Food allergy is an immunological reaction to food proteins.

Food intolerance is a pharmacological reaction (like the side effects of a drug) to the chemicals in foods.


Family history

Allergy: hay fever, eczema or asthma

Intolerance: migraine, irritable bowel symptoms, behaviour problems

Who is affected?

Allergies are most likely to affect babies and young children because of their underdeveloped immune system.

Intolerances Children are vulnerable because dose for weight they consume a higher dose of food chemicals than adults. Women of child-bearing age are vulnerable because of hormonal influence. Senior citizens are vulnerable because ageing livers and kidneys are slower to excrete chemicals from the body. Exposure to toxic chemicals, pharmaceutical drugs or illness such as gastrointestinal infection can trigger food intolerance.

How common?

Food allergies (not airborne allergies such as pollens) are considered to be relatively rare - affecting up to 8% of babies under 12 months, 3% of children under five, and less than 1% of adults.

Food intolerance is much more common, affecting babies (through breastmilk), children and adults. Some experts suggest 10% are affected, although, in theory, everyone will react if the dose is high enough, so you would expect more people to be affected as levels of additives rise.

Which foods?

People with food allergies typically react to one or two foods. Allergy is produced by a combination of susceptibility and exposure so allergens vary. In Japan, buckwheat, and in the Mediterranean countries, lentils are common allergens. In Australia the most common foods are milk, soy, egg, peanut and fish. Allergies to the last two are more likely to last throughout life.

With food intolerance, food chemicals such as 50 additives and some natural food chemicals are involved, see brochure. These can be in many different foods. For example, asthmatics are most likely to be affected by sulphite preservatives (220-228) in a wide range of foods and drugs including fruit flavoured cordials and drinks, wine, bread, sausages and dried fruit and some medications.


Allergic reactions are quick. They usually occur within 30 minutes and are often easy to identify.

Food intolerance reactions can be delayed up to 48 hours or more. Identification of reactions can be difficult. When problem foods are consumed frequently, symptoms can appear to be a chronic condition rather than a food reaction.


Allergic reactions can be to the tiniest amount of an allergen.

Intolerance reactions to food chemicals are dose-related. Some people are more sensitive than others. In theory, everyone will react to food additives if they consume enough and one study on MSG confirmed this, although a few of the subjects reacted to very high doses which were unlikely to be consumed in one sitting.


Allergic reactions can be itching, swelling, rash, spreading hives, vomiting, diarrhea, breathing difficulties and in the most severe of the allergic disorders, anaphylaxis can lead to collapse and death. By definition, anaphylaxis is an allergic reaction which involves two of the body's systems (eg respiratory and gastrointestinal or skin). Anaphylactic deaths as a result of insect bites or penicillin are usually very quick - within minutes - and due to cardiac arrest, anaphylactic deaths due to food allergies are usually due to suffocation (breathing difficulties).

Food intolerance reactions can be the same as above, as well as:

skin (rashes, swelling)

airways (asthma, stuffy or runny nose, frequent colds and infections)

gastrointestinal tract (irritable bowel symptoms, colic, bloating, diarrhea, vomiting, frequent mouth ulcers, reflux, bedwetting, 'sneaky poos', 'sticky poos')

central nervous system (migraines, headaches, anxiety, depression, lethargy, impairment of memory and concentration, panic attacks, irritability, restlessness, inattention, sleep disturbance, restless legs, moodswings, PMT).

Symptoms of food intolerance can come and go and change throughout life.


Food allergies: involve an IgE response and can be identified by skin prick tests or RAST blood tests and confirmed with avoidance and challenge.

Food intolerance: there are no laboratory tests. The only way to identify provoking foods is through a comprehensive elimination diet and careful challenges.


Food allergies: scrupulous avoidance and retest once a year in the case of babies and children who may grow out of it. Life-threatening peanut allergies in particular are increasing. This is thought to be due to exposure through the use of peanuts in many Western-style processed foods. In allergic families, complete avoidance of peanuts, peanut-containing products (and also cows milk) is recommended for pregnant women for the last six weeks of pregnancy and throughout breastfeeding. Some schools have banned peanut butter.

Food intolerances: an elimination diet with challenges to pinpoint the culprits, gradual reintroduction of certain chemicals to ascertain tolerance, and subsequent avoidance to that limit. The elimination diet we recommend is Failsafe, meaning Free of Additives, Low in Salicylates, Amines and Flavour Enhancers. For an occasional antidote to a reaction, try a pinch of soda bicarb in half a glass of water, or half to one Caltrate plain white 600 mg calcium supplement tablet.

Reference: Clarke L, McQueen J, et al. (1996). "The dietary management of food allergy and food intolerance in children and adults." Australian Journal of Nutrition and Dietetics 53(3): 89-94.