Editing Dermatitis (section)

==Cause==
The cause of dermatitis is unknown but is presumed to be a combination of genetic and environmental factors.<ref name=NIH2013/> Eczema is not contagious.

===Environmental===
The [[hygiene hypothesis]] postulates that the cause of [[asthma]], eczema, and other allergic diseases is an unusually clean environment in childhood which leads to an insufficient [[human microbiota]]. It is supported by epidemiologic studies for asthma.<ref>{{cite journal | vauthors = Bufford JD, Gern JE | title = The hygiene hypothesis revisited | journal = Immunology and Allergy Clinics of North America | volume = 25 | issue = 2 | pages = 247–262, v–vi | date = May 2005 | pmid = 15878454 | doi = 10.1016/j.iac.2005.03.005 }}</ref> The hypothesis states that exposure to bacteria and other immune system modulators is important during development, and missing out on this exposure increases the risk for asthma and allergy.<ref name="auto">{{cite web |url=https://www.lecturio.com/concepts/atopic-dermatitis-eczema/ | title= Atopic Dermatitis (Eczema)
|website=The Lecturio Medical Concept Library |access-date= 2 July 2021}}</ref> One systematic review of literature on eczema found that [[Urban area|urban]] areas have an increased prevalence of eczema compared to rural areas.<ref>{{cite journal |last1=Schram |first1=M.E. |last2=Tedja |first2=A.M. |last3=Spijker |first3=R. |last4=Bos |first4=J.D. |last5=Williams |first5=H.C. |last6=Spuls |first6=Ph.I. |title=Is there a rural/urban gradient in the prevalence of eczema? A systematic review |journal=British Journal of Dermatology |date=16 March 2010 |volume=162 |issue=5 |pages=964–973 |doi=10.1111/j.1365-2133.2010.09689.x |pmid=20331459 |s2cid=205259960 |url=https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2133.2010.09689.x |access-date=8 March 2022 |issn=0007-0963}}</ref> While it has been suggested that eczema may sometimes be an allergic reaction to the [[excrement]] from [[house dust mite]]s,<ref name="pmid2873316">{{cite journal | vauthors = Carswell F, Thompson S | title = Does natural sensitisation in eczema occur through the skin? | journal = Lancet | volume = 2 | issue = 8497 | pages = 13–15 | date = July 1986 | pmid = 2873316 | doi = 10.1016/S0140-6736(86)92560-2 | s2cid = 23111491 }}</ref> with up to 5% of people showing antibodies to the mites,<ref name="pmid17633128">{{cite journal | vauthors = Henszel Ł, Kuźna-Grygiel W | title = [House dust mites in the etiology of allergic diseases] | language = pl | journal = Annales Academiae Medicae Stetinensis | volume = 52 | issue = 2 | pages = 123–127 | year = 2006 | pmid = 17633128 }}</ref> the overall role this plays awaits further corroboration.<ref>{{eMedicine|Derm|38|Atopic Dermatitis}}</ref>

====Malnutrition====
[[Essential fatty acid deficiency]] results in a dermatitis similar to that seen in [[zinc deficiency|zinc]] or [[biotin deficiency]].<ref name="Andrews">{{cite book |url=https://books.google.com/books?id=UEaEDwAAQBAJ&pg=PA482 |page=482 |title=Andrews' Diseases of the Skin: Clinical Dermatology |isbn=978-0-323-55188-5 |last1=James |first1=William D. |last2=Elston |first2=Dirk |last3=Treat |first3=James R. |last4=Rosenbach |first4=Misha A. |last5=Neuhaus |first5=Isaac |year=2019 |publisher=Elsevier Health Sciences }}</ref>

===Genetic===
A number of genes have been associated with eczema, one of which affects production of [[filaggrin]].<ref name=Mc2012/> Genome-wide studies found three new [[copy-number variation|genetic variants]] associated with eczema: OVOL1, ACTL9 and IL4-KIF3A.<ref>{{cite journal | vauthors = Paternoster L, Standl M, Chen CM, Ramasamy A, Bønnelykke K, Duijts L, etal | title = Meta-analysis of genome-wide association studies identifies three new risk loci for atopic dermatitis | journal = Nature Genetics | volume = 44 | issue = 2 | pages = 187–192 | date = December 2011 | pmid = 22197932 | pmc = 3272375 | doi = 10.1038/ng.1017 }}</ref>

Eczema occurs about three times more frequently in individuals with [[celiac disease]] and about two times more frequently in relatives of those with celiac disease, potentially indicating a [[Heredity|genetic]] link between the conditions.<ref>{{cite journal | vauthors = Caproni M, Bonciolini V, D'Errico A, Antiga E, Fabbri P | title = Celiac disease and dermatologic manifestations: many skin clue to unfold gluten-sensitive enteropathy | journal = Gastroenterology Research and Practice | volume = 2012 | pages = 952753 | year = 2012 | pmid = 22693492 | pmc = 3369470 | doi = 10.1155/2012/952753 | publisher = Hindawi Publishing Corporation | doi-access = free }}</ref><ref>{{cite journal | vauthors = Ciacci C, Cavallaro R, Iovino P, Sabbatini F, Palumbo A, Amoruso D, Tortora R, Mazzacca G | title = Allergy prevalence in adult celiac disease | journal = The Journal of Allergy and Clinical Immunology | volume = 113 | issue = 6 | pages = 1199–1203 | date = June 2004 | pmid = 15208605 | doi = 10.1016/j.jaci.2004.03.012 }}</ref>