Editing Asthma (section)

===Environmental===
{{See also|Asthma-related microbes}}

Many environmental factors have been associated with asthma's development and exacerbation, including allergens, air pollution, and other environmental chemicals.<ref name="pmid21623970">{{cite journal |vauthors=Kelly FJ, Fussell JC |date=August 2011 |title=Air pollution and airway disease |journal=Clinical and Experimental Allergy |volume=41 |issue=8 |pages=1059–71 |doi=10.1111/j.1365-2222.2011.03776.x|pmid=21623970 |s2cid=37717160 }}</ref> There are some substances that are known to cause asthma in exposed people and they are called [[asthmagen]]s. Some common asthmagens include ammonia, latex, pesticides, solder and welding fumes, metal or wood dusts, spraying of isocyanate paint in vehicle repair, formaldehyde, glutaraldehyde, anhydrides, glues, dyes, metal working fluids, oil mists, moulds.<ref>{{cite web | url=https://www.health.ny.gov/environmental/workplace/lung_disease_registry/toolkit/asthmagens.htm | title=Occupational Asthmagens – New York State Department of Health}}</ref><ref>{{cite web | url=https://www.hse.gov.uk/foi/internalops/og/og-00016.htm | title=Occupational Asthmagens – HSE}}</ref> [[Smoking and pregnancy|Smoking during pregnancy]] and after delivery is associated with a greater risk of asthma-like symptoms.<ref name="GINA2011_p6">{{harvnb|GINA|2011|p=6}}</ref> Low [[Air quality index|air quality]] from environmental factors such as [[Exhaust gas|traffic pollution]] or high [[ozone]] levels<ref name="GINA2011_p61">{{harvnb|GINA|2011|p=61}}</ref> has been associated with both asthma development and increased asthma severity.<ref name="Gold">{{cite journal|vauthors=Gold DR, Wright R|year=2005|title=Population disparities in asthma|journal=Annual Review of Public Health|volume=26|pages=89–113|doi=10.1146/annurev.publhealth.26.021304.144528|pmid=15760282|s2cid=42988748 |doi-access=}}</ref> Over half of cases in children in the United States occur in areas when air quality is below the [[EPA]] standards.<ref>{{cite journal|title=Urban Air Pollution and Health Inequities: A Workshop Report|journal=Environmental Health Perspectives |volume=109 |issue=s3 |year=2001 |pages=357–374 |issn=0091-6765 |doi=10.2307/3434783|doi-access=free |jstor=3434783 |pmc=1240553 |pmid=11427385 |author1=American Lung Association }}</ref> Low air quality is more common in [[Socioeconomic status|low-income]] and minority communities.<ref>{{cite journal| vauthors = Brooks N, Sethi R |date=February 1997|title=The Distribution of Pollution: Community Characteristics and Exposure to Air Toxics|journal=Journal of Environmental Economics and Management|volume=32|issue=2|pages=233–50|doi=10.1006/jeem.1996.0967|doi-access=free|bibcode=1997JEEM...32..233B }}</ref>

Exposure to indoor [[volatile organic compounds]] may be a trigger for asthma; [[formaldehyde]] exposure, for example, has a positive association.<ref name="pmid20064771">{{cite journal|vauthors=McGwin G, Lienert J, Kennedy JI|date=March 2010|title=Formaldehyde exposure and asthma in children: a systematic review|journal=Environmental Health Perspectives|volume=118|issue=3|pages=313–7|doi=10.1289/ehp.0901143|pmc=2854756|pmid=20064771|bibcode=2010EnvHP.118..313M }}</ref> [[Phthalate]]s in certain types of [[PVC]] are associated with asthma in both children and adults.<ref>{{cite journal|vauthors=Jaakkola JJ, Knight TL|date=July 2008|title=The role of exposure to phthalates from polyvinyl chloride products in the development of asthma and allergies: a systematic review and meta-analysis|journal=Environmental Health Perspectives|volume=116|issue=7|pages=845–53|doi=10.1289/ehp.10846|pmc=2453150|pmid=18629304|bibcode=2008EnvHP.116..845J }}</ref><ref name="pmid20059582">{{cite journal|vauthors=Bornehag CG, Nanberg E|date=April 2010|title=Phthalate exposure and asthma in children|journal=International Journal of Andrology|volume=33|issue=2|pages=333–45|doi=10.1111/j.1365-2605.2009.01023.x|pmid=20059582|doi-access=free}}</ref> While exposure to [[pesticide]]s is linked to the development of asthma, a cause and effect relationship has yet to be established.<ref name="MamJune2015">{{cite journal|vauthors=Mamane A, Baldi I, Tessier JF, Raherison C, Bouvier G|date=June 2015|title=Occupational exposure to pesticides and respiratory health|journal=European Respiratory Review|volume=24|issue=136|pages=306–19|doi=10.1183/16000617.00006014|pmid=26028642|pmc=9487813 |doi-access=free}}</ref><ref name="MamSept2015">{{cite journal|vauthors=Mamane A, Raherison C, Tessier JF, Baldi I, Bouvier G|date=September 2015|title=Environmental exposure to pesticides and respiratory health|journal=European Respiratory Review|volume=24|issue=137|pages=462–73|doi=10.1183/16000617.00006114|pmid=26324808|pmc=9487696 |doi-access=free}}</ref> A [[meta-analysis]] concluded gas stoves are a major risk factor for asthma, finding around one in eight cases in the U.S. could be attributed to these.<ref>{{cite journal | vauthors = Gruenwald T, Seals BA, Knibbs LD, Hosgood HD | title = Population Attributable Fraction of Gas Stoves and Childhood Asthma in the United States | journal = International Journal of Environmental Research and Public Health | volume = 20 | issue = 1 | pages = 75 | date = December 2022 | pmid = 36612391 | pmc = 9819315 | doi = 10.3390/ijerph20010075 | doi-access = free }}</ref>

====Pregnancy====
The evidence does not support a causal role between [[paracetamol]] (acetaminophen) or antibiotic use and asthma.<ref>{{cite journal | vauthors = Heintze K, Petersen KU | title = The case of drug causation of childhood asthma: antibiotics and paracetamol | journal = European Journal of Clinical Pharmacology | volume = 69 | issue = 6 | pages = 1197–209 | date = June 2013 | pmid = 23292157 | pmc = 3651816 | doi = 10.1007/s00228-012-1463-7 }}</ref><ref>{{cite journal | vauthors = Henderson AJ, Shaheen SO | title = Acetaminophen and asthma | journal = Paediatric Respiratory Reviews | volume = 14 | issue = 1 | pages = 9–15; quiz 16 | date = March 2013 | pmid = 23347656 | doi = 10.1016/j.prrv.2012.04.004 }}</ref> A 2014 systematic review found that the association between paracetamol use and asthma disappeared when respiratory infections were taken into account.<ref>{{cite journal | vauthors = Cheelo M, Lodge CJ, Dharmage SC, Simpson JA, Matheson M, Heinrich J, Lowe AJ | title = Paracetamol exposure in pregnancy and early childhood and development of childhood asthma: a systematic review and meta-analysis | journal = Archives of Disease in Childhood | volume = 100 | issue = 1 | pages = 81–9 | date = January 2015 | pmid = 25429049 | doi = 10.1136/archdischild-2012-303043 | s2cid = 13520462 | url = https://epub.ub.uni-muenchen.de/37262/ }}</ref> Maternal [[psychological stress]] during pregnancy is a risk factor for the child to develop asthma.<ref>{{cite journal | vauthors = van de Loo KF, van Gelder MM, Roukema J, Roeleveld N, Merkus PJ, Verhaak CM | title = Prenatal maternal psychological stress and childhood asthma and wheezing: a meta-analysis | journal = The European Respiratory Journal | volume = 47 | issue = 1 | pages = 133–46 | date = January 2016 | pmid = 26541526 | doi = 10.1183/13993003.00299-2015 | doi-access = free }}</ref>

====Allergens====
Asthma is associated with exposure to indoor allergens.<ref name="pmid21301330">{{cite journal | vauthors = Ahluwalia SK, Matsui EC | title = The indoor environment and its effects on childhood asthma | journal = Current Opinion in Allergy and Clinical Immunology | volume = 11 | issue = 2 | pages = 137–43 | date = April 2011 | pmid = 21301330 | doi = 10.1097/ACI.0b013e3283445921 | s2cid = 35075329 }}</ref> Common indoor allergens include [[dust mite]]s, [[cockroach]]es, [[animal dander]] (fragments of fur or feathers), and mould.<ref name=Arshad>{{cite journal | vauthors = Arshad SH | s2cid = 30418306 | title = Does exposure to indoor allergens contribute to the development of asthma and allergy? | journal = Current Allergy and Asthma Reports | volume = 10 | issue = 1 | pages = 49–55 | date = January 2010 | pmid = 20425514 | doi = 10.1007/s11882-009-0082-6 }}</ref><ref>{{cite journal | vauthors = Custovic A, Simpson A | title = The role of inhalant allergens in allergic airways disease | journal = Journal of Investigational Allergology & Clinical Immunology | volume = 22 | issue = 6 | pages = 393–401; qiuz follow 401 |year=2012 | pmid = 23101182 }}</ref> Efforts to decrease dust mites have been found to be ineffective on symptoms in sensitized subjects.<ref name=Gotzsche2008/><ref>{{cite journal | vauthors = Calderón MA, Linneberg A, Kleine-Tebbe J, De Blay F, Hernandez Fernandez de Rojas D, Virchow JC, Demoly P | title = Respiratory allergy caused by house dust mites: What do we really know? | journal = The Journal of Allergy and Clinical Immunology | volume = 136 | issue = 1 | pages = 38–48 | date = July 2015 | pmid = 25457152 | doi = 10.1016/j.jaci.2014.10.012 | doi-access = free }}</ref> Weak evidence suggests that efforts to decrease mould by repairing buildings may help improve asthma symptoms in adults.<ref>{{cite journal | vauthors = Sauni R, Verbeek JH, Uitti J, Jauhiainen M, Kreiss K, Sigsgaard T | title = Remediating buildings damaged by dampness and mould for preventing or reducing respiratory tract symptoms, infections and asthma | journal = The Cochrane Database of Systematic Reviews | volume = 2015 | issue = 2 | pages = CD007897 | date = February 2015 | pmid = 25715323 | pmc = 6769180 | doi = 10.1002/14651858.CD007897.pub3 }}</ref> Certain viral respiratory infections, such as [[respiratory syncytial virus]] and [[rhinovirus]],<ref name=M38/> may increase the risk of developing asthma when acquired as young children.<ref name=NHLBI07p11>{{harvnb|NHLBI Guideline|2007|p=11}}</ref> Certain other infections, however, may decrease the risk.<ref name=M38/>

====Hygiene hypothesis====
The [[hygiene hypothesis]] attempts to explain the increased rates of asthma worldwide as a direct and unintended result of reduced exposure, during childhood, to non-pathogenic bacteria and viruses.<ref>{{cite journal | vauthors = Ramsey CD, Celedón JC | title = The hygiene hypothesis and asthma | journal = Current Opinion in Pulmonary Medicine | volume = 11 | issue = 1 | pages = 14–20 | date = January 2005 | pmid = 15591883 | doi = 10.1097/01.mcp.0000145791.13714.ae | s2cid = 44556390 }}</ref><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 = 247–62, v–vi | date = May 2005 | pmid = 15878454 | doi = 10.1016/j.iac.2005.03.005 }}</ref> It has been proposed that the reduced exposure to bacteria and viruses is due, in part, to increased cleanliness and decreased family size in modern societies.<ref name=Brook2013>{{cite journal | vauthors = Brooks C, Pearce N, Douwes J | title = The hygiene hypothesis in allergy and asthma: an update | journal = Current Opinion in Allergy and Clinical Immunology | volume = 13 | issue = 1 | pages = 70–7 | date = February 2013 | pmid = 23103806 | doi = 10.1097/ACI.0b013e32835ad0d2 | s2cid = 23664343 }}</ref> Exposure to bacterial [[endotoxin]] in early childhood may prevent the development of asthma, but exposure at an older age may provoke bronchoconstriction.<ref>{{cite journal | vauthors = Rao D, Phipatanakul W | title = Impact of environmental controls on childhood asthma | journal = Current Allergy and Asthma Reports | volume = 11 | issue = 5 | pages = 414–20 | date = October 2011 | pmid = 21710109 | pmc = 3166452 | doi = 10.1007/s11882-011-0206-7 }}</ref> Evidence supporting the hygiene hypothesis includes lower rates of asthma on farms and in households with pets.<ref name=Brook2013/>

Use of [[antibiotic]]s in early life has been linked to the development of asthma.<ref>{{cite journal | vauthors = Murk W, Risnes KR, Bracken MB | title = Prenatal or early-life exposure to antibiotics and risk of childhood asthma: a systematic review | journal = Pediatrics | volume = 127 | issue = 6 | pages = 1125–38 | date = June 2011 | pmid = 21606151 | doi = 10.1542/peds.2010-2092 | s2cid = 26098640 }}</ref> Also, delivery via [[caesarean section]] is associated with an increased risk (estimated at 20–80%) of asthma&nbsp;– this increased risk is attributed to the lack of healthy bacterial colonization that the newborn would have acquired from passage through the birth canal.<ref>{{harvnb|British Guideline|2009|p=72}}</ref><ref name="pmid21645799">{{cite journal | vauthors = Neu J, Rushing J | title = Cesarean versus vaginal delivery: long-term infant outcomes and the hygiene hypothesis | journal = Clinics in Perinatology | volume = 38 | issue = 2 | pages = 321–31 | date = June 2011 | pmid = 21645799 | pmc = 3110651 | doi = 10.1016/j.clp.2011.03.008 }}</ref> There is a link between asthma and the degree of affluence which may be related to the hygiene hypothesis as less affluent individuals often have more exposure to bacteria and viruses.<ref name="pmid14763924">{{cite journal | vauthors = Von Hertzen LC, Haahtela T | title = Asthma and atopy – the price of affluence? | journal = Allergy | volume = 59 | issue = 2 | pages = 124–37 | date = February 2004 | pmid = 14763924 | doi = 10.1046/j.1398-9995.2003.00433.x | s2cid = 34049674 | doi-access = free }}</ref>