The Australasian Society of Clinical Immunology and Allergy

Adverse reactions to food can be caused in different ways, by allergy, intolerance, enzyme deficiencies, aversion, toxins or bacterial contamination. Food allergy is common in children and can cause a wide range of symptoms, varying from mild to potentially life-threatening.

It is important to differentiate between causes of adverse reactions

It is important to distinguish between the different causes of adverse reactions to foods, which include:

• Food allergy - occurs when somebody has an immediate (usually within minutes) allergic reaction to food
• Enzyme deficiency - is a lack of certain digestive juices
• Food intolerance - is a reaction to chemicals found in many different foods
• Food aversion - is an emotional dislike of particular foods

Food allergy is common in young children

In infancy and young children, cow's milk and egg allergy are the most common causes of food allergy. However, peanut and soy products are also important. Peanut allergy can be especially dangerous. The following table provides a list of other common food allergens. However, it is important to note that many other foods also cause allergic symptoms.

Food allergy causes a wide range of symptoms

1. The mouth and gut.
Food allergy may cause:

• itching and/or swelling of the lips, tongue, palate and throat, abdominal pain, vomiting and/or diarrhoea.
• Infantile colic - Food allergy may be a cause in about 10% - 15% of colicky infants.
• poor appetite, chronic diarrhoea and a failure to gain weight or 'failure to thrive'. However, it is important to distinguish it from conditions such as inflammatory bowel disease and Coeliac disease.

Coeliac disease is caused by intolerance to gluten in wheat and symptoms include diarrhoea, abdominal distension, failure to thrive, weight loss and occasionally nausea and vomiting.
Coeliac disease is usually diagnosed in early childhood but may be first diagnosed in adults. The treatment of coeliac disease is life long avoidance of gluten containing cereals, especially wheat but also rye, oats and barley.

2. The Skin.
Acute urticaria (hives) and angioedema (swelling of soft tissues) are common symptoms of food allergy occurring within minutes of eating the food. An acute itchy red rash may also occur, lasting from within minutes to two hours after eating food. Skin contact with foods such as raw meat, raw fish, vegetables and fruit can also cause hives. Atopic dermatitis (eczema) in infancy is frequently caused by food allergy, usually milk, egg and soy.

3. Nose, eyes and lungs.
Redness, itching and tearing of eyes as well as blocking, itching and watering of the nose and sneezing can occur. Sometimes chronic ear infections can be caused by food allergy. Food allergy may also be a trigger for asthma in children, but rarely in adults.

4. Anaphylactic shock
This is the most severe allergic reaction, involving many organs of the body, including the:

• Nose - sneezing, blocking, watering and runny nose
• Upper airways - swelling of the throat and vocal cords leading to obstructionof breathing
• Lungs - wheezing and asthma
• Skin - itching hives (urticaria)
• Circulatory system - a fall in blood pressure and collapse

If untreated, anaphylactic shock may cause death. The most common foods causing life-threatening anaphylaxis are peanuts, other nuts and shellfish.
Any patient who has had an anaphylactic shock to any food must wear an identification bracelet and always carry an adrenaline loaded syringe (Epipen) and know how and when to use it. Epipen is available over the counter at pharmacies, but a doctor's advice and instructions must be obtained.
As there is a risk of relapse following anaphylactic shock after the effect of the Epipen has worn off, urgent medical advice should be sought following its use.

Enzyme deficiencies and food intolerances are not allergic reactions

Enzyme deficiencies and food intolerances may sometimes be mistaken for food allergies. However, it is important that they are distinguished from food allergies, to enable appropriate treatment.
Enzyme deficiencies include:

• Lactase deficiency with an inability to digest milk, causing diarrhoea.
• Sucrase-isomaltase deficiency with an inability to digest sugars causing diarrhoea.
• G6PD deficiency causing a serious reaction to Fava beans.

There are many causes of food intolerance, including:

• Irritant substances in foods such as paprika (capsaicin) or stimulant effects of naturally occurring substances in food such as caffeine in coffee and tea.
• Histamine release caused by particular foods such as egg white and strawberries, causing urticaria (hives).
• Vasoactive amines in wine, cheese, bananas, avocados, chocolate and citrus, which act on blood vessels and nerve endings causing facial flushing, urticaria (hives) and headache.
• Food additives such as preservatives and artificial colours - some may cause hives.
• Flavour enhancers - chicken, meat and fish boosters, e.g. monosodium glutamate may cause chest pain associated with palpitations and general weakness, upper abdominal pain, headache, hives and angioedema.
• Food Poisoning is caused by plant toxins such as aflotoxins in mouldy peanuts or soya beans, and bacterial micro-organisms in food, such as salmonella in chicken and bacterial toxins in uncooked meats and certain fish.

Food aversion is a psychological condition

Food aversion is a psychological condition where a person has an unpleasant physical reaction, caused by emotions associated with food rather than the food itself. This reaction does not occur if the food is given in a disguised form.

Diagnosis of food allergy

Diagnosis (or confirmation) of food allergy depends on the use of medically and scientifically proven investigations, including:

• Careful history with particular notice of the time between eating and the start of symptoms
• Daily diet and symptom diary
• Skin prick tests - when good quality food testing extracts, together with negative and positive control skin prick extracts are used, a positive skin prick test indicates the possibility of specific food allergy which will need to be confirmed by challenge tests.
• A negative skin prick test is 95% accurate in confirming the absence of food allergy.
• RAST blood tests for specific foods
• Elimination of suspected food allergen for up to two weeks with improvement of symptoms, followed up by food challenges, except in cases of anaphylactic symptoms. It is important that there is continual follow up by a medical practitioner.
• Challenge with double blind placebo controlled foods, food chemicals and food additives (DBPCFC).

Because there are so many causes of adverse reactions to food, it is important that these investigations are carried out under experienced medical supervision. In particular, diet restrictions and food or food additive challenges should only be undertaken under strict medical supervision.

Unorthodox so-called allergy tests are unproven

There are several methods of unorthodox so-called 'tests' for food allergy which have no scientific basis, are unreliable and hence have no role in the clinical assessment of allergy and asthma. These tests include cytotoxic food testing, vega testing, kinesiology, iridology, pulse testing, Alcat testing and Rinkel's intradermal skin testing.

Understanding food labeling

There are many hidden ingredients in processed food, and labeling may not be helpful or may be actually misleading. National Health and Medical Research Council (NHMRC) approved additive numbers are found in the pamphlet 'Identifying Food Additives' available from the Department of Human Services and Health, G.P.O. Box 9848 in your Capital City.

Food allergy - natural history

Food allergy is most common in early childhood, but many children do not have their food allergy after one year. In the case of milk allergy, nearly 90% lose their allergy by the age of five. In the case of older children and adults, one third lose their symptoms after allergen avoidance within one year, although skin prick tests and RAST may remain positive. However, nearly all peanut, nut, fish and shellfish allergic individuals retain their allergies for life. Food intolerances are usually 'outgrown' except for coeliac disease (gluten enteropathy) which requires a life-long exclusion of Gluten from the diet.

Management of food allergy

The offending food(s) should first be identified, then eliminated from the diet for some time. Reintroduction of foods (except where there has been a life threatening anaphylactic reaction), at regular intervals should be undertaken to see if tolerance has occurred, under the supervision and follow up of a medical practitioner. When several foods need to be eliminated, a dietician's advice should also be sought to ensure that the remaining food intake is nutritionally adequate.

References

1. Hill DJ, Bannister DG, Hoskings CS, Kemp AS. Cow milk allergy within the spectrum of atopic disorders. Clin Exp Allergy 1994; 24(12): 1137-43
2. Kemp AS. Food allergy in children. Aust Fam Physician 1993; 22(11): 1959-63
3. Sampson HA. Food allergy. part 1: Immunopathogenesis and clinical disorders. JACI May 1999, part 1; 103 (5 Pt 1): 717-28
4. Sampson HA. Food allergy. part 2: Diagnosis and management. JACI June 1999; 103 (6): 981-9
5. Sampson HA. Infantile colic and food allergy:fact or fiction? J.Pediatr 1989; 115: 583-584

© ASCIA 2001
The Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional body of Clinical Allergists and Immunologists in Australia and New Zealand.
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ASCIA Education Resources (AER) information bulletins have been peer reviewed by ASCIA members and represent the available published literature at the time of review .
It is important to note that information contained in this bulletin is not intended to replace professional medical advice. Any questions regarding a medical diagnosis or treatment should be directed to a medical practitioner.

Content Last updated December 2001