Food allergies are an immune system overreaction
Food allergy happens when a person's immune system overreacts to a protein in food. In a person who is allergic, the immune system reacts to the protein by over-producing a special group of antibodies – immunoglobulin E. These antibodies are responsible for the symptoms of the allergic reaction.
A food that causes an allergy is called an allergen. For some people, only a tiny trace can trigger a reaction.
The 8 foods that trigger most allergies
Eight foods are responsible for 90% of allergic reactions to foods. These 8 foods are egg, cow's milk, peanuts, soy, fish, seafood, wheat, and tree nuts.
Egg, cow's milk and peanut allergies are the most common food allergies among children. Most children outgrow their allergy to cow's milk by age 5, and egg allergies by age 7.
Shellfish allergy is more common among adults than children.
Peanut allergy is equally common among children and adults and individuals often experience more severe symptoms and are less likely to outgrow their allergy. When eliminating food groups from your diet, supervision by a dietitian is highly recommended.
Managing a food allergy
Most allergic individuals manage their food allergy by avoiding the food that triggers the reaction. Even small amounts of the offending food can cause serious reactions in susceptible individuals.
If you, or your child, are diagnosed with a food allergy you should talk to your doctor about what you can eat. Some people with a food allergy should avoid all sources of that food, while other people can tolerate a small amount of the food allergen, especially if it is cooked.
Research suggests children have a better chance of growing out of a food allergy if they completely avoid the food. To find out whether you are still allergic or have grown out of an allergy, you can be re-tested.
Eating Safely When you have Food Allergies [PDF, 3 MB]
Symptoms of a food allergy
Symptoms of a food allergy range from mild discomfort to severe or life-threatening reactions requiring immediate medical attention. Symptoms include:
- skin problems – hives, eczema, swelling, itching
- respiratory problems – sneezing, asthma, difficulty breathing, cough
- gastrointestinal – swelling and itching of the lips and mouth, vomiting, reflux, colic, diarrhoea, cramps
- circulation problems – low blood pressure, dizziness
- anaphylactic shock – a severe reaction affecting one or more organ systems, for example respiratory, cardiovascular and gastrointestinal systems. Swelling of the airways, drop in blood pressure and difficulty breathing are some of the more serious symptoms.
How allergies are identified
Your doctor or specialist will want your reaction history and will probably do a physical examination. There are also tests to help identify a food allergy.
Getting professional help
Health professionals that can help are
- your general practitioner (GP) or family doctor
- an allergy specialist or paediatrician. You'll need a referral from your GP unless you are in Auckland or Christchurch where there are private allergy specialists
- a dietitian. To see a public hospital dietitian requires a referral from your GP. Otherwise see a private dietitian.