A food allergy is when the body's immune system reacts to a harmless food as if it were toxic. In most cases, the allergic reaction may cause mild to moderate symptoms such as a rash or an upset tummy. In rare cases, it can cause a severe reaction called anaphylaxis.
Who is affected by food allergy?
Most food allergies start in childhood and are most common in young children aged less than 5 years. Even young babies can develop symptoms of food allergy. Food allergy affects up to 10% of babies, 6% of children and 2% of adults.
Allergies tend to run in families, so a baby with parents who have allergies is at a higher risk of developing food allergy. However, some babies can develop food allergy even though there is no family history of allergy. Read more about reducing food allergies in infants.
Adult onset of food allergy is not common. Food intolerance is much more common in adults and can be due to a variety of causes. Read more about the difference between food allergy and intolerance.
Common allergy-causing foods
The following nine foods are responsible for up to 90% of allergic reactions to food:
- tree nuts such as almonds or cashews
- milk (dairy)
- sesame seeds
In New Zealand, these ingredients must be put on food labels, even if the product only contains very small amounts.
- Most children allergic to cow's milk, soy, wheat or egg will 'outgrow' their food allergy.
- However, peanut, tree nut, seed and seafood allergies tend to be lifelong allergies.
Food allergy can sometimes be dangerous
Although allergic reactions to foods are common in New Zealand, death from anaphylaxis due to food allergy is very uncommon. The most common foods causing life-threatening anaphylaxis are peanuts, tree nuts, shellfish, milk and egg.
Most deaths can be prevented by careful avoidance of foods you are allergic to and immediate use of an adrenaline autoinjector if you do have a severe allergic reaction.
What are the symptoms of food allergy?
Symptoms of an allergic reaction to food normally develop immediately after, or with in hours of, eating.
Mild to moderate symptoms include:
- itching and hives
- swelling around the lips, face and eyes
- tummy pain, diarrhoea (runny poos)
- nausea, vomiting
Signs of a severe allergic reaction (anaphylaxis) include:
- swelling of tongue
- tightness in throat
- difficulty breathing, wheeze
- difficulty talking or hoarse voice
- dizziness and/or collapse
- pale and floppy (in young children)
Anaphylaxis must be treated as a medical emergency, requiring immediate treatment and urgent medical attention – call 111.
How is food allergy diagnosed?
If you are concerned your child may have a food allergy see your GP for diagnosis. Your GP will talk to you about the history of the symptoms being experienced. In some cases when symptoms appear within a few minutes every time of eating the particular food, it makes it easy to identify which food is causing the reaction. However, if the cause is unknown, diagnostic tests may be needed. Your GP may refer your child for a skin prick or blood test, and/or to a paediatric clinic or allergy specialist for further tests.
How is food allergy treated?
Currently, there is no cure for food allergy. Avoidance of the food is the only way to prevent a reaction. This can be difficult, especially if foods are contaminated with traces of another food.
Adrenaline is used to treat severe allergic reactions (anaphylaxis). It can be administered via an auto-injector such as an EpiPen to slow down or stop an allergic reaction.
Researchers continue to explore new ways of more effectively treating food allergies. Treatment of milk and egg allergies now includes recommendations on introducing milk and egg in baked products, following a ‘ladder’, until they can safely eat the raw product. This is felt to help speed up the ‘growing out’ phase rather than desensitise the patient. However, this needs to be done as part of clinical management by a specialist and is not appropriate to all food allergy or patients.
Immunotherapy as a treatment for food allergy involves giving tiny and increasing amounts of the food protein to ‘desensitise’ the immune system to that food. Results from preliminary research into immunotherapy look promising. However this is still very much in the research phase, with a lot of unanswered questions, so not likely to be any recommendations on this for some time to come.
How to prevent allergic reactions?
You can only prevent the symptoms of food allergy by avoiding the food you are allergic to. After you have identified the foods to which you are sensitive, you must remove them from your diet.
Despite your best efforts to avoid particular foods, you may be exposed to it accidentally. Be prepared for this by:
- having an allergy action plan
- wearing a medical alert bracelet or necklace
- carrying an auto-injector device containing adrenaline
Allergy action plans
Many people with food allergies will have an accidental exposure every few years, even when they are very careful to avoid the foods they are allergic to. If you are thought to be at risk for anaphylaxis and have been prescribed an adrenaline autoinjector you need an Action Plan for Anaphylaxis. If you are not thought to be at high risk of anaphylaxis and have not been prescribed an adrenaline autoinjector, you need an Action Plan for Allergic Reactions.
These plans should be completed and provided by your doctor. They are available from the Australian Society of Clinical Immunology & Allergy (ASICA) website.
As there is currently no cure for food allergy, avoidance is essential in the management of food allergy. If you have a severe food allergy:
- carry your adrenaline autoinjector (if prescribed) and ASCIA Action Plan with you at all times
- know the signs and symptoms of mild to moderate and severe allergic reactions (anaphylaxis) and what to do when a reaction occurs
- read and understand food labels for food allergy (see below)
- tell restaurant staff that you have a food allergy when eating out
- be aware of cross-contamination of food allergens when preparing food.
Reading food labels
The Australia New Zealand Food Standards Code requires food labels to declare certain foods and substances in foods. If you are allergic to a certain food, try to learn the different names used to describe that food on food labels, for example:
- egg – eggs, egg albumen, egg yolk, egg lecithin
- lactose – milk, lactose
- milk – non-fat milk solids, cheese, yoghurt, caseinates, whey, lactose
- soy – soybeans, hydrolysed vegetable protein, soy protein isolate, soy lecithin.
For a complete list visit the Australia New Zealand Food Standards website.
Food allergies Ministry for Primary Industries NZ
Food allergy Australian Society of Clinical Immunology and Allergy
Allergy prevention in infants Australian Society of Clinical Immunology & Allergy
The Centre for Food & Allergy Research (CFAR), Melbourne