A food allergy is an inappropriate immune response to a protein in certain foods where the body mistakenly thinks the protein is harmful and creates antibodies to attack it. The most common triggers of food allergies are egg, cow’s milk (dairy), peanut, tree nuts, sesame, soy, wheat, fish and other seafood. While 90% of allergic reactions are attributed to a small number of foods, almost any food can cause an allergic reaction.
The smallest traces of a food can trigger an allergic reaction, and can occur within minutes or up to a few hours after eating the food. Reactions can be mild to moderate, including swelling of the face, lips and/or eyes, hives or welts on the skin, or stomach (abdominal) pain and vomiting. Or they may be severe allergic reactions (anaphylaxis), which affect breathing and the heart, and can be life-threatening. The most common foods causing anaphylaxis are peanuts, tree nuts, shellfish, milk, and egg.
Food allergy occurs in around 5-10% of children and 2-4% of adults in Australia and New Zealand. Children are commonly allergic to cow’s milk and eggs, however, most of them grow out of this allergy by 3-5 years old.
A food intolerance is an unpleasant reaction to a food involving the digestive system – rather than the immune system. Unlike food allergies, small amounts can usually be eaten without causing problems, with wide-ranging individual tolerances. They are not life-threatening but they can impact on health and quality of life.
Symptoms of food intolerance can be seen both immediately and up to 20 hours after a food is eaten. They can be difficult to diagnose as many of the symptoms – such as bloating, wind, diarrhoea and stomach pain – are unspecific and difficult to attribute to a particular food.
For example, lactose intolerance is caused by a deficiency of the enzyme, ‘lactase’ which breaks down lactose (the sugar found in milk). This happens if your body does not make enough lactase, resulting in gut symptoms after eating dairy products, and poor digestion of lactose.
Self-diagnosing a food allergy or intolerance could lead to cutting out core foods or food groups, and worsening nutrition status.
Food allergies and intolerances should be diagnosed by a doctor or allergy specialist before excluding any foods from your diet. A combination of methods are used to determine allergies and intolerances, including skin prick tests, blood tests, diet histories, food diaries and elimination diets. If you are diagnosed with a food allergy or intolerance, your doctor will advise you of any foods to be avoided. They may also suggest you seek further dietary advice with a registered dietitian, especially if you have multiple allergies or intolerances.
Note that there are several misleading tests claiming to diagnose food allergies and intolerances which have been shown to be inaccurate and unreliable in published studies. These include cytotoxic food testing, vega testing, kinesiology, allergy elimination techniques, iridology, pulse testing, alcat testing, Rinkel’s intradermal skin testing, reflexology, hair analysis and IgG food antibody testing.
There is no proven way to prevent food allergies, though the following may help reduce the risk
If you have concerns about what to feed your baby, speak to your family doctor, Plunket nurse or a registered dietitian.
The Food Standards Code requires that common food allergens must be declared on a food label if the allergen is contained in the food in any form (an ingredient, food additive or processing aid).
In February 2021 the Food Standards Code was changed to help people find allergen information on food labels more quickly and easily. The Code now requires food and ingredients to be declared using certain required names and declarations must be made in:
The transition to these new requirements must be complete by February 2026.
A voluntary precautionary allergen statement may be included if there is a risk of cross-contamination for allergens. For example, ‘may contain traces of peanuts’ on the food label of peanut-free biscuits that are produced on the same production line as other biscuits that do contain peanuts.
Coeliac disease is not an allergy but does involve an immune response to gluten (a protein found in the grains wheat, rye, barley, triticale and oats). When gluten-containing cereals are eaten, inflammation of the gut occurs, affecting the body’s ability to absorb nutrients from food, leading to poor nutrition, bloating, weight loss, diarrhoea and fatigue. Coeliac disease is treated by following a strict gluten-free diet. Read more on our gluten page.
Last reviewed 02/05/2023
Last modified: May 23, 2023
