Food Allergies: What are they? A conservative estimate states that around 1% of the world population is suffering from food allergies. It is also estimated that it causes around 100-200 deaths in the US every year. Food allergy is a hypersensitive reaction, i.e., a person’s immune system gives an inappropriate response to a very innocuous antigen. An antigen is any foreign substance (along with a few other properties) that can elicit an immune response. It should be understood, however, that food allergies are different from food intolerance (lactose intolerance), food poisonings and other pharmacological reactions in response to certain foods.
An Inappropriate Immune Response
A food allergy is an immune response against a protein in the food which has somehow escaped the heat of cooking, acidity in the stomach and the effects of digestive enzymes in the stomach. This protein now comes out of the gastrointestinal tract and enters the bloodstream. It is then carried to what are known as secondary lymphoid organs (spleen and lymph nodes) and they activate cells of the immune system which then give an immune response.
A major culprit in these types of hypersensitivity reactions is an immunoglobulin (antibody) produced by the immune system called IgE (Immunoglobulin E). Normally when the body encounters an antigen for the first time, it produces IgM and during secondary reactions, it produces IgG. But an allergen (allergy generating substance) elicits the production of IgE. This IgE binds to the surface of cells called mast cells (present in all major tissues of the body) and basophils (in blood). When the antigen (food protein) binds to these IgEs, they result in the degranulation of mast cells and basophils. These granules contain very active pharmacological compounds which give rise to various symptoms of food allergies.
Symptoms of Food Allergy
All the allergic symptoms can be experienced within minutes to an hour after consuming the food. It may start with itching in the mouth to difficulty in breathing and swallowing. Later on nausea, vomiting, diarrhea and abdominal pain may be experienced. As the allergen enters the blood and subsequently encounters mast cells in skin, it may lead to symptoms like hives or eczema. If it enters the lungs, it can cause asthma. These are what are known as localized reactions. Sometimes a systemic reaction involving the entire body can also be observed. This reaction is referred to as anaphylaxis or anaphylactic shock. This condition can be fatal if not treated immediately.
Common Food Allergens
The most common food allergies are known as “The Big Eight.” These are dairy allergy, egg allergy, peanut allergy, tree nut allergy, seafood allergy, shellfish allergy, soy allergy and wheat allergy. Milk, eggs, peanuts, tree nuts, fish, shellfish, soy, wheat and sesame are amongst the top ten allergens in most countries although these may vary according to region. A food allergy can be diagnosed by taking into account a patient’s history, diet or an elimination diet. Furthermore, it may be confirmed by skin tests, blood tests and food challenge tests.
Treatment of Food Allergy
There is no permanent cure for an allergy and only symptomatic treatment is available. The best way to avoid a food allergy is to avoid the food responsible for it. If the patient accidentally ingests the food, then symptomatic treatment can be given. For an anaphylactic shock, epinephrine (adrenaline) is injected. This could prove a life-saving procedure. For other symptoms, antihistamines and bronchodilators are helpful. Although desensitization procedures reduce the incidence of respiratory or skin allergies, it has not proved useful in reducing food allergies. Some scientists believe that a vaccine can cure food allergies. Food allergies could be eradicated in about ten years. Until such time, the patient has to manage the food allergy.