immunology allergic disorders
Food Allergy
Etiology of Food Allergy
Almost any food or food additive can cause an allergic reaction, but the most common triggers include In infants and young children:Milk, soy, eggs, peanuts, and wheat In older children and adults:Nuts and seafood Cross-reactivity between food and nonfood allergens exists, and sensitization may occur nonenterally. For example, patients with oral allergies (typically, pruritus, erythema, and edema of the mouth when fruits and vegetables are eaten) may have been sensitized by exposure to pollens that are antigenically similar to food antigens; children with peanut allergy may have been sensitized by topical creams containing peanut oil used to treat rashes. Many patients who are allergic to latex are also allergic to bananas, kiwis, avocados, or a combination. Food allergies are more common among children whose parents have food allergies, Allergic Rhinitis , or allergic asthma. In general, food allergy is mediated by IgE, T cells, or both: (eg, Urticaria , (eg, dietary protein gastroenteropathies, Celiac Disease ) manifests gradually and is chronic; it is most common among infants and children. (eg, Atopic Dermatitis (Eczema) , eosinophilic gastroenteropathy) tend to be delayed in onset or chronic. Oral allergy syndrome (pollen food allergy syndrome) is caused by proteins in pollens and foods that cross-react (frequently raw fruits and vegetables and nuts). When patients are allergic to a particular pollen protein, the immune system reacts to a similar protein in the food and generates an allergic response. Patients can usually tolerate the food if it is cooked or heated because the food protein is denatured, altering the structure of the proteins that cross-react. The following pollens and foods are commonly associated: Birch pollen: Apples, almonds, carrots, celery, cherries, hazelnuts, kiwi, peaches, pears, and plums Grass pollen: Celery, melons, oranges, peaches, and tomatoes Ragweed pollen: Bananas, cucumbers, melons, sunflower seeds, and zucchini Typical symptoms include itching of the mouth and throat when the causative food is eaten. Although anaphylaxis is not common, it can occur ( Etiology references ). Diagnosis of oral allergy syndrome is usually made clinically but can be confirmed by skin prick testing. Treatment of oral allergy syndrome involves avoiding the food, thoroughly cooking the food to denature the protein, and carrying a prefilled, self-injectingepinephrinesyringe in case of an anaphylactic reaction. This unusual disorder causes pain, cramps, and diarrhea with blood eosinophilia, eosinophilic infiltrates in the gut, and protein-losing enteropathy; patients have a history of atopic disorders. Eosinophilic esophagitismay accompany eosinophilic gastroenteropathy or occur in isolation. Eosinophilic esophagitis is characterized by chronic inflammation of the esophagus and may cause dysphagia, nonacid-related dyspepsia, and dysmotility or, in children, feeding intolerance and abdominal pain. Eosinophilic esophagitis may cause strictures; diagnosis is by endoscopic biopsy. Alpha-gal syndrome refers to a recently discovered form of allergy to red meat ( Etiology references ). Alpha-gal is a sugar molecule (galactose-alpha-1,3-galactose) that occurs in most mammals except for primates (including humans). Also, alpha-gal does not occur in fish, birds, or reptiles. At least one species of tick (lone star tick) has alpha-gal in its saliva. Evidence suggests that the bite (particularly multiple bites) from such ticks may sensitize a person to alpha-gal. Because alpha-gal is present in many red meats (eg, pork, beef, lamb, venison) and in food products derived from mammals (eg, dairy products, gelatin), affected people may develop an IgE-mediated allergic response to these food products. The allergic reactions can include an itchy rash, indigestion, constipation, nausea, and anaphylactic reactions, Unlike other food allergies, symptoms of alpha-gal syndrome frequently do not occur until 3 to 8 hours after eating. 1.Skypala IJ: Can patients with oral allergy syndrome be at risk of anaphylaxis?Curr Opin Allergy Clin Immunol2020 20 (5):459–464, 2020. doi: 10.1097/ACI.0000000000000679 2.Hashizume H, Fujiyama T, Umayahara T, et al: RepeatedAmblyomma testudinariumtick bites are associated with increased galactose-α-1,3-galactose carbohydrate IgE antibody levels: A retrospective cohort study in a single institution.J Am Acad Dermatol78 (6):1135–1141.e3, 2018. doi: 10.1016/j.jaad.2017.12.028 Epub 2017 Dec 19. 