Members of the public

What is a food allergy?

Food allergy is a globally important public health issue that affects people of all ages, races, and socioeconomic statuses.

When someone has a food allergy, their immune system reacts to a food which can cause an allergic reaction. With many food allergies, reactions are caused by a natural part of the immune system called immunoglobulin E (IgE).

IgE helps to identify things that could be harmful to the body (such as bacteria) and tells other parts of the immune system to release chemicals (such as histamines) to fight the harmful things. With IgE-mediated food allergies, the allergic individual’s immune system has IgE that is specific to the food allergen. For example, with IgE-mediated peanut allergy, a peanut-allergic individual has peanut-specific IgE that can trigger a reaction if that individual is exposed to peanut.

What are the symptoms of food allergies?

IgE-mediated reactions to food allergens typically happen quickly after exposure (within a few minutes to a few hours) and can results in a variety of symptoms that can vary in how severe they are. Symptoms can affect the following areas of the body:

• Skin

  Example: Hives, rash, itching or swelling

• Respiratory system (lungs, throat, nose etc.)

  Example: Wheezing, coughing, runny nose, trouble breathing, trouble speaking

• Gastrointestinal system (mouth, stomach, intestines)

  Example: Stomach pain or cramps, itchy mouth, nausea, vomiting, diarrhoea

• Circulatory system (heart, veins, arteries etc.)

  Example: Weak pulse, loss of consciousness

• Nervous system (brain, spine, nerves etc.)

  Anxiety, agitation, loss of consciousness

Food allergens can also cause a type of reaction known as anaphylaxis. Anaphylaxis affects multiple parts of the body at the same time and can be severe and sometimes life-threatening. The symptoms of anaphylaxis can vary considerably between patients and between episodes of anaphylaxis. Anaphylaxis is a medical emergency that requires immediate treatment.

How common are food allergies?

More than 17 million people in Europe suffer from food allergies, and one in four school-age children in Europe lives with allergic disease.¹

Peanut allergy is one of the most common food allergies and numerous studies indicate that it has increased in prevalence in recent years.²

What are the most common food allergies?

In the UK, the Food Standards Agency requires businesses that sell prepacked food to include precautionary allergen labelling if their product may contain any of the following 14 common food allergens: celery, cereals containing gluten, crustaceans, eggs, fish, lupin, milk, molluscs, mustard, peanuts, sesame seeds, soya, sulphur dioxide and tree nuts.³

How are food allergies diagnosed?

When diagnosing a food allergy, doctors typically review a patient’s medical history and discuss any previous reactions (or suspected reactions) to a food. Additionally, doctors use a few different types of test that can help to diagnose food allergies, including:

• Skin prick testing: Skin is pricked or scratched with a needle that has a tiny amount of suspected food allergen on it. Swelling in area where the skin has been pricked may indicate sensitivity to food allergen.

• Blood testing: Blood is tested to measure food allergen-specific IgE levels. Higher than normal levels, may indicate food sensitivity.

• Food challenge: Tiny amounts of the suspected food allergen, which are slowly increased, are ingested to detect an allergic reaction. Food challenges are performed under medical supervision by doctors who can spot the allergic reaction and treat it if necessary.

Impacts of food allergy

Allergic reactions to a food can vary considerably in severity and can be life-threatening and fatal; however, it is important to note that fatalities are very rare.⁴

It can be challenging to avoid food allergens as many are common ingredients and allergic reactions can be triggered by small amounts of an allergen. For example, the median average amount of peanut protein that leads to objective reactions in real-life accidental exposure is estimated to be 125 mg (about half of one peanut kernel).⁵

Because of this, many food allergic individuals and their families need to be highly vigilant to avoid allergens in their day-to-day lives which can result in stress, limited social activities, and an associated decline in quality of life.