Food allergies are caused by the immune system’s reaction to a food ingredient (typically a protein) that it believes to be harmful. As a result, antibodies and other chemicals, including histamine, are released by the body to expel the protein “invader” from the body. Allergies affect those who are sensitive to a specific food allergen.
Depending on the food allergen involved and the sensitivity of individuals, symptoms associated with food allergies can appear immediately or take several hours or days to manifest. Symptoms can range from mild irritation to life-threatening anaphylaxis
– a whole body allergic reaction that can impair breathing, cause a dramatic drop in blood pressure, affect the heart rate, and result in a loss of consciousness. Without immediate treatment, such as an emergency epinephrine shot and expert care, anaphylaxis can be fatal.
The symptoms of food allergy can include:
- Skin rash, itching, hives
- Swelling of eyes, red eyes or itchy and/or watery eyes
- Tingling or itching in the mouth
- Swelling of the lips, tongue or throat, difficulty swallowing
- Shortness of breath, trouble breathing, wheezing
- Dizzy and lightheaded
- Stomach pain, vomiting, diarrhoea
- Chest pain
- Anaphylactic shock
Food allergy can be divided into 3 classes depending on symptoms and when they occur.
- IgE-mediated food allergy
IgE -mediated food allergy is the most common type of allergy. It is triggered by our immune system producing an antibody called immunoglobulin E (IgE), which in turn causes the release of inflammatory chemicals, such as histamine. Symptoms usually develop within minutes to 1-2 hours after eating the allergen. This class of food allergy is most commonly associated with severe reactions, such as anaphylaxis.
- Non-IgE-mediated food allergy
Non-IgE-mediated food allergy is triggered by other components of the immune system rather than IgE-mediated. It primarily affects the mucous membrane layer of the stomach. Symptoms typically do not appear immediately after eating the allergen and usually are associated with vomiting, bloating and diarrhoea. The most common reaction that people experience is coeliac disease, which is a sensitivity to gluten (found in wheat, rye, barley, and oats) that causes chronic diarrhoea, expansion of the abdomen due to accumulation of gas or liquid, weight loss and inadequate absorption of nutrients.
- Mixed IgE and non-lgE-mediated food allergy
Some people may experience symptoms from both types of allergies. This is known as a mixed IgE and non-IgE-mediated food allergy.
It can be difficult sometimes to determine whether someone has a food intolerance or an allergy as some symptoms overlap. As such, it is important that you consult a medical professional to ensure proper treatment.
The 8 Major Classes of Food Allergens
Foods that cause hypersensitivity reaction in people are known as food allergens. Currently, there are more than 170 foods which are known to cause allergic reactions. Of these, the eight most common allergens are milk, egg, fish, crustacean, soya beans, peanuts, tree nuts and wheat (Food and Agriculture Organization).
The global community has recognised the importance of allergenic consumers being provided with such information. As such, the international food standards setting body, the Codex Alimentarius Commission Committee on Food Labelling, has recommended that these eight foods must be declared on the labels of pre-packaged foods.