Year : 2019 | Volume
: 33 | Issue : 1 | Page : 4--7
Environmental triggers in allergic diseases: An overview
Emeritus Scientist (Former), CSIR-Institute of Genomics and Integrative Biology, Delhi University Campus, Delhi, India
Dr. A B Singh
Emeritus Scientist (Former), CSIR-Institute of Genomics and Integrative Biology, Delhi University Campus, Delhi - 110 007
Allergy and asthma are increasing all over the world including India. The most effective method of management of allergic diseases is prevention and avoidance where ever possible natural history of allergy is influenced by many triggering Biological and non biological agents. Identification of these triggers such as pollen, moulds, mites and insect debris etc., are major factors for secondary prevention of environmental allergens. It is suggested in this brief review that educational programs should focus on avoidance of these triggers for effective management in addition to other forms of therapy.
|How to cite this article:|
Singh A B. Environmental triggers in allergic diseases: An overview.Indian J Allergy Asthma Immunol 2019;33:4-7
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Singh A B. Environmental triggers in allergic diseases: An overview. Indian J Allergy Asthma Immunol [serial online] 2019 [cited 2019 Oct 19 ];33:4-7
Available from: http://www.ijaai.in/text.asp?2019/33/1/4/260178
Epidemiological and experimental studies have contributed to major advances in the field of allergy diagnosis; prevention of allergic diseases. A variety of risk factors play a multifaceted role, in the secondary prevention of allergy. Identification of allergy triggers forms the actual basis of secondary environmental prevention. These triggers include both indoor allergens such as house dust mites (HDMs), molds, pets, and cockroaches and outdoor allergens such as pollen grains, melds, and plant debris. Molds and their metabolites are considered to be triggers of respiratory allergy. Pets, dogs, and cats are well-known to trigger allergic symptoms in sensitized participants. Outdoor molds may trigger allergy and asthma exacerbations. Among outdoor allergens, pollens are important triggers of seasonal allergy symptoms such as allergic rhinitis, atopic dermatitis, and asthma.
House dust mites allergens
HDM allergens are ubiquitous pyroglyphidae that are commonly found in human dwellings. These mites grow best with higher indoor humidity and elevated temperatures. Involvement of mites as triggers of allergy and asthma includes an association between HDM allergen exposure and patients., There have been several studies on avoidance procedures with respect to mite allergens., Four meta-analyses on HDM allergen avoidance by Platts Mills concluded that avoidance was of no benefit to asthmatic/allergic patients. Further, Custovic and Wijk concluded inadequate evidence to advocate avoidance in adults but have some benefit in children. However, Platt-Mills criticized the method of meta-analysis as allergen avoidance protocols are multipronged and personalized. Dusts collected from the houses of patients include many more contaminants besides mites as molds, bacteria, endotoxins, fungal glucans, mycotoxins, pollen, and insect-derived materials, etc.
Thus, house dust avoidance procedures aimed directly on HDMs may only provide partial benefit to sensitized patients.
Molds (Fungi) avoidance
Among indoor triggers, fungi or molds are important microorganisms in patients' dwellings. Although there are thousands of fungal species, avoidance to 60–80 molds are considered allergenically important. There is direct association between dampness and mold proliferation leading to health impacts. The association between dampness and molds in houses has been reviewed by Cox Gamser. In the UK randomized controlled study, allergy symptoms and medications use declined in an interventional group as compared to control group.
Avoidance to pets
It is estimated that ~50% of families in developed countries have pets,,, so is the case of families with allergies. Cats are important triggers of allergic symptoms., Allergy to pets can be readily documented based on the clinical history. Allergic particles from pets are small ranging from 2 to 10 μ size which allows them to be airborne and even stick to cloths of sensitized subjects and floors. Although removal of cats from patients have may minimize their exposure, but may encounter from other locations as it is ubiquitous., When the cast remains in the house, basic avoidance measures do not help in decrease of pet allergen levels.,
Dog allergens are found in the dog hairs, skin cells, saliva, and urine. Dog allergy is less common as compared to cats, and avoidance measures do not help much.
Cockroach allergens are mostly found in kitchen with low- and middle-class houses. Allergy and asthma are associated with cockroach allergen exposure. It is observed that strategies that reduce cockroach allergen by environmental management are clinically beneficial to patients., A joint task force on environmental management of cockroaches has recently been summarized by major professional organizations. The environmental measures include clean kitchens, timely washing of utensils, keeping food items in closed containers, frequent disposal of garbage, setting of cockroach traps, and chemicals and sprays, etc.
Environmental management of pollen is relevant during their pollen season, particularly that are airborne and are important as allergens. During the pollen period, patients are advised to (if possible) to be outdoor during early morning before sunrise and during the late afternoon., In addition to this, door and home windows should be kept shut to reduce pollen exposure from air. Patients are further advised to use air-conditioner, use pollen mask, and use showers after coming from outdoors., Patients also advised to cover their hairs for a long period during outdoors. Although there are common suggestions to minimize pollen exposure, these have not been validated scientifically.
Some of the fungi considered allergenically important as outdoor allergens are Alternaria, Cladosporium, and Fusarium. However, some of the aerophilic species such as Pennicillium and Aspergillus are indoor allergens causing allergic diseases. Compared to indoor allergens, the diagnosis of outdoor mold allergy is difficult due to nonavailability of standardized mold allergen extracts. These fungi also have greater cross-reactivity with even taxonomically unrelated species.
It is well-established that passive smoking is associated with aggravation of asthma and allergy with increased hospitalization. The implementation of public ban on smoking has been observed to have reduced exacerbation of asthma. A meta-analysis of 11 studies published between 2008 and 2013 reported 10% of reduction in hospital admission after smoke ban.
Avoidance of outdoor air pollution is very hard to achieve because there is no realistic way for avoidance their exposure. In children with moderate asthma/allergy have decreased the lung function. Many regulatory agencies recommend that allergic patients may remain indoors during high pollution to avoid exposure to clinical and organic volatile substances. However, some believe indoor air pollution is also equally harmful to susceptible individuals.
When air quality index reaches certain harmful level, all patients should avoid outdoor exposure and reduce the time in outdoor air. Many organizations recommend wearing dust mask and taking antioxidants which may not be very effective., Therefore, sustained clean air remains the most effective way to reduce health effects of respiratory allergy patients that are pollutant related.
In general, the effect of cold temperature triggers asthma symptoms and hospital visit, so is the ease of increasing temperature and increase in emergency visits, particularly by elderly patients. High altitude has been well known to be associated with reduced mite exposure leading to reduced sensitization rate to mites. However, recent studies suggest that reduced allergy in high altitude could be due to overall reduction of pollen and molds leading to reduced exposure of outdoor allergens.
Stress and emotional constraints
Stress enhances the airway inflammation by modulating immune cell function. Psychological triggers have been consistently associated with exacerbation and emergency visits. Anxiety may exacerbate the effects of disrupted steep on childhood asthma.
Recommendation from professional organizations
Recommendation by National Societies in the identification and managements of triggers vary widely. The US guidelines for management of allergy and asthma suggest trigger identification and avoidance instructions. The British Thoracic Society also recommends the identification of triggers and emphasize on the role of passive smoking. The French Society of Pulmonology provides a list of triggers. The American Academy of Allergy also recommends avoiding triggers.
However, with respect to allergen avoidance, there are discrepancies in their recommendations. The British Society does not recommend the use of physical and clinical methods for reducing HDM allergen levels in the home and concludes that single interventions have very limited or no effect. However, the British Society of Allergy and Clinical Immunology advocates that avoidance of HDM may be beneficial in highly motivated allergy patients with multiple interventions. The Allergic Rhinitis and its Impact on Asthma guidelines suggested not using single clinical or physical preventing method of avoidance but to use combinations.
To summarize, the natural history of allergy and asthma are influenced by many triggers of allergenic and nonallergenic origin. Educational programs should focus on patient's questions to address triggers. In many situations, the avoidance of triggers does not provide guarantee for success and multifaceted approach. It must be adopted in avoidance strategies.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
|1||Gent JF, Belanger K, Triche EW, Bracken MB, Beckett WS, Leaderer BP. Association of pediatric asthma severity with exposure to common household dust allergens. Environ Res 2009;109:768-74.|
|2||Gent JF, Kezik JM, Hill ME, Tsai E, Li DW, Leaderer BP. Household mold and dust allergens: Exposure, sensitization and childhood asthma morbidity. Environ Res 2012;118:86-93.|
|3||Hammarquist C, Burr ML, Gotzsche PC. House dust mite control measures for asthma. Cochrane Database Syst Rev2008;2:CD001187.|
|4||Platts-Mills TA. Allergen avoidance in the treatment of asthma: Problems with the meta-analyses. J Allergy Clin Immunol 2008;122:694-6.|
|5||Custovic A, Wijk RG. The effectiveness of measures to change the indoor environment in the treatment of allergic rhinitis and asthma: ARIA update (in collaboration with GA (2) LEN). Allergy 2005;60:1112-5.|
|6||Nevalainen A, Täubel M, Hyvärinen A. Indoor fungi: Companions and contaminants. Indoor Air 2015;25:125-56.|
|7||Cox-Ganser JM. Indoor dampness and mould health effects – Ongoing questions on microbial exposures and allergic versus nonallergic mechanisms. Clin Exp Allergy 2015;45:1478-82.|
|8||American Pet Products Association. National Pet Owners Survey, 2009-2010. Available from: http://www.pfma.com/faq.html. [Last accessed on 2016 Nov 07].|
|9||The European Pet Food Industry Federation. Facts and Figures; 2012. Available from: http://www.fediaf.org/fileadmin/user_upload/facts_and_figures_2010.pdf. [Last accessed on 2016 Nov 07].|
|10||Pyrhönen K, Näyhä S, Läärä E. Dog and cat exposure and respective pet allergy in early childhood. Pediatr Allergy Immunol 2015;26:247-55.|
|11||Ritz BR, Hoelscher B, Frye C, Meyer I, Heinrich J. Allergic sensitization owing to 'second-hand' cat exposure in schools. Allergy 2002;57:357-61.|
|12||Enberg RN, Shamie SM, McCullough J, Ownby DR. Ubiquitous presence of cat allergen in cat-free buildings: Probable dispersal from human clothing. Ann Allergy 1993;70:471-4.|
|13||Karlsson AS, Renström A, Hedrén M, Larsson K. Allergen avoidance does not alter airborne cat allergen levels in classrooms. Allergy 2004;59:661-7.|
|14||de Blay F, Chapman MD, Platts-Mills TA. Airborne cat allergen (Fel d I). Environmental control with the cat in situ. Am Rev Respir Dis 1991;143:1334-9.|
|15||Rosenstreich DL, Eggleston P, Kattan M, Baker D, Slavin RG, Gergen P, et al. The role of cockroach allergy and exposure to cockroach allergen in causing morbidity among inner-city children with asthma. N Engl J Med 1997;336:1356-63.|
|16||National Asthma Education and Prevention Program. Expert panel report 3 (EPR-3): Guidelines for the diagnosis and management of asthma-summary report 2007. J Allergy Clin Immunol 2007;120:S94-138.|
|17||Morgan WJ, Crain EF, Gruchalla RS, O'Connor GT, Kattan M, Evans R 3rd, et al. Results of a home-based environmental intervention among urban children with asthma. N Engl J Med 2004;351:1068-80.|
|18||Office of Environmental Health Hazard Assessment. Health Effects of Exposure to Environmental Tobacco Smoke, Final Report. Sacramento, CA: EPA; 2005. Available from: http://www. 0ehha.ca.gov/air/report/health-effects-exposure-environmental-tobacco-smoke-fingal-report. [Last accessed on 2016 Nov 07].|
|19||Mackay D, Haw S, Ayres JG, Fischbacher C, Pell JP. Smoke-free legislation and hospitalizations for childhood asthma. N Engl J Med 2010;363:1139-45.|
|20||Zhang S, Li L, Gao W, Wang Y, Yao X. Interventions to reduce individual exposure of elderly individuals and children to haze: A review. J Thorac Dis 2016;8:E62-8.|
|21||Kim J, Lim Y, Kim H. Outdoor temperature changes and emergency department visits for asthma in Seoul, Korea: A time-series study. Environ Res 2014;135:15-20.|
|22||22 Ozkaya E, Sogut A, Küçükkoç M, Eres M, Acemoglu H, Yuksel H, et al. Sensitization pattern of inhalant allergens in children with asthma who are living different altitudes in Turkey. Int J Biometeorol 2015;59:1685-90.|
|23||Daniel LC, Boergers J, Kopel SJ, Koinis-Mitchell D. Missed sleep and asthma morbidity in urban children. Ann Allergy Asthma Immunol 2012;109:41-6.|
|24||Camargo CA Jr., Rachelefsky G, Schatz M. Managing asthma exacerbations in the emergency department: Summary of the national asthma education and prevention program expert panel report 3 guidelines for the management of asthma exacerbations. Proc Am Thorac Soc 2009;6:357-66.|
|25||Guidelines. British Guidelines on the Management of Asthma in Audlts. Available from: http://www.guidelines.co.uk/btssign/asthma-in-adult. [Last accessed on 2016 Nov 07].|
|26||Raherison C, Bourdin A, Bonniaud P, Deslée G, Garcia G, Leroyer C, et al. Updated guidelines (2015) for management and monitoring of adult and adolescent asthmatic patients (from 12 years and older) of the société de pneumologie de langue Française (SPLF) (summary). Rev Mal Respir 2016;33:271-8.|
|27||American College of Chest Physician and the Chest Foundation. Controlling Your Asthma. Available from: http://www.med.umich.edu/1info/FHP/practiceguides/asthma/chestpt.pdf. [Last accessed on 2016 Nov 07].|
|28||Scadding GK, Durham SR, Mirakian R, Jones NS, Leech SC, Farooque S, et al. BSACI guidelines for the management of allergic and non-allergic rhinitis. Clin Exp Allergy 2008;38:19-42.|
|29||Brozek JL, Bousquet J, Baena-Cagnani CE, Bonini S, Canonica GW, Casale TB, et al. Allergic rhinitis and its impact on asthma (ARIA) guidelines: 2010 revision. J Allergy Clin Immunol 2010;126:466-76.|