very tiny amounts — as little as 1/2000th of a peanut — can cause a life-threatening reaction in some people. Others will experience only mild symptoms, but because severity is difficult to predict all cases should be assessed by an allergy specialist or a GP with a special interest in allergy. Even mild symptoms such as a tingling of the lips should never be ignored because it is possible that future reactions may be more severe.

People at risk of severe reactions may be prescribed an auto-injector of adrenaline, such as an EpiPen.

Peanuts are actually legumes. A small percentage of people with peanut allergy react to other legumes, such as peas, beans and lentils. Care is needed, but most will find they can tolerate these other legumes without problems.

More commonly, people with peanut allergy react to tree nuts. Hence, doctors often advise people with peanut allergy to avoid tree nuts, and vice versa.

Prevalence

There are no prevalence studies in New Zealand, so we base our statistics on overseas. In Australia, about one in 50 children are thought to have a peanut allergy and one in 200 adults.

Is it life-long?

Peanut allergy was once thought to be life-long in all cases. But recently it has been shown that about 20 per cent of young children grow out of their peanut allergy by the age of five. Any five-year-old who has been free of peanut allergy symptoms for more than a year may possibly have outgrown the allergy. The child can be referred to an allergy specialist for “challenge testing”, in which peanuts are introduced to the child in a controlled way. This will be carried out in a hospital setting.

Teenagers

Teenagers and young adults may be more at risk of life-threatening reactions than younger children. But their allergies can be well managed so long as they always carry prescribed medication, learn how to use it, and are extremely vigilant when food is around.

Avoiding peanuts

 
It is important to read food labels thoroughly, even if you are buying a product you have eaten before. Recipes do sometimes change. Check both the inner and outer wrapping of multi-packs.

Roasting and heat treatment do not reduce the allergenicity of peanuts or tree nuts. In fact, laboratory experiments have suggested that roasting and heating peanuts (but not boiling) may increase their allergenicity. There have been no studies involving human subjects so our advice is to avoid all forms of peanuts.

Avoid foods that contain peanuts or any of these ingredients:

• arachis
• arachis oil
• beer nuts
• candle nuts
• chopped nuts
• cold pressed
• earth nuts
• goobers
• ground nuts
• ground nut oil
• mixed nuts
• monkey nuts
• peanut-blanched, butter, chopped, flour, flavour, meal, paste
• peanut oil - cold pressed, expelled, hydrogenated, expressed, extruded
• peanut sprout
• satay sauce or flavour

Note: Always read labels as peanuts may appear in foods not listed here.

Some examples of where peanut protein may be present:

• African, Asian (eg Chinese, Indian, Indonesian, Japanese, Thai, Vietnamese) and Mexican dishes
• baked goods eg biscuits, cakes, pastries, cereals/mueslis, confectionery chocolate, Florentines
• gravy
• hummus
• marzipan
• meat dishes eg chilli
• muesli bars
• nougat
• pesto
• sauces
• tahini
• flavour

Cross-contamination is a common problem with peanuts – serving spoons, cutters etc may be used in more than one dish. Peanut butter is sticky and can remain on knives, benches, chopping boards, kitchen cloths and barbeques. It can end up in the margarine tub or jam jar from someone else’s knife, or transferred to toys, door handles, taps and school desks from sticky fingers. Serving spoons and loose nuts in bulk bins can also end up in other containers.

Avoiding tree nuts

Avoid foods that contain nuts or any of these ingredients:

• almonds
• amaretto
• bitter almonds
• artificial nuts
• Brazil nuts
• caponata
• cashews
• chestnuts
• filbert/hazelnuts
• gevuina nut
• gianduja (nut mixture found in some chocolate)
• gingko
• hickory nuts
• macadamia nuts
• mandelonas
• marzipan/almond paste
• nan-gai nuts
• natural nut extract
• noisette
• nougat
• nut-butter, meal, meat, oil, paste, pieces, spreads
• pecans
• pesto
• pine nuts (also referred to as Indian pinon, pinyon, pignoli, pignolia, and pignon nuts)
• pistachios
• pralines
• walnuts

Note: Always read labels as nuts may appear in foods not listed here.

Some examples of where nut protein may be present:

• African dishes
• Asian dishes eg Chinese, Indian, Indonesian, Thai, Vietnamese
• Mexican dishes
• baked goods eg biscuits, cakes, pastries
• sweets/confectionery
• cereals/mueslis
• chocolate
• ice cream
• muesli bars
• salad dressings
• sauces
• garnishes

Coconuts

Contrary to their name, coconuts are not tree nuts but are monocotyledonous plants of the palm family Arecaceae. Nut bearing trees, on the other hand, are dicots and are only distantly related to the palm species. Coconut rarely causes allergy. Most allergists will not suggest coconut avoidance unless there has been an allergic reaction to coconut.

Travelling

If you are travelling on an international flight, check that they do not serve peanuts as a snack as the airborne particles may cause a reaction. The most likely cause of reactions in flight, however, is through eating peanuts or nuts present in airline food. This is solved by playing it safe and taking your own food on the plane.

Acknowledgements: Dr Jan Sinclair — Paediatric Immunologist, and Jennifer Heyward
 — Paediatric Dietitian, of Starship Children's Health, 
and the Anaphylaxis Campaign.