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HealthInfo Waitaha Canterbury

Food allergies

Food allergies occur when your immune system overreacts to a food that is harmless to most people. Your body’s immune system treats the food as an invader and produces an allergic reaction to get rid of it.

Most food allergies start in childhood. They're most common in young tamariki (children) under 5 years and affect up to 10% of them. Even young pēpi (babies) can develop symptoms of food allergy.

Most tamariki allergic to cow's milk, soy, wheat or egg will outgrow their food allergy. About 80% of tamariki eventually tolerate these foods by 5 years of age. But peanut, tree nut, seed and seafood allergies tend to be lifelong allergies.

Food allergy is not hereditary (passed down in families), but a pēpi with parents who have food allergies is more likely to develop food allergy. Some pēpi develop a food allergy even though there is no family history of it. Read more about preventing food allergies in babies.

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 about the difference between food allergy and intolerance.

Common allergy-causing foods include peanuts, tree nuts such as almonds or cashews, milk or milk products, eggs, sesame seeds, fish, shellfish, kiwifruit, soy or soybean products, wheat and lupin.

In New Zealand, these ingredients must be put on food labels, even if the product only contains very small amounts.

Symptoms of food allergies

Not all bad reactions to foods are due to allergy. They can be due to food intolerance, toxic reactions, food poisoning, enzyme deficiencies or food aversion. Symptoms of adverse reactions to foods can include headaches after having chocolate or red wine or bloating after drinking a milkshake or eating pasta.

Symptoms of an allergic reaction to food normally develop immediately after, or within hours of eating. 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.

Mild to moderate symptoms include:

Severe allergic reaction (anaphylaxis) signs include:

Important

Anaphylaxis can cause death and is a medical emergency. If you think you or someone near you is suffering from anaphylaxis and they have an adrenaline pen or injection, give them adrenaline then immediately phone 111. Watch this short video on how to use an adrenaline autoinjector (all brands are similar and work the same way).

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 eggs.

Most deaths can be prevented by carefully avoiding foods you're allergic to and immediately using an adrenaline autoinjector if you do have a severe allergic reaction.

Diagnosing food allergies

If you're concerned you or your tamaiti (child) may have a food allergy, see your general practice team for a diagnosis. It's important to get a reliable diagnosis of food allergy before restricting a particular food in your or your child’s diet as this can cause malnutrition.

Your general practice team will ask you or your tamaiti about allergic symptoms, such as a rash or an upset stomach and their relationship to food. It's easy to identify which food is causing the reaction when symptoms appear rapidly after eating it. But if the cause is unknown, other diagnostic tests may be needed.

Your general practice team may refer you or your tamaiti for a skin prick test or a blood test to test for the presence of an antibody that causes an allergic reaction. They may also refer you or your tamaiti to a paediatric clinic or allergy specialist for further tests if the cause is still unclear.

Treating food allergies

If you have a mild or moderate allergic reaction, the treatment aims to relieve your symptoms. Antihistamines are the most used medicines. These relieve itching or hives on your skin. Examples include cetirizine and loratadine.

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 a severe allergic reaction. If you have a food allergy and are thought to be at higher risk of developing anaphylaxis, your general practice team or pharmacist can teach you how to inject adrenaline using an EpiPen.

You'll also need to have an anaphylaxis action plan that documents what to do if you have anaphylaxis and when to call for help. Read more about anaphylaxis.

There is currently no known cure for food allergy. The use of desensitisation known as oral immunotherapy is being researched.

Preventing food allergies

You can only prevent the symptoms of food allergy by avoiding the food you're allergic to. After you've identified the foods you're sensitive to, you must remove them from your or your child’s diet.

Some of the ways to minimise your risk or your child’s risk of being exposed to a particular food allergen include:

Reading and checking food labels

The Australia New Zealand Food Standards Code requires food labels to declare certain foods and substances in foods. If you're allergic to a certain food, try to learn the different names used to describe that food on food labels. For information about this, see the Ministry for Primary Industries' booklet Eating safely when you have food allergies.

Self-care with food allergies

Despite your best efforts to avoid particular foods, you may be exposed to it accidentally. Be prepared for this by:

  HealthInfo recommends the following pages

On the next page: Preventing food allergies in babies

Content shared between HealthInfo Canterbury, KidsHealth and Health Navigator NZ as part of a National Health Content Hub collaborative. Page created July 2022.

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