Food allergy

Food allergy
Hives on the back are a common allergy symptom.
Specialty	Emergency medicine, allergy and immunology
Symptoms	Itchiness, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, low blood pressure[1]
Usual onset	Minutes to several hours of exposure[1]
Duration	Long term, some may resolve[2]
Causes	Immune response to food[1]
Risk factors	Family history, vitamin D deficiency, obesity, high levels of cleanliness[1][2]
Diagnostic method	Based on a medical history, elimination diet, skin prick test, oral food challenge[1][2]
Differential diagnosis	Food intolerance, celiac disease, food poisoning[1]
Prevention	Early exposure to potential allergens,[2][3] omalizumab
Treatment	Avoiding the food in question, having a plan if exposure occurs, medical alert jewelry[1][2]
Medication	Adrenaline (epinephrine)[1]
Frequency	~6% (developed world)[1][2]

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.^[1] A food intolerance and food poisoning are separate conditions, not due to an immune response.^[1][4]

Common foods involved include cow's milk, peanuts, eggs, shellfish, fish, tree nuts, soy, wheat, and sesame.^[1][5][2][6] The common allergies vary depending on the country.^[1] Risk factors include a family history of allergies, vitamin D deficiency, obesity, and high levels of cleanliness.^[1][2] Allergies occur when immunoglobulin E (IgE), part of the body's immune system, binds to food molecules.^[1] A protein in the food is usually the problem.^[2] This triggers the release of inflammatory chemicals such as histamine.^[1] Diagnosis is usually based on a medical history, elimination diet, skin prick test, blood tests for food-specific IgE antibodies, or oral food challenge.^[1][2]

Management involves avoiding the food in question and having a plan if exposure occurs.^[2] This plan may include giving adrenaline (epinephrine) and wearing medical alert jewelry.^[1] Early childhood exposure to potential allergens may be protective against later development of a food allergy.^[2][3] The benefits of allergen immunotherapy for treating food allergies are not proven, thus not recommended as of 2015^[update].^[7] Some types of food allergies among children resolve with age, including those to milk, eggs, and soy; while others such as to nuts and shellfish typically do not.^[2]

In the developed world, about 4% to 8% of people have at least one food allergy.^[1][2] They are more common in children than adults and appear to be increasing in frequency.^[2] Male children appear to be more commonly affected than females.^[2] Some allergies more commonly develop early in life, while others typically develop in later life.^[1] In developed countries, more people believe they have food allergies when they actually do not have them.^[8][9][10]