What body systems are affected by food allergies
Food allergies are divided into 3 types, depending on symptoms and when they occur.
- non-IgE-mediated food allergy – these allergic reactions aren’t caused by immunoglobulin E, but by other cells in the immune system. This type of allergy is often hard to diagnose as symptoms take much longer to develop (up to several hours).
- IgE-mediated food allergy – the most common type, triggered by the immune system producing an antibody called immunoglobulin E (IgE).
Symptoms occur a few seconds or minutes after eating. There’s a greater risk of anaphylaxis with this type of allergy.
- mixed IgE and non-IgE-mediated food allergies – some people may experience symptoms from both types.
Read more information about the symptoms of a food allergy.
Oral allergy syndrome (pollen-food syndrome)
Some people experience itchiness in their mouth and throat, sometimes with mild swelling, immediately after eating unused fruit or vegetables. This is known as oral allergy syndrome.
Oral allergy syndrome is caused by allergy antibodies mistaking certain proteins in unused fruits, nuts or vegetables for pollen.
Oral allergy syndrome generally doesn’t cause severe symptoms, and it’s possible to deactivate the allergens by thoroughly cooking any fruit and vegetables.
The Allergy UK website has more information.
What causes food allergies?
Food allergies happen when the immune system – the body’s defence against infection – mistakenly treats proteins found in food as a threat.
As a result, a number of chemicals are released. It’s these chemicals that cause the symptoms of an allergic reaction.
Almost any food can cause an allergic reaction, but there are certain foods that are responsible for most food allergies.
Foods that most commonly cause an allergic reaction are:
- tree nuts
- some fruit and vegetables
Most children that own a food allergy will own experienced eczema during infancy.
The worse the child’s eczema and the earlier it started, the more likely they are to own a food allergy.
It’s still unknown why people develop allergies to food, although they often own other allergic conditions, such as asthma, hay fever and eczema.
Read more information about the causes and risk factors for food allergies.
When to seek medical advice
If you ponder you or your kid may own a food allergy, it’s extremely significant to enquire for a professional diagnosis from your GP. They can then refer you to an allergy clinic if appropriate.
Many parents mistakenly assume their child has a food allergy when their symptoms are actually caused by a completely different condition.
Commercial allergy testing kits are available, but using them isn’t recommended.
Numerous kits are based on unsound scientific principles. Even if they are dependable, you should own the results looked at by a health professional.
Read more about diagnosing food allergies.
The best way to prevent an allergic reaction is to identify the food that causes the allergy and avoid it.
Research is currently looking at ways to desensitise some food allergens, such as peanuts and milk, but this is not an established treatment in the NHS.
Read more about identifying foods that cause allergies (allergens).
Avoid making any radical changes, such as cutting out dairy products, to your or your child’s diet without first talking to your GP. For some foods, such as milk, you may need to speak to a dietitian before making any changes.
Antihistamines can assist relieve the symptoms of a mild or moderate allergic reaction.
A higher dose of antihistamine is often needed to control acute allergic symptoms.
Adrenaline is an effective treatment for more severe allergic symptoms, such as anaphylaxis.
People with a food allergy are often given a device known as an auto-injector pen, which contains doses of adrenaline that can be used in emergencies.
Read more about the treatment of food allergies.
Most food allergies affect younger children under the age of 3.
Most children who own food allergies to milk, eggs, soya and wheat in early life will grow out of it by the time they start school.
Peanut and tree nut allergies are generally more endless lasting.
Food allergies that develop during adulthood, or persist into adulthood, are likely to be lifelong allergies.
For reasons that are unclear, rates of food allergies own risen sharply in the final 20 years.
However, deaths from anaphylaxis-related food reactions are now rare.
In the most serious cases, a person has a severe allergic reaction (anaphylaxis), which can be life threatening.
Call 999 if you ponder someone has the symptoms of anaphylaxis, such as:
- trouble swallowing or speaking
- breathing difficulties
- feeling dizzy or faint
Ask for an ambulance and tell the operator you ponder the person is having a severe allergic reaction.
What is food intolerance?
A food intolerance isn’t the same as a food allergy.
People with food intolerance may own symptoms such as diarrhoea, bloating and stomach cramps. This may be caused by difficulties digesting certain substances, such as lactose.
However, no allergic reaction takes place.
Important differences between a food allergy and a food intolerance include:
- you need to eat a larger quantity of food to trigger an intolerance than an allergy
- the symptoms of a food intolerance generally happen several hours after eating the food
- a food intolerance is never life threatening, unlike an allergy
Read more about food intolerance.
Sheet final reviewed: 15 April 2019
Next review due: 15 April 2022
|Hives on the back are a common allergy symptom.|
|Symptoms||Itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, low blood pressure|
|Usual onset||Minutes to several hours of exposure|
|Duration||Long term, some may resolve|
|Causes||Immune response to food|
|Risk factors||Family history, vitamin D deficiency, obesity, high levels of cleanliness|
|Diagnostic method||Based on a medical history, elimination diet, skin prick test, oral food challenge|
|Differential diagnosis||Food intolerance, celiac disease, food poisoning|
|Prevention||Early exposure to potential allergens|
|Treatment||Avoiding the food in question, having a plan if exposure occurs, medical alert jewelry|
|Frequency||~6% (developed world)|
A food allergy is an abnormal immune response to food. The symptoms of the allergic reaction may range from mild to severe. They may include itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressure. This typically occurs within minutes to several hours of exposure. When the symptoms are severe, it is known as anaphylaxis. A food intolerance and food poisoning are separate conditions, not due to an immune response.
Common foods involved include cow’s milk, peanuts, eggs, shellfish, fish, tree nuts, soy, wheat, rice, and fruit. The common allergies vary depending on the country. Risk factors include a family history of allergies, vitamin D deficiency, obesity, and high levels of cleanliness. Allergies happen when immunoglobulin E (IgE), part of the body’s immune system, binds to food molecules. A protein in the food is generally the problem. This triggers the release of inflammatory chemicals such as histamine. Diagnosis is generally based on a medical history, elimination diet, skin prick test, blood tests for food-specific IgE antibodies, or oral food challenge.
Early exposure to potential allergens may be protective. Management primarily involves avoiding the food in question and having a plan if exposure occurs. This plan may include giving adrenaline (epinephrine) and wearing medical alert jewelry. The benefits of allergen immunotherapy for food allergies is unclear, thus is not recommended as of 2015[update]. Some types of food allergies among children resolve with age, including that to milk, eggs, and soy; while others such as to nuts and shellfish typically do not.
In the developed world, about 4% to 8% of people own at least one food allergy. They are more common in children than adults and appear to be increasing in frequency. Male children appear to be more commonly affected than females. Some allergies more commonly develop early in life, while others typically develop in later life. In developed countries, a large proportion of people believe they own food allergies when they actually do not own them. The declaration of the presence of trace amounts of allergens in foods is mandatory only in Brazil.