Topic: Food Allergy
Description
A food allergy is a reaction an individual may experience when they consume a particular food containing a component, called an allergen, to which they are allergic.
What is Food Allergy?
A food allergy is a reaction an individual may experience when they consume a particular food containing a component, called an allergen, to which they are allergic. This reaction, called a hypersensitivity reaction, involves activation of the intestinal immune system and the inappropriate production of antibodies (IgE).
Upon repeated ingestion of the particular food, the IgE antibody and the allergen may interact in a way that leads to the release of a variety of chemical substances, such as histamine. In rare cases, exposure to the food allergen may cause a massive hypersensitivity reaction called anaphylaxis, which may be life-threatening.
Foods commonly responsible for food allergies include nuts (especially peanuts), eggs, fruits, fish, molluscs (oysters, mussels, clam, squid), crustaceans (shrimp, prawns), milk and soy products. Children are affected by food allergies five times more frequently than adults, with about one in 20 children and one in 100 adults affected. Almost two thirds of food allergies begin in the first year of life and the majority are outgrown by the age of ten.
Signs and Symptoms
The chemical substances released may have a variety of effects on the body and can cause symptoms such as:
- abdominal pain
- diarrhoea
- vomiting
- itch of the skin
- rash/hives
- swelling of the lips and mouth
- shortness of breath
- wheeze.
These symptons usually occur within 30 minutes of eating the food of concern. In severe allergies, symptoms of anaphylaxis may develop much earlier. These symptoms include:
- Respiratory symptoms - difficulty breathing, wheeze and shortness of breath due to swelling of the tongue and narrowing of the airways as well as watery eyes and a runny nose.
- Cardiovascular symptoms - racing heart, light headedness, dizziness and chest pain
- Cutaneous symptoms - facial flushing, swelling of the skin and underlying tissue especially around the mouth and eyes, excessive itch and sweaty palms
- Gastrointestinal symptoms - abdominal cramping, nausea, vomiting and diarrhoea
- Other symptoms - feeling of impending doom and headache
Anaphalaxis is a medical emergency and anyone experiencing symptoms of a severe allergic reaction should call 000 immediately.
Symptoms similar to an allergic reaction may be experienced in other medical conditions, it is important to see your doctor to receive a professional diagnosis of food allergy.
Treatment
In mild cases of food allergy (localised skin reaction or mild intestinal symptoms), symptomatic relief may be obtained using antihistamines recommended by the pharmacist, topical application of an anti-itch lotion such as calamine lotion and a cool shower.
More severe reactions, including anaphylaxis, require prompt medical treatment as they may be life-threatening.
Ongoing Management
Following an allergic reaction, an individual may see a specialist, in order to identify other substances to which they are allergic. Several tests may be performed by the doctor, including a skin prick test, blood test and dietary elimination test. The skin prick test involves placing small amounts of various food components onto the skin and looking for any skin changes such as swelling or redness after 10-20 minutes. A blood test can be used to look for any antibodies against particular food components, while the elimination test involves removing certain foods from the diet and then gradually re-introducing them under medical supervision. If symptoms disappear and then redevelop after introducing the food back into the diet, that particular food component may be responsible for the allergic reaction.
Prevention
In order to avoid the effects of a food allergy, an individual should eliminate the particular food from their diet. This may require careful assessment of food labels and specific requests when eating in restaurants. In severe allergies, it may also be necessary to carry a device called an EpiPen in case of accidental exposure to the particular food.
Health Outcome
The majority of food allergies occurring in children are outgrown with time. Even in those people who continue to be allergic to the food throughout life, a good prognosis can be expected if the trigger food is avoided. Deaths from food allergy are rare in Australia.
Further Information
Contrary to popular belief, although symptoms may be similar, food intolerance differs from food allergy. Food intolerance is an adverse reaction in the absence of any immune response and is usually related to the amount of the food consumed rather than simple exposure. Foods commonly responsible for intolerance reactions include dairy products (milk, cheese, yoghurt), chocolate, eggs, food additives and preservatives (MSG), red wine and strawberries. It cannot cause an anaphylactic reaction. Food intolerance may be managed by avoiding the particular food not tolerated.
Other Resources
The Australasian Society of Clinical Immunology and Allergy: Food Allergy
(http://www.allergy.org.au/aer/infobulletins/food_allergy.htm)
The Australasian Society of Clinical Immunology and Allergy: Allergy index
(http://www.allergy.org.au/content/view/290/235/)
Help and Assistance
If you are experiencing a severe allergic reaction please call 000 immediately.
If you have any other symptoms suggesting an allergic reaction or concerns about allergies please contact one of our Registered Nurses at 13 HEALTH by phoning 13 43 25 84.
Last Updated: 1st March, 2011
Date Valid to: 18th October, 2011
