User:Bliu133/Food allergy

Tasks
- Change original "Causes" header in the article to "Common food allergies" (since section only discusses the most common food allergens rather than the underlying root cause for allergic sensitivity) x

- "Prevention" section -> improve organization and structure, move certain sentences to "Treatment" section (ex. sentence about "strict diet" more closely relates to how allergic reactions can be avoided, not how allergies themselves can be prevented), move/delete "Inhalation exposure" as it doesn't relate to allergy prevention, add more information about breastfeeding and early life nutrition as preventative measures

- Add to "Research" section on gut dysbiosis and FA and bacteriotherapy to "Research"

- Add citations for "citation needed"

- Rearranging/rewording sentences of certain sections -> some sentences are awkwardly placed in sections (for ex. "Influenza vaccines are created by injecting a live virus into fertilized chicken eggs. The viruses are harvested, killed and purified, but a residual amount of egg white protein remains. There are options to receive recombinant flu vaccine grown on mammalian cell cultures instead of in eggs. " -> does this deserve its own paragraph? Why separate it from the other forms of allergic exposure?)

- Add "Special Populations" section for infants with food allergies

Common Food Allergies
Allergic reactions are abnormal immune responses that develop after exposure to a given food allergen. Food allergens account for about 90% of all allergic reactions. The most common food allergens include milk, eggs, peanuts, tree nuts, fish, shellfish, soy, and wheat, which are referred to as "the big eight". Sesame may join “the big eight” as a priority allergen in the United States by 2023 as sesame allergies seem to be increasing in many countries.

Peanuts, a member of the legume family, are one of the most common food allergens that induce reactions in both children and adults. Affecting about 2% of the Western population, peanut allergies tend to cause more severe reactions and anaphylaxis than other food allergies. 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. 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. 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.

Egg allergies affect about one in 50 children but are frequently outgrown when children reach age five. 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.

Cow's milk is the most common food allergen in infants and young children, yet many adults are also sensitized to cow's milk. Many affected individuals cannot tolerate dairy products such as cheese and yogurt. 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.

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. People may be allergic to other types of seafood, such as fish. Fish allergies were found to be more common in countries that have high fish consumption compared to those with lower consumption.

Other common food allergens include soy and wheat. Those allergic to wheat may be sensitized to any protein in the wheat kernel. To a lesser frequency, people may be mildly allergic to raw fruits and vegetables, a disease known as oral allergy syndrome. Less common allergens include maize, spices, synthetic and natural colors, and chemical additives.

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.

Routes of exposure
Exposure to certain food proteins triggers the production of antigen-specific immunoglobulin E (IgE) antibodies, which, if unaccompanied by allergic symptoms, is known as allergic sensitization. Oral ingestion is the main sensitization route for most food allergy cases, yet other routes of exposure include inhalation and skin contact.

For example, inhaling airborne particles in a farm-scale or factory-scale peanut shelling/crushing environment, or from cooking, can induce respiratory effects in allergic individuals. Furthermore, peanut allergies are much more common in adults who had oozing and crusted skin rashes as infants, suggesting that impaired skin may be a risk factor for sensitization. An estimated 28.5 million people worldwide are engaged in the seafood industry, which includes fishing, aquaculture, processing and industrial cooking. In these occupational settings, individuals with fish and shellfish allergies are at high risk of exposure to allergenic proteins via aerosolization. Respiratory symptoms may be induced by inhalation of wet aerosols from fresh fish handling, inhalation of dry aerosols from fishmeal processing, and dermal contact through skin breaks and cuts. Another occupational food allergy that involves respiratory symptoms is "baker's asthma," which commonly develops in food service workers who work with baked goods. Previous studies detected 40 allergens from wheat, some cross-reacted with rye proteins and a few cross-reacted with grass pollens.

Allergic sensitization can occur via skin antigen exposure, which usually manifests as hives. The skin has been suggested to be a critical sensitization route for peanut-allergic individuals. Peanut allergies are much more common in adults who had oozing and crusted skin rashes as infants, reinforcing that those with disrupted epithelial barriers, notably the skin barrier, are more prone to skin sensitization. Environmental factors, such as exposure to food, microorganisms, creams, and detergents, may lead to skin barrier dysfunction. Several studies reveal that children exposed to skin creams containing peanut oil are reported to have a higher risk of peanut allergy, suggesting that impaired skin may be a risk factor for sensitization.

Influenza vaccines are created by injecting a live virus into fertilized chicken eggs. The viruses are harvested, killed and purified, but a residual amount of egg white protein remains. There are options to receive recombinant flu vaccine grown on mammalian cell cultures instead of in eggs. --> take out? put somewhere else?

Research
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. Instead of oral ingestion, skin barrier disruption in conditions like eczema, for instance, was suggested to cause allergic sensitization in animal and human infants. Inhalation was recently proposed to be an additional sensitization route in the dual allergen hypothesis. 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. 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.

Prevalence
Food allergies affect up to 10% of the worldwide population, and they are currently more prevalent in children (~8%) than adults (~5) in western nations. In several industrialized countries, food allergies affect up to 10% of children. Children are most commonly allergic to cow's milk, chicken eggs, peanuts, and tree nuts. While studies on adults with food allergy are not as abundant, surveys suggest that the most common food allergens for adults include fish, shellfish, peanuts, and tree nuts.

Food allergies have become increasingly prevalent in industrialized/westernized nations over the last 2-3 decades. An estimated 15 million people currently have food allergies in the United States. In 1997, 0.4% children in the United States were reported to have peanut allergy, yet this number markedly rose to 1.4% in 2008. In Australia, hospital admission rates for food-induced anaphylaxis increased by an average of 13.2% from 1994-2005. One possible explanation for the rise in food allergy is the "old friends" hypothesis, which suggests that non disease causing organisms, such as helminths, could protect against allergy. Therefore, reduced exposure to these organisms, particularly in developed countries, could have contributed towards the increase.

Children of East Asian or African descent who live in westernized countries were reported to be at significantly higher risk of food allergy compared to Caucasian children. Several studies predict that Asia and Africa may experience a growth in food allergy prevalence as the lifestyles there become more westernized.

The prevalence of certain food allergies is suggested to depend partly on the geographical area and country. For instance, allergy to buckwheat flour, used for soba noodles, is more common in Japan than peanuts, tree nuts or foods made from soy beans. Also, shellfish allergy is the most common cause of anaphylaxis in adults and adolescents particularly in East Asian countries like Hong Kong, Taiwan, Singapore, and Thailand. Individuals in East Asia have further developed an allergy to rice, which forms a large part of their diet. Another example is that, out of 9 European countries, egg allergy was found to be most prevalent in the UK and least prevalent in Greece.

Special Populations
About 75% of children who have allergies to milk protein are able to tolerate baked-in milk products, i.e., muffins, cookies, cake, and hydrolyzed formulas. About 50% of children with allergies to milk, egg, soy, peanuts, tree nuts, and wheat will outgrow their allergy by the age of 6. Those who are still allergic by the age of 12 or so have less than an 8% chance of outgrowing the allergy.

References

Pathophysiology
- define allergic sensitization

- make definition of allergic reactions better

Used Sources
Dona DW, Suphioglu C. Egg Allergy: Diagnosis and Immunotherapy. Int J Mol Sci. 2020 Jul 16;21(14):5010. doi: 10.3390/ijms21145010. PMID: 32708567; PMCID: PMC7404024.

Sathe SK, Liu C, Zaffran VD. 2016. Food Allergy. Annual Review of Food Science and Technology 7: 191-220

Flom JD, Sicherer SH. Epidemiology of Cow's Milk Allergy. Nutrients. 2019 May 10;11(5):1051. doi: 10.3390/nu11051051. PMID: 31083388; PMCID: PMC6566637.

Ogata M, Kido J, Nakamura K. Oral Immunotherapy for Children with Cow's Milk Allergy. Pathogens. 2021 Oct 15;10(10):1328. doi: 10.3390/pathogens10101328. PMID: 34684278; PMCID: PMC8539286.

Iweala OI, Choudhary SK, Commins SP. Food Allergy. Curr Gastroenterol Rep. 2018 Apr 5;20(5):17. doi: 10.1007/s11894-018-0624-y. PMID: 29623490; PMCID: PMC5940350.

Skypala IJ. Food-Induced Anaphylaxis: Role of Hidden Allergens and Cofactors. Front Immunol. 2019 Apr 3;10:673. doi: 10.3389/fimmu.2019.00673. PMID: 31001275; PMCID: PMC6457317.

Andreozzi L, Giannetti A, Cipriani F, Caffarelli C, Mastrorilli C, Ricci G. Hypersensitivity reactions to food and drug additives: problem or myth? Acta Biomed. 2019 Jan 29;90(3-S):80-90. doi: 10.23750/abm.v90i3-S.8168. PMID: 30830065; PMCID: PMC6502174.

Sicherer, Scott H.; Sampson, Hugh A. (2018-01-01). "Food allergy: A review and update on epidemiology, pathogenesis, diagnosis, prevention, and management". Journal of Allergy and Clinical Immunology. 141 (1): 41–58.

Lieberman JA, Gupta RS, Knibb RC, Haselkorn T, Tilles S, Mack DP, Pouessel G. 2021. The global burden of illness of peanut allergy: A comprehensive literature review. Allergy 76: 1367-84

Kalic T, Radauer C, Lopata AL, Breiteneder H, Hafner C. 2021. Fish Allergy Around the World-Precise Diagnosis to Facilitate Patient Management. Front Allergy 2: 732178

Lopez CM, Yarrarapu SNS, Mendez MD. 2022. Food Allergies. In StatPearls. Treasure Island (FL): StatPearls Publishing

Copyright © 2022, StatPearls Publishing LLC.

Potential sources
Di Costanzo M, De Paulis N, Biasucci G. 2021. Butyrate: A Link between Early Life Nutrition and Gut Microbiome in the Development of Food Allergy. Life-Basel 11: 384

Gao Y, Nanan R, Macia L, Tan J, Sominsky L, Quinn TP, O'Hely M, Ponsonby AL, Tang MLK, Collier F, Strickland DH, Dhar P, Brix S, Phipps S, Sly PD, Ranganathan S, Stokholm J, Kristiansen K, Gray LEK, Vuillermin P. 2021. The maternal gut microbiome during pregnancy and offspring allergy and asthma. Journal of Allergy and Clinical Immunology 148: 669-78

Iweala OI, Nagler CR. 2019. The Microbiome and Food Allergy. Annual Review of Immunology 37: 377-403

Rachid R, Stephen-Victor E, Chatila TA. 2021. The microbial origins of food allergy. Journal of Allergy and Clinical Immunology 147: 808-13