Conditions caused by food allergies are classified into three groups according to the mechanism of the allergic response: # IgE-mediated (classic) – the most common type, manifesting acute changes that occur shortly after eating, and may progress to anaphylaxis # Non-IgE mediated – characterized by an immune response not involving immunoglobulin E; may occur hours to days after eating, complicating diagnosis # IgE and non-IgE-mediated – a hybrid of the above two types Allergic reactions are hyperactive responses of the immune system to generally innocuous substances, such as proteins in the foods we eat. Why some proteins trigger allergic reactions while others do not is not entirely clear, although in part thought to be due to resistance to digestion. Because of this, intact or largely intact proteins reach the small intestine, which has a large presence of white blood cells involved in immune reactions. The heat of cooking structurally degrades protein molecules, potentially making them less allergenic. The pathophysiology of allergic responses can be divided into two phases. The first is an acute response that occurs immediately after exposure to an allergen. This phase can either subside or progress into a "late-phase reaction" which can substantially prolong the symptoms of a response, and result in more tissue damage. In the early stages of acute allergic reaction, lymphocytes previously sensitized to a specific protein or protein fraction react by quickly producing a particular type of antibody known as secreted IgE (sIgE), which circulates in the blood and binds to IgE-specific receptors on the surface of other kinds of immune cells called mast cells and basophils. Both of these are involved in the acute inflammatory response. Activated mast cells and basophils undergo a process called degranulation, during which they release histamine and other inflammatory chemical mediators called (cytokines, interleukins, leukotrienes, and prostaglandins) into the surrounding tissue causing several systemic effects, such as vasodilation, mucous secretion, nerve stimulation, and smooth-muscle contraction. This results in runny nose, itchiness, shortness of breath, and potentially anaphylaxis. Depending on the individual, the allergen, and the mode of introduction, the symptoms can be system-wide (classical anaphylaxis), or localized to particular body systems; asthma is localized to the respiratory system while eczema is localized to the skin. After the chemical mediators of the acute response subside, late-phase responses can often occur due to the migration of other white blood cells such as neutrophils, lymphocytes, eosinophils, and macrophages to the initial reaction sites. This is usually seen 2–24 hours after the original reaction. Cytokines from mast cells may also play a role in the persistence of long-term effects. Late-phase responses seen in asthma are slightly different from those seen in other allergic responses, although they are still caused by release of mediators from eosinophils. Five major allergenic proteins from the<unk>  of the domestic chicken (Gallus domesticus) have been identified; these are designated Gal d 1-5. Four of these are in<unk>  white: ovomucoid (Gal d 1), ovalbumin (Gal d 2), ovotransferrin (Gal d 3) and lysozyme (Gal d 4). Of these, ovomucoid is the dominant allergen, and one that is less likely to be outgrown as children get older. Ingestion of under-cooked<unk>  may trigger more severe clinical reactions than well-cooked<unk> . In<unk>  yolk, alpha-livetin (Gal d 5) is the major allergen, but various vitellins may also trigger a reaction. People allergic to alpha-livetin may experience respiratory symptoms such as rhinitis and/or asthma when exposed to chickens, because the yolk protein is also found in live birds. In addition to IgE-mediated responses,<unk>  can manifest as atopic dermatitis, especially in infants and young children. Some will display both, so that a child could react to an oral food challenge with allergic symptoms, followed a day or two later with a flare up of atopic dermatitis and/or gastrointestinal symptoms, including allergic eosinophilic esophagitis. Non-allergic intolerance<unk>  whites, which are potentially histamine liberators, also provoke a nonallergic response in some people. In this situation, proteins in<unk>  white directly trigger the release of histamine from mast cells. Because this mechanism is classified as a pharmacological reaction, or "pseudoallergy", the condition is considered a food intolerance instead of a true immunoglobulin E (IgE) based allergic reaction. The response is usually localized, typically in the gastrointestinal tract. Symptoms may include abdominal pain, diarrhea, or any other symptoms typical to histamine release. If sufficiently strong, it can result in an anaphylactoid reaction, which is clinically indistinguishable from true anaphylaxis. Some people with this condition tolerate small quantities of<unk>  whites. They are more often able to tolerate well-cooked<unk> s, such as found in cake or dried<unk> -based pasta, than incompletely cooked<unk> s, such as fried<unk> s or meringues, or uncooked<unk> s.
Egg allergy
Corn allergy
Milk allergy
Latex allergy
Poultry allergy
Peanut allergy
Shellfish allergy
Fruit allergy