Food allergy
What is a food allergy?
A food allergy occurs when your immune system reacts to specific proteins in food. It should not be confused with food intolerance, such as lactose intolerance.
Food allergies are rapidly increasing and it is not yet clear why. Research is currently focused on trying to identify factors that may be contributing to their increase and to better understand the immune reaction to food allergy.
Causes
Although allergic reactions can be triggered by any type of food, the most common are:
- Eggs;
- Fish;
- Peanuts;
- Milk;
- Shellfish;
- Soy;
- Tree nuts, and;
- Wheat.
The cause of the allergic response is the release of an antibody, called immunoglobulin E (IgE), by a type of immune cell, called a mast cell.
There are some non-IgE mediated allergic reactions, but they are not well understood. They tend to be the type associated with delayed reactions.
Risk factors
Risk factors for food allergy include:
- Family history - if you have a family history of food allergies, you are more likely to suffer from them;
- Age - food allergies are most common in young children, although many children eventually grow out of their allergy;
- Asthma - it is common for asthma and food allergy to occur together. People with asthma and food allergies are more likely to have severe allergic reactions;
- Not breastfeeding - the evidence is not conclusive, but there is some evidence that suggests not being breastfed in infancy increases your risk of developing allergies later in life, and;
- Food-dependent, exercise-induced anaphylaxis (FDEIAn) - this can occur as a result of exercising after consuming food that you are allergic to.
Signs and symptoms
The symptoms of an allergic reaction usually occur within the first two hours after consuming certain foods. Known as immediate reactions, these symptoms include:
- Hives;
- Wheezing;
- A facial or generalized rash;
- Hoarseness of the voice;
- Stomach cramps and abdominal pain;
- Difficulty swallowing;
- Shortness of breath;
- Light-headedness;
- Itching of the mouth, throat, skin, eyes or another area;
- Swelling of the face, lips, tongue and eyelids, and;
- Blocked or runny nose.
Symptoms that usually occur within 1-2 days after ingesting certain foods are called delayed reactions, and include:
A food allergy can cause a rash usually within two hours of eating a certain food.
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Abdominal
Relating to the abdomen, the middle portion of the trunk which contains organs such as the intestines, stomach and liver.
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Wheezing
Breathing with a whistling or rattling sound in the chest.
Methods for diagnosis
Medical history
Your doctor will ask you questions and take a detailed medical history, including family history.
Allergy testing
Skin testing
A small probe coated with a food extract is used to prick or scratch the skin, to test for a reaction. This skin-prick test is usually performed on the skin on the forearm or upper back. It is not painful and can be done on children and adults.
A negative result from a skin-prick test can be used to exclude IgE-mediated allergy.
Skin patch testing for allergies.
Blood tests
A number of blood tests are available to diagnose some specific allergies, but they are expensive and, unlike skin-prick testing, the results are not immediate. Their use tends to be reserved for people with skin conditions such as dermatitis or eczema.
Elimination diets
Elimination diets involve removing certain foods from your diet for a period of time and then reintroducing them in small amounts one at a time to see if symptoms develop. Elimination diets are developed in consultation under the supervision of a dietitian or allergy specialist.
Food diary
You may be asked to record everything you eat or drink in a food diary for a period of time.
Food challenges
You may be offered a supervised food challenge, in which you eat a small amount of food to which you are potentially allergic to, and your reaction is observed. If after 10-15 minutes there is no reaction, you will be given a slightly larger amount. This continues for a couple of hours and if you develop allergic symptoms, it is immediately stopped. Food challenges should only be performed with appropriate medical supervision.
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Blood tests
During a blood test, blood can be drawn using a needle or by a finger prick. Your blood can then be analyzed to help diagnose and monitor a wide range of health conditions.
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Dermatitis
A skin inflammation that may cause redness, itchiness and swelling of the skin. There are different types of dermatitis.
Types of treatment
Adrenaline injector
If you are having an allergic reaction and experience difficulty breathing, tightness in the throat or feel light-headed, immediate treatment with an adrenaline shot or epinephrine auto-injector (commonly known as Epipen®), is usually required to prevent potentially life-threatening complications. It can also be used in children who pass out, cough or vomit repeatedly during an allergic reaction, or who have anaphylaxis (see 'Potential complications'). People with confirmed serious food allergy will often be given an adrenaline injector to carry with them at all times. It is important to seek urgent medical attention after the use of an adrenaline injector for ongoing observation.
Immunotherapy
Immunotherapy involves the regular administration of gradually higher doses of a trigger (allergen) for a food allergy, over a period of years. Immunotherapy can be given as an injection, or as drops or tablets under the tongue. Immunotherapy changes the way the immune system reacts to the trigger, by switching off the allergy. The end result is that you become immune to the triggers, so that you can tolerate them with fewer or no symptoms.
Other therapies
Some people seek out unproven alternative therapies for their food allergy. The Australasian Society of Clinical Immunology and Allergy warns against the following techniques, which are either unproven or ineffective: cytotoxic food testing, pulse testing, reflexology, Vega testing, Alcat testing, Rinkel's intradermal skin testing, kinesiology, hair analysis and immunoglobulin G (IgG) food antibody testing.
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Adrenaline
A substance secreted primarily by the adrenal glands that helps to prepare the body for exertion. It is involved in regulating blood pressure, heart rate and breathing. Adrenaline can also be used as a drug to treat a number of conditions, including cardiac arrest and anaphylaxis.
Potential complications
Anaphylaxis
Anaphylaxis, also called anaphylactic shock, is a severe complication of food allergy that can result in death. If you experience anaphylactic shock, prompt treatment with injectable adrenaline is vital.
Injectable adrenaline is used to treat anaphylaxis.
Other conditions
Food allergies can exacerbate other conditions, such as asthma or eczema.
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Adrenaline
A substance secreted primarily by the adrenal glands that helps to prepare the body for exertion. It is involved in regulating blood pressure, heart rate and breathing. Adrenaline can also be used as a drug to treat a number of conditions, including cardiac arrest and anaphylaxis.
Prognosis
Sometimes children outgrow allergies to milk, soy, egg and wheat if they avoid these foods when they are still young. Allergies that are more likely to be lifelong are those to shellfish, peanuts and tree nuts.
Prevention
There is some evidence to suggest that breastfeeding during infancy reduces the onset of allergies later in life. However, there is no known way to prevent the development of food allergies and if you have a food allergy, the only way to prevent it flaring up is to avoid the food that triggers it.
References
- Allergy and Hypersensitivity - Immunobiology - NCBI Bookshelf. Accessed 17 July 2014 from link here
- Allergy blood test: The Test. Accessed 17 July 2014 from link here
- Combined effects of food and exercise on anap... [Nutr Res Pract. 2013] - PubMed - NCBI. Accessed 17 July 2014 from link here
- Food allergy - National Library of Medicine - PubMed Health. Accessed 17 July 2014 from link here
- Food allergy symptoms and diagnosis. Accessed 17 July 2014 from link here
- Food allergy treatment and avoidance. Accessed 17 July 2014 from link here
- Food allergy: an enigmatic epidemic. [Trends Immunol. 2013] - PubMed - NCBI. Accessed 17 July 2014 from link here
- Food Intolerance - Australasian Society of Clinical Immunology and Allergy (ASCIA). Accessed 17 July 2014 from link here
- Murtagh J. MD. Murtaghs General Practice.
- Oral and sublingual immunotherap... [Asian Pac J Allergy Immunol. 2013] - PubMed - NCBI. Accessed 17 July 2014 from link here
- Use of an epinephrine autoinjector. Accessed 17 July 2014 from link here
11 Most frequently asked questions (FAQs)
Food allergies occur when your immune system overreacts to specific proteins in certain foods. This response can cause anaphylaxis when it is severe, which can result in death if not immediately treated with adrenaline. Food allergies are often confused with food intolerance, such as lactose intolerance. What are the symptoms of food allergy? The symptoms of food allergy include hives, wheezing, swelling in the face, abdominal pain, blocked nose, a diffuse rash on the face or body, difficulty swallowing and in severe cases, breathing difficulties. What causes food allergy? Food allergies are caused by your immune system reacting to specific proteins in food. A type of cell, called mast cells, release an antibody, called IgE. This is known as an IgE-mediated food reaction. Food allergies can also be non-IgE mediated, but these are not well understood. How is food allergy diagnosed? Food allergies can be diagnosed with skin sensitivity testing, blood tests, or by carefully monitoring dietary changes. How is food allergy treated? If you have a food allergy, the main treatment is avoiding the foods that trigger it. If you suffer from a severe allergic reaction or anaphylaxis, you may need to carry an adrenaline injector (commonly known as an EpiPen®) to treat any severe reactions. Can food allergy be prevented? The only way to prevent a food allergy from being triggered is to avoid foods that trigger it. There is some evidence that breastfeeding in infancy can also reduce your child's chances of developing allergies. What is the outlook for food allergy? Often, a food allergy in infancy disappears by the age of five years if you stop eating the food until then. Some allergies remain for life. Managing your diet so you do not eat any food products you are allergic to means you may never suffer an allergic reaction again. How serious a food allergy is depends on how severely you react to food you are allergic to. At its most severe, an allergic reaction can cause anaphylaxis, which can result in death. How common is food allergy? Food allergies are becoming more common and it is not clear why. Research is being done to identify factors that might be causing the rise in cases. What can make food allergy worse? Eating food you are allergic to can trigger an allergic response. The severity of your response may change over time. Although some allergies last for life, some allergies experienced during infancy disappear after the age of five years.
Related topics
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