Food allergy
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]
Food allergy
Minutes to several hours of exposure[1]
Long term, some may resolve[2]
Family history, vitamin D deficiency, obesity, high levels of cleanliness[1][2]
Early exposure to potential allergens,[2][3] omalizumab
Avoiding the food in question, having a plan if exposure occurs, medical alert jewelry[1][2]
Adrenaline (epinephrine)[1]
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.[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]
Food allergy symptoms occur within minutes to hours after exposure and may include:[11]
In some cases, however, onset of symptoms may be delayed for hours.[11]
Symptoms can vary. The amount of food needed to trigger a reaction also varies.[12]
Serious danger regarding allergies can begin when the respiratory tract or blood circulation is affected. The former can be indicated through wheezing and cyanosis. Poor blood circulation leads to a weak pulse, pale skin and fainting.[13]
A severe case of an allergic reaction, caused by symptoms affecting the respiratory tract and blood circulation, is called anaphylaxis. When symptoms are related to a drop in blood pressure, the person is said to be in anaphylactic shock. Anaphylaxis occurs when IgE antibodies are involved, and areas of the body that are not in direct contact with the food become affected and show symptoms.[14] Those with asthma or an allergy to peanuts, tree nuts, or seafood are at greater risk for anaphylaxis.
Causes[edit]
Common food allergies[edit]
Allergic reactions are abnormal immune responses that develop after exposure to a given food allergen.[15] Food allergens account for about 90% of all allergic reactions.[16] The most common food allergens include milk, eggs, peanuts, tree nuts, fish, shellfish, soy, and wheat,[17] which are referred to as "the big eight", and are required by US law to be on labels of foods that contain those foods.[18] In April 2021, President Biden signed the FASTER Act into law. This recognized sesame as the ninth US mandatory food label allergen.[19][20]
Peanuts, a member of the legume family, are one of the most common food allergens that induce reactions in both children and adults.[21] Affecting about 2% of the Western population, peanut allergies tend to cause more severe reactions and anaphylaxis than other food allergies.[22] Tree nuts, including almonds, brazil nuts, cashews, coconuts, hazelnuts, macadamia nuts, pecans, pistachios, pine nuts, and walnuts, are also common allergens. Affected individuals may be sensitive to one particular tree nut or many different ones.[23] Peanuts and seeds, including sesame seeds and poppy seeds, can be processed to extract oils, but trace amounts of protein may also elicit an allergic reaction.[23] Peanut and tree nut allergies are lifelong conditions for the majority of those affected, although evidence shows that ~20% of those with peanut allergies and 9% of those with tree nut allergies may outgrow them.[24]
Egg allergies affect about one in 50 children but are frequently outgrown when children reach age five.[25] Affected individuals can be sensitive to proteins both in the egg white and egg yolk, but most children are allergic to those in the white while most adults are allergic to those in the yolk.[26]
Cow's milk is the most common food allergen in infants and young children, yet many adults are also sensitized to cow's milk.[27] Many affected individuals cannot tolerate dairy products such as cheese and yogurt.[28] A small portion of children with milk allergy, roughly 10%, have a reaction to beef because it contains small amounts of protein that are also present in cow's milk.[29]
Shellfish, which are divided into crustaceans (shrimp, crab, lobster, etc.) and mollusks (mussel, oyster, scallop, squid, octopus, snail, etc.), are the most common food allergy in adults.[30] People may be allergic to other types of seafood, such as fish.[31] Fish allergies were found to be more common in countries that have high fish consumption compared to those with lower consumption.[32]
Other common food allergens include soy and wheat.[33] Those allergic to wheat may be sensitized to any protein in the wheat kernel.[34] To a lesser frequency, people may be mildly allergic to raw fruits and vegetables, a disease known as oral allergy syndrome.[33] Less common allergens include maize, spices, synthetic and natural colors,[35] and chemical additives.[36]
Balsam of Peru, which is in various foods, is in the "top five" allergens most commonly causing patch test reactions in people referred to dermatology clinics.[37]
Social impact[edit]
Food fear has a significant impact on quality of life.[110][111] For children with allergies, their quality of life is also affected by the actions of their peers. An increased occurrence of bullying has been observed, which can include threats or deliberate acts of forcing allergic children to contact foods that they must avoid or intentional contamination of allergen-free food.[153] The social impacts of food allergies can carry over into adulthood.[154]
Portrayal in media[edit]
Media portrayals of food allergy in television and film are not accurate, often used for comedic effect or underplaying the potential severity of an allergic reaction.[155] These tropes misinform the public and also contribute to how entertainment media will continue to wrongly portray food allergies in the future. Types of tropes: 1) characters have food allergies, providing a weakness that can be used to sabotage them. In the movie Parasite a housekeeper is displaced by taking advantage of her peach allergy.[156] In the animated film Peter Rabbit, the farm owner is attacked by being pelted with blackberries, causing an anaphylactic reaction requiring emergency treatment with epinephrine. After many public protests, Sony Pictures and the Peter Rabbit director apologized for making light of food allergies.[157] 2) Food allergy is used for comedic effect, such as in the movies Hitch and in television, Kelso's egg allergy in That '70s Show 3) Food allergies may be incorporated into characters who are also portrayed as annoying, weak and oversensitive, which can be taken as implying that their allergies are either not real or not potentially severe. In season 1, episode 16 of The Big Bang Theory Howard Wolowitz deliberately consumes a peanut-containing food bar (and has a serious reaction) just to delay Leonard from returning to his apartment where a surprise birthday party is being arranged. 4) Any of these portrayals may underplay the potential severity of food allergy, some showing that Benadryl treatment is sufficient.[156] Viewing of humorous portrayals of food allergies has been shown to have a negative effect on related health policy support due to low perceived seriousness.[155]
Research[edit]
Several theories have been suggested to explain why certain individuals develop allergic sensitization instead of oral tolerance to food allergens. One such theory is the dual allergen hypothesis, which states that ingesting food allergens early on promotes oral tolerance while skin exposure leads to sensitization.[95] Instead of oral ingestion, skin barrier disruption in conditions like eczema, for instance, was suggested to cause allergic sensitization in animal and human infants.[48] Inhalation was recently proposed to be an additional sensitization route in the dual allergen hypothesis.[42] Another theory is the barrier regulation hypothesis, describing the role of commensal bacteria in preventing the development of food allergy by maintaining integrity of the intestinal epithelial barrier.[95] Environmental and lifestyle factors, such as early life nutrition and antibiotic treatment, may contribute to food allergy prevalence by affecting gut microbial composition, and thus, intestinal immune homeostasis in infants and young children.[158]
A number of desensitization techniques are being studied.[159] Areas of research include specific oral tolerance induction (also known as oral immunotherapy), and sublingual immunotherapy. The benefits of allergen immunotherapy for food allergies is unclear, thus is not recommended as of 2015.[7]
There is research on the effects of increasing intake of polyunsaturated fatty acids during pregnancy, lactation, via infant formula and in early childhood on the subsequent risk of developing food allergies during infancy and childhood. From two reviews, maternal intake of omega-3, long-chain fatty acids during pregnancy appeared to reduce the risks of medically diagnosed IgE-mediated allergy, eczema and food allergy per parental reporting in the first 12 months of life,[160][161] but the effects were not all sustained past 12 months.[161] The reviews characterized the literature's evidence as inconsistent and limited.[160][161] Results when breastfeeding mothers were consuming a diet high in polyunsaturated fatty acids were inconclusive.[162] For infants, supplementing their diet with oils high in polyunsaturated fatty acids did not affect the risks of food allergies, eczema or asthma either as infants or into childhood.[163]
There is research on probiotics, prebiotics and the combination of the two (synbiotics) as a means of treating or preventing infant and child allergies. From reviews, there appears to be a treatment benefit for eczema,[164][165][166] but not asthma, wheezing or rhinoconjunctivitis.[167] The evidence was not consistent for preventing food allergies and this approach cannot yet be recommended.[165][166][168][169]
The Food Standards Agency, in the United Kingdom, are in charge of funding research into food allergies and intolerance.[152] Since their founding in 1994 they have funded over 45 studies.[152] In 2005 Europe created EuroPrevall, a multi-country project dedicated to research involving allergies.[152]