Food allergies and intolerance
Most of us know someone who has a food allergy or intolerance. It might be a child allergic to peanuts, a workmate who doesn't eat foods with wheat or your mother who has problems drinking milk. So what is the difference between a food allergy and a food intolerance.
A true food allergy is the body’s response to a food protein, such as nuts or fish. The body mistakenly believes the offending protein, known as an allergen, is harmful and creates antibodies to attack it. Reactions can occur within minutes or up to a few hours after eating the food and include:
- difficulty in breathing or swelling in the throat
- swollen or itching lips or tongue
- hives, skin rashes or eczema
- stomach cramps, vomiting or diarrhoea
- faintness or collapse.
About 1% of adults and less than 10% of children are ‘at risk’ of allergic reactions to foods. A small number of foods are responsible for around 90% of food allergies - including shellfish, fish, milk, eggs, peanuts, tree nuts, wheat and soybeans. Peanuts, tree nuts, fish and shellfish are the foods which most commonly cause allergic reactions in adults. Children are commonly allergic to dairy milk and eggs, with the majority growing out of this allergy between the ages of 3 and 5.
Food intolerance can be a result of a sensitivity to naturally occurring chemicals in food. A common food intolerance is to lactose, the sugar found in milk products. This is caused by a shortage of the enzyme lactase needed to help the body break down latse in the stomach. An allergic reaction to milk is also possible when the body reacts to milk protein, although the symptoms will differ.
In food intolerance, the body’s immune system does not create antibodies as in an allergic reaction. However, symptoms can be seen both immediately and up to 20 hours after a food is eaten as in an allergic reaction, so it can be sometimes hard to distinguish between the two.
In contrast to some food allergies, food intolerances aren’t life threatening but they can impact on health and quality of life. Unfortunately, they can be problematic 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.
The smallest traces of a food can trigger an allergic reaction, whereas small amounts of a food can usually be eaten before symptoms appear in most food intolerances. The amount tolerated, however, depends on the individual.
Food allergies and intolerances should be diagnosed by a doctor or specialist before excluding any foods from your diet. Various methods are used to determine allergies and intolerances, including skin prick tests, blood tests, diet histories, food diaries and elimination diets. Self-diagnosing a food allergy or intolerance can increase your nutrition risk as you may be cutting out important foods unnecessarily. If you are diagnosed with a food allergy or intolerance the doctor will advise you if any foods are to be avoided, and may suggest you seek further dietary advice with a registered dietitian or nutritionist.
There is no proven way to prevent food allergies. Breastfeeding babies exclusively until they are six months old, may help reduce the risk. It is recommended women continue to eat common food allergens during pregnancy and breastfeeding. Removing these foods from the diet may put the mother and baby at more risk nutritionally rather than preventing allergies. Delaying the introduction of allergenic foods to infants after six months of age to avoid food allergy is not recommended. If you have concerns please speak to your family doctor, Plunket nurse or consult a registered dietitan.
About one in 300 New Zealanders is affected by coeliac disease, a condition in which the body’s immune system reacts to gluten, found in the grains wheat, rye, barley and oats. This disease causes inflammation of the bowel which affects 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.
Food manufacturers in New Zealand are required to list the most common allergenic foods on their food labels. This includes milk, egg, soy, peanut, tree nut, sesame, fish, shellfish and gluten-containing grains, including wheat. If there is significant risk of cross-contamination, manufacturers also have to include precautionary statements, such as ‘may contain traces of peanuts’. This may occur, for example, if biscuits containing peanuts are produced on the same production line as another biscuit not containing nuts.
Allergy New Zealand offers advice and support to allergy sufferers: www.allergy.org.nz
Coeliac Society of New Zealand: www.coeliac.org.nz
Food & Allergen Labelling, Ministry of Primary Industries website
Food Standards Australia New Zealand: www.foodstandards.govt.nz
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Page Reviewed July 2013