What are tree nuts?
The term tree nut is commonly used to mean nuts including:
These are different from peanuts (known as groundnuts) because tree nuts come from a different plant family. People who are allergic to peanuts are not necessarily allergic to tree nuts, but people who are allergic to one tree nut have a tendency to be allergic to other tree nuts. (Pine nuts are seeds. Coconuts are not tree nuts and are rarely a cause of allergic reactions.)
What is tree nut allergy?
Tree nut allergy is a reaction that occurs after eating tree nuts. The symptoms usually occur within minutes but sometimes up to 2 hours after eating the nut. These symptoms are due to IgE (allergy) antibodies against nut proteins. In a recent study of Australian nut allergic children, allergy to peanut was the most common (83%), followed by cashew (13%) and other nuts (4%) (almond and pecan, hazelnut and walnut). An allergic reaction to tree nuts often occurs the first time a child is known to eat the nut, often around 2-4 years of age.
How common is tree nut allergy?
In a Western community, about 1 in 500 children (0.2%) react to tree nuts. It seems that allergy to some tree nuts, e.g. cashew nut, is becoming more common. Tree nut allergy is more likely to occur in children with other allergic diseases (asthma, atopic dermatitis, and other food allergies).
What are the symptoms of tree nut allergy?
Reactions can range from mild to severe.
Mild to moderate reactions consist of any one or more of the following:
- hives or welts,
- swelling of the lips/face/eyes,
- tingling of the mouth,
- abdominal pain or vomiting
Severe reactions (anaphylaxis) include one or more of the following:
- Difficulty/noisy breathing,
- swelling of the tongue,
- swelling or tightness in the throat,
- difficulty talking and or hoarse voice,
- wheeze or persistent cough,
- persistent dizziness or collapse, pale and floppy (in young children)
It is rare (but possible) for these severe symptoms to occur alone without hives and/or vomiting.
Reactions to cashew nut are likely to be severe. Very rarely very sensitive people have died from the severe allergic reaction (anaphylaxis).
How is tree nut allergy diagnosed?
In most cases the clue to tree nut allergy is the start of symptoms soon after eating the nut. The presence of allergy IgE antibodies to nut can be confirmed by an allergy skin prick test or a blood test (called a serum specific IgE test). It is important to realise that not every child with a positive allergy test will develop symptoms on eating that nut. The test should be discussed with your doctor. If your child has a positive allergy test, but has never eaten tree nuts, your doctor will discuss the chance of developing a reaction. The allergy tests are not very helpful in telling whether a reaction to nut will be mild or severe.
Can my child also react to peanuts?
There is a low rate of children being allergic to both peanuts and tree nuts. Children with a nut allergy are more likely to be allergic to other tree nuts than to peanuts. E.g., a child with a cashew nut allergy is more likely to react to a pistachio nut (tree nut) than a peanut.
Will my child react to all types of nuts?
Your child is most unlikely to react to all types of nuts; however, allergic reactions to more than one nut are common. Most (>80%) school age children with a nut allergy will have a positive test to at least one other type of nut on allergy testing and 40-50% will be have a reaction to more than one type of nut if exposed. Some children may react to only one type of nut; however, it is simpler to avoid all types of nuts. Foods containing tree nuts often contain more than one type of nut; it is not always possible to be sure which tree nuts are present in a food. Reactions to tree nuts may increase with age. For this reason your doctor may repeat the allergy tests to a range of nuts from time to time. Discuss which nuts your child should avoid with your doctor.
Can my child grow out of tree nut allergy?
Only about 10% of people will outgrow their tree nut allergy. Most preschool children who have tree nut allergy will continue to be allergic during the primary school and teenage years. Those children who have had more severe allergic reactions with breathing problems are less likely to outgrow their allergy than children with milder reactions. Your doctor can sometimes see if the nut allergy is still present by doing allergy tests and by giving your child a supervised challenge in hospital to that nut. Occasionally the nut allergy may come back in people who have outgrown their allergy.
Is my child likely to have a severe reaction from casual contact with tree nuts on benches, other children's hands or by smelling tree nuts?
No. There is no research to confirm that severe reactions from can occur by touching or smelling tree nuts without nut ingestion. Some people can develop localised symptoms e.g. hives where the nut touches the skin and this has the same meaning as a positive skin test. A small number of nut allergic people are sensitive to such small amounts of nuts that they may develop symptoms from eating trace amounts of nuts. Some very sensitive people may develop wheezing if they inhale nut vapours (formed during cooking) but this is extremely rare.
What is an Epipen or Anapen?
Epipens and Anapens are emergency devices called adrenaline autoinjectors that inject a dose of adrenaline into the muscle. They are used to treat severe reactions to nuts (anaphylaxis). The drug adrenaline reverses the severe allergic reaction and can be lifesaving.
Should my child carry an adrenaline autoinjector?
All allergists agree that children who have had a serious reaction with involvement of the breathing passages should have an adrenaline autoinjector. The need for other children to have an adrenalin autoinjector depends on a number of factors which should be discussed with your doctor. If you have an adrenaline autoinjector it is very important that you understand how and when to use it and that you have a written anaphylaxis action plan provided by your doctor.
Can I prevent nut allergy in my future children?
There is no evidence that avoiding nuts in pregnancy or in the diet while breastfeeding prevents nut allergy in babies. Current recommendations include no smoking for either parent, not delaying the introduction of solids unless your child is food allergic (introduce solids between 4-6 months) and breastfeeding for at least 6 months if possible
How do I avoid exposing my child to tree nuts?
Avoiding nuts can be difficult as they are hidden in many foods, especially the following:
- Baked goods – biscuits, cakes, pastries
- Chocolates, ice cream and confectionery/lollies (e.g. Turkish delight)
- Breakfast cereals, muesli, dried fruit mix
- Pesto, pasta sauces, salad dressings
- Asian food, stir fry, vegetarian dishes
It is important to:
- know which nuts to avoid
- learn to how to read food labels carefully - always check the food list on the label even if it says “nut-free” or is a product you have used before.
- understand the different words used to describe tree nuts e.g. almond meal is ground almond nuts
- avoid foods that don’t have a food label or that you haven’t made yourself, as there is no guarantee that the food doesn’t contain nuts
- plan eating out and travelling and talk to staff serving you about your child’s allergy
- avoid food that is served using spoons/tongs that are also used to serve food containing nuts (e.g. some takeaway meals)
- prepare safe meals at home for your child to take out
- change many favourite recipes at home by replacing the nuts with rice bubbles or coconut
- teach your child about their allergy
- beans, legumes (pulses), nutmeg and coconuts are not closely related to nuts and are usually allowed in the diet unless the child has reacted to one of these before.
- Highly refined nut oils are unlikely to cause a reaction in those with a nut allergy. Avoid nut oil which is cold pressed, expressed or expelled
What about foods with a label that says "may contain traces of nuts"?
Many foods carry a warning on the label "may contain traces of nuts." This indicates that the food could have been exposed to tree nuts or peanuts anywhere from the field in which it grew to the factory in which it was produced. However unless there is a mistake the food does not usually contain any nut as an ingredient. Some foods are more likely to be contaminated with nuts than others, especially if they are made on the same machinery as foods containing nuts e.g. chocolate, ice-cream and muesli bars. Discuss what to do about foods labelled "may contain traces of nuts" with your doctor.
This sheet is a guide to avoiding nuts in your child’s diet. Nuts are found in a variety of foods, often in foods we don’t think about such as chocolate, cereal bars/muesli bars, breakfast cereals and bakery items. Your doctor may advise you to avoid a single nut, all types of nuts or a combination of nuts.
Where can I find more information on the Internet?
- Further diet sheets are available on The Sydney Children's Hospitals Network website
- The Australian Society of Clinical Immunology and Allergy (ASCIA) website contains useful information on food allergy written by Australian specialists
- The patient support group Anaphylaxis Australia offers valuable updates and tips for dealing with food allergies
Written by the Department of Allergy and Immunology The Children's Hospital at Westmead.