Asthma Management Handbook

Assessing allergies to guide asthma management

Recommendations

When taking a history in a patient with suspected asthma, ask about allergies, and the circumstances and timing of symptoms.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

When performing a physical examination in a patient with suspected asthma, inspect the upper airway for signs of allergic rhinitis (e.g. swollen turbinates, transverse nasal crease, reduced nasal airlfow, mouth breathing, darkness and swelling under eyes caused by sinus congestion).

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

Consider allergy testing as part of diagnostic investigations if you suspect allergic triggers, or to guide management.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

Consider allergy tests for children with recurrent wheezing when the results might guide you in (either of):

  • assessing the prognosis (e.g. in preschool children, the presence of allergies increases the probability that the child will have asthma at primary school age)
  • managing symptoms (e.g. advising parents about management if avoidable allergic triggers are identified).

Note: Allergy tests are not mandatory in the diagnostic investigation of asthma in children.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

If allergy testing is needed, refer to an appropriate provider for skin prick testing for common aeroallergens.

Notes

If staff are trained in the skin prick test procedure and its interpretation, skin prick testing can be performed in primary care. If not, refer to an appropriate provider.

When performing skin prick testing, follow Australasian Society of Clinical Immunology and Allergy (ASCIA) guidance: Skin prick testing for the diagnosis of allergic disease. A manual for practitioners

How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s):

  • Australasian Society of Clinical Immunology and Allergy, 20131

Blood test (immunoassay for allergen-specific immunoglobulin E) can be used if skin prick testing is (any of):

  • unavailable
  • impractical (e.g. a patient who is unable to cooperate with test procedure, a patient taking antihistamines when these cannot be withdrawn, or a patient taking tricyclic antidepressants or pizotifen)
  • contraindicated (e.g. patients with severe dermatographism, extensive skin rash, or those at risk of anaphylaxis including patients with occupational asthma due to latex sensitivity).
How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s):

  • Australasian Society of Clinical Immunology and Allergy, 20131

To investigate allergies in a person with severe or unstable asthma, or a history of anaphylaxis, refer to a specialist allergist for investigation to minimise risk.

How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s):

  • Australasian Society of Clinical Immunology and Allergy, 20131

Consider offering referral to an appropriate specialist (e.g. respiratory physician, occupational physician or allergist) for patients with:

  • suspected or confirmed work-related asthma
  • other significant allergic disease (e.g. suspected food allergies or severe eczema).
How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

If patients are likely to visit practitioners who offer alternative diagnostic tests, explain that none of the following alternative diagnostic practices should be used in the diagnosis of asthma or allergies:

  • cytotoxic testing (Bryans’ or Alcat testing)
  • hair analysis
  • iridology
  • kinesiology
  • oral provocation and neutralisation
  • pulse testing
  • radionics (psionic medicine, dowsing)
  • tests for ‘dysbiosis’
  • vega testing (electrodermal testing)
  • VoiceBio.
How this recommendation was developed

Adapted from existing guidance

Based on reliable clinical practice guideline(s) or position statement(s):

  • Australasian Society of Clinical Immunology and Allergy, 20072

More information

Allergies and asthma: links

There is a strong link between asthma and allergies:3, 4

  • The majority of people with asthma have allergies.
  • Immunoglobulin E-mediated sensitisation to inhalant allergens is an important risk factor for developing asthma, particularly in childhood.
  • In individuals with asthma, exposure to relevant allergens can worsen asthma symptoms and trigger flare-ups, including severe acute asthma.
  • Allergens are a common cause of occupational asthma.

Although atopic sensitisation increases the risk of developing asthma, most people who are allergic to inhalant allergens or food allergens do not have asthma.4 Among people with food allergies, asthma may be a risk factor for fatal anaphylaxis due to food allergens.56 However, foods are rarely a trigger for asthma symtpoms.

Neither asthma nor allergy is a single disease – each has multiple phenotypes and is a complex of several different diseases with different aetiologies, genetic risk factors and environmental risk factors.3

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Allergic rhinitis and asthma: links

Prevalence, aetiology and symptoms

Asthma and allergic rhinitis frequently coexist. At least 75% of patients with asthma also have rhinitis, although estimates vary widely.7

Allergic rhinitis that starts early in life is usually due to a classical IgE hypersensitivity. Adult-onset asthma or inflammatory airway conditions typically have more complex causes. Chronic rhinosinusitis with nasal polyps is not a simple allergic condition and generally needs specialist care.8

Symptoms and signs of allergic rhinitis can be local (e.g. nasal discharge, congestion or itch), regional (e.g. effects on ears, eyes, throat or voice), and systemic (e.g. sleep disturbance and lethargy). Most people with allergic rhinitis experience nasal congestion or obstruction as the predominant symptom. Ocular symptoms (e.g. tearing and itch) in people with allergic rhinitis are usually due to coexisting allergic conjunctivitis.9

Patients may mistake symptoms of allergic rhinitis for asthma. Allergic rhinitis is sometimes more easily recognised only after asthma has been stabilised.

Effects on asthma

The presence of allergic rhinitis is associated with worse asthma control in children and adults.10111213

Both rhinitis and asthma can be triggered by the same factors, whether allergic (e.g. house dust mite, pet allergens, pollen, cockroach) or non-specific (e.g. cold air, strong odours, environmental tobacco smoke). Food allergies do not cause allergic rhinitis. Most people with allergic rhinitis are sensitised to multiple allergens (e.g. both pollens and house dust mite), so symptoms may be present throughout the year. Pollens (e.g. grasses, weeds, trees) and moulds are typically seasonal allergens in southern regions, but can be perennial in tropical northern regions.8 Pollen calendars provide information on when airborne pollen levels are likely to be highest for particular plants.

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Allergic rhinitis and asthma: treatment

Intranasal corticosteroids

Intranasal corticosteroids are effective in reducing congestion, rhinorrhoea, sneezing and itching in adults and children with allergic rhinitis,7 and are also effective against ocular symptoms associated with allergic rhinitis.7, 14, 15 Intranasal corticosteroids are more effective in reducing nasal symptoms than other treatments,7, 14 including oral H1-antihistamines14, 16 and montelukast,7, 14 and are at least as effective as intranasal H1-antihistamines.7, 16 The use of intranasal corticosteroids in patients with concomitant allergic rhinitis and asthma may improve asthma control.1417

Intranasal corticosteroids are generally well tolerated in long-term use. In patients with asthma already taking inhaled corticosteroids, the intranasal corticosteroid dose should be taken into account when determining the total daily corticosteroid dose.

Patients need careful training to use intranasal sprays correctly. Detailed information and instructional videos for health professionals and patients are available on the National Asthma Council Australia website.

Antihistamines

Intranasal antihistamines reduce all symptoms of allergic rhinitis.16 Some have a more rapid onset of action than intranasal corticosteroids.16 Intranasal antihistamines are as effective as newer, less sedating oral H1-antihistamines,7 but are generally less effective than intranasal corticosteroids for the treatment of allergic rhinitis.14

Second-generation, less sedating oral H1-antihistamines (e.g. cetirizine, desloratadine, fexofenadine, levocetirizine or loratadine) are effective in managing allergic rhinitis symptoms of rhinorrhoea, sneezing, nasal itching and ocular symptoms,18 but are less effective for congestion.19 They are also effective for managing co-occurring ocular symptoms of allergy.14, 20

Specific allergen immunotherapy

Specific allergen immunotherapy (desensitisation) is effective in reducing allergic rhinitis symptoms (See separate topic).7, 21

Decongestants

Intranasal decongestants have a limited role in the management of allergic rhinitis because they should only be used for very short courses (up to 5 days maximum). Repeated or long-term use can cause rebound swelling of nasal mucosa necessitating dose escalation (rhinitis medicamentosa), with a risk of atrophic rhinitis.

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Allergy tests in adults with asthma

Allergy tests have a very limited role in the clinical investigation of asthma. They may be useful to guide management if the patient is sensitised to aeroallergens that are avoidable and avoidance has been shown to be effective, or in the investigation of suspected occupational asthma.

The Australasian Society of Clinical Immunology and Allergy (ASCIA) recommends skin prick testing as the first-choice method for investigating allergies in a person with asthma.1

Patients who need allergy tests are usually referred to a specialist for investigation. GPs with appropriate training and experience can also perform skin prick tests for inhalent allergens, if facilities to treat potential systemic allergic reactions are available, or arrange for allergy tests (skin prick testing or blood tests) to be performed by an appropriate provider. Skin prick testing for food allergens should only be performed in specialist practices.

Asthma, particularly uncontrolled or unstable asthma, may be a risk factor for anaphylaxis during skin prick testing;1 however, anaphylaxis due to skin prick testing is extremely rare. As a precaution, ASCIA advises that skin prick testing in people with severe or unstable asthma should be performed only in specialist practices.1 ASCIA’s manual on skin prick testing lists other risk factors.1

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Allergy tests in children

Skin-prick testing

Allergy tests have a very limited role in the clinical investigation of asthma. They may be useful to guide management if the child is sensitised to aeroallergens that are avoidable (e.g. advise parents  against getting a cat if skin-prick testing has shown that the child is sensitised to cat allergens, or advise parents that there is no need to remove a family pet if the child is not sensitised).

Skin-prick testing is the recommended test for allergies in children.

Risk factors for anaphylaxis during skin prick testing are thought to include asthma (particularly uncontrolled or unstable asthma), age less than 6 months, and widespread atopic dermatitis in children.1 As a precaution, the Australasian Society of Clinical Immunology and Allergy (ASCIA) advises that skin prick testing should be performed only in specialist practices for children under 2 years and children with severe or unstable asthma.1 ASCIA’s manual on skin prick testing lists other risk factors.1

Total serum IgE testing

In children aged 0–5 years, total serum immunoglobulin E measurement is a poor predictor of allergies or asthma.22

Specific serum IgE testing

Among children aged 1–4 years attending primary care, those with raised specific IgE for inhaled allergens (e.g. house dust mite, cat dander) are two-to-three times more likely to have asthma at age 6 than non-sensitised children.22 Sensitisation to hen’s egg at the age of 1 year (specific IgE) is a strong predictor of allergic sensitisation to inhaled allergens at age 3 years.22

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Pet allergens

Contact with pets (e.g. cats, dogs and horses) can trigger asthma, mainly due to sensitisation to allergens in sebum or saliva. Exposure can trigger flare-ups or worsen symptoms.3

The amount of allergen excreted differs between breeds.3 Although some breeders claim that certain breeds of dogs are less likely to trigger asthma (‘hypoallergenic’ breeds), allergen levels have not been shown to be lower in the animal’s hair or coat,23 or in owner’s homes24 with these breeds than other breeds.

Cat allergens easily spread on clothing and are found in places where cats have never been.3

The most effective method of allergen avoidance for people with asthma who are allergic to cats or dogs is to not have these pets in the home. However, the allergen can persist for many months, or even years, after the pet has been removed.3

There is not enough clinical trial evidence to determine whether or not air filtration units are effective to reduce allergen levels in the management of pet-allergic asthma.25

Other strategies for reducing exposure to pet allergens include:

  • washing hands and clothes after handling pets
  • washing clothes and pet bedding in hot water  (> 55°C)
  • frequent vacuuming of the home using a vacuum with a HEPA filter
  • cleaning hard floors with a damp/antistatic cloth or a steam mop, and cleaning air-conditioning or heating ducts
  • grooming pets regularly (where possible, the patient should be absent while this occurs), and washing pets regularly, but no more than the vet recommends.
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House dust mite

Exposure to house dust mite (mainly Dermatophagoides pteronyssinus) is a major asthma trigger in Australia.3 These microscopic mites live indoors, feed on skin scales, and thrive in temperate and humid climates such as coastal Australia.

Strategies that have been proposed for reducing exposure to house dust mites include:3

  • encasing bedding (pillows, mattresses and doonas) in mite-impermeable covers
  • weekly washing bed linen (pillow cases, sheets, doona covers) in a hot wash (> 55°C)
  • using pillows manufactured with anti-microbial treatments that suppress fungal growth and dust mites
  • removing unnecessary bedding such as extra pillows and cushions where dust mites might live and breed
  • removing soft toys, or washing them in a hot wash (> 55°C) every week
  • vacuuming rugs and carpets weekly using a vacuum with a high-efficiency particulate air (HEPA) filter, while allergic person is absent
  • cleaning hard floors weekly with a damp or antistatic cloth, mop or a steam mop and dusting weekly using a damp or antistatic cloth
  • regularly washing curtains or replacing curtains with cleanable blinds
  • spraying the area with chemicals that kill mites (acaricides), such as benzyl benzoate spray or liquid nitrogen. Acaricide sprays are not commonly used in Australia.

Some clinical trials assessing the dust mite avoidance strategies (e.g. the use of allergen-impermeable mattress and pillow covers, acaricide sprays, air filters, or combinations of these) have reported a reduction in levels of house dust mite.262728293031323334353637 However, reduced exposure may not improve symptoms.

Overall, clinical trials assessing dust mite avoidance for patients with asthma do not show that these strategies are effective in improving asthma symptoms, improving lung function or reducing asthma medication requirements in adults or children, compared with sham interventions or no interventions.38 The use of allergen-impermeable mattress covers, as a single mite-reduction intervention in adults, is unlikely to be effective in improving asthma.39

Use of mite allergen-impermeable covers for bedding (e.g. mattress covers, pillow covers, doona covers) was a component of some of the multi-component strategies for reducing house dust mite exposure that have been shown to be effective for improving asthma symptoms or control.

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Pollens

Allergy to airborne pollen grains from certain grasses, weeds and trees is common in people with asthma in Australia.3 The highest pollen counts occur on calm, hot, sunny days in spring or early summer, or during the dry season in tropical regions.

Exposure to pollen:3, 40

  • may worsen asthma symptoms during the pollen season
  • can cause outbreaks of asthma flare-ups after thunderstorms
  • is usually caused by imported grasses, weeds and trees (which are wind pollinated) – the pollen can travel many kilometres from its source
  • is not usually caused by Australian native plants (although there are exceptions, such as Cypress Pine)
  • is not usually caused by highly flowered plants as they produce less pollen (which is transported by bees) than wind pollinated plants.

Completely avoiding pollen can be difficult during the pollen season. Strategies that have been proposed for avoiding exposure to pollens include:3

  • avoiding going outdoors on days with high pollen counts (particularly 7–9 am and 4–6 pm), on windy days or after thunderstorms
  • keeping car windows closed, ensuring the vehicle has a pollen cabin air filter and setting the cabin air to recirculate
  • showering (or washing face and hands thoroughly) after being outside with exposure to pollen
  • drying bed linen indoors during the pollen season
  • holidaying out of the pollen season or at the seaside
  • not mowing the grass, and staying inside when it is being mown
  • wearing a facemask and/or glasses in special situations where pollen can’t be avoided, e.g. if mowing is unavoidable
  • removing any plants the patient is sensitive to from their garden.

Daily pollen indices and forecasts are available from news media websites (e.g. www.weatherzone.com.au).

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Moulds

Building repairs to reduce dampness in homes (e.g. leak repair, improvement of ventilation, removal of water-damaged materials) may reduce asthma symptoms and the use of asthma medicines.41 A systematic review and meta-analysis found that damp remediation of houses reduced asthma-related symptoms including wheezing in adults, and reduced acute care visits in children.41 In children living in mouldy houses, remediation of the home may reduce symptoms and flare-ups, compared with cleaning advice about moulds.42

Other strategies that have been proposed for avoiding exposure to moulds include:3

  • removing visible mould by cleaning with bleach or other mould reduction cleaners (patients should avoid breathing vapours)
  • using high-efficiency air filters
  • removing indoor pot plants
  • drying or removing wet carpets
  • treating rising damp as soon as it is detected
  • avoiding the use of organic mulches and compost.
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Triggers in the workplace

A wide range of occupational allergens has been associated with work-related asthma. Investigation of work-related asthma is complex and typically requires specialist referral.

Table. Examples of common sensitising agents and occupations associated with exposure

Agent

Occupations

Low molecular weight agents

Wood dust (e.g. western red cedar, redwood, oak)

  • Carpenters
  • Builders
  • Model builders
  • Sawmill workers
  • Sanders

Isocyanates

  • Automotive industry workers
  • Adhesive workers
  • Chemical industry
  • Mechanics
  • Painters
  • Polyurethane foam production workers

Formaldehyde

  • Cosmetics industry
  • Embalmers
  • Foundry workers
  • Hairdressers
  • Healthcare workers
  • Laboratory workers
  • Tanners
  • Paper, plastics and rubber industry workers

Platinum salts

  • Chemists
  • Dentists
  • Electronics industry workers
  • Metallurgists
  • Photographers

High molecular weight agents

Latex

  • Food handlers
  • Healthcare workers
  • Textile industry workers
  • Toy manufacturers

Flour and grain dust

  • Bakers
  • Combine harvester drivers
  • Cooks
  • Farmers
  • Grocers
  • Pizza makers

Animal allergens (e.g. urine, dander)

  • Animal breeders
  • Animal care workers
  • Jockeys
  • Laboratory workers
  • Pet shop workers
  • Veterinary surgery workers

Source: Adapted from Hoy R, Abramson MJ, Sim MR. Work related asthma. Aust Fam Physician 2010; 39: 39-42. Available from: http://www.racgp.org.au/afp/201001/35841

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Alternative diagnostic tests for asthma and allergy

The Australasian Society of Clinical Immunology and Allergy (ASCIA) recommends against the following techniques for the diagnosis and treatment of allergy, asthma and immune disorders because they have not been shown to be reliable or accurate:2

  • cytotoxic testing (Bryans’ or Alcat testing)
  • hair analysis
  • iridology
  • kinesiology
  • oral provocation and neutralisation
  • pulse testing
  • radionics (psionic medicine, dowsing)
  • tests for ‘dysbiosis’
  • vega testing (electrodermal testing)
  • VoiceBio.

ASCIA also recommends against the use of conventional tests in the investigation of allergies in inappropriate clinical situations, or where the results are presented in a manner amenable to misinterpretation, e.g:2

  • food-specific IgE (RAST, ImmunoCap testing)
  • food-specific IgG, IgG4
  • lymphocyte subset analysis.
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References

  1. Australasian Society of Clinical Immunology and Allergy (ASCIA), Skin Prick Testing Working Party. Skin prick testing for the diagnosis of allergic disease: A manual for practitioners. ASCIA, Sydney, 2013. Available from: http://www.allergy.org.au/health-professionals/papers/skin-prick-testing
  2. Australasian Society of Clinical Immunology and Allergy (ASCIA), ASCIA Position Statement. Unorthodox Techniques for the Diagnosis and Treatment of allergy, Asthma and Immune Disorders, ASCIA 2007. Available from: http://www.allergy.org.au/health-professionals/papers/unorthodox-techniques-for-diagnosis-and-treatment
  3. National Asthma Council Australia. Asthma and allergy. National Asthma Council Australia, Melbourne, 2012. Available from: http://www.nationalasthma.org.au/publication/asthma-allergy-hp
  4. Custovic A, Simpson A. The role of inhalant allergens in allergic airways disease. J Investig Allergol Clin Immunol. 2012; 22: 393-401. Available from: http://www.jiaci.org/issues/vol22issue6/vol22issue06-1.htm
  5. Bock SA, Muñoz-Furlong A, Sampson HA. Fatalities due to anaphylactic reactions to foods. J Allergy Clin Immunol. 2001; 107: 191-3. Available from: http://www.ncbi.nlm.nih.gov/pubmed/11150011
  6. Bock SA, Muñoz-Furlong A, Sampson HA. Further fatalities caused by anaphylactic reactions to food, 2001-2006. J Allergy Clin Immunol. 2007; 119: 1016-1018. Available from: http://www.jacionline.org/article/S0091-6749(06)03814-0/fulltext
  7. Brożek JL, Bousquet J, Baena-Cagnani CE, et al. Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines: 2010 Revision. J Allergy Clin Immunol. 2010; 126: 466-476. Available from: http://www.jacionline.org/article/S0091-6749(10)01057-2/fulltext
  8. National Asthma Council Australia. Managing allergic rhinitis in people with asthma. An information paper for health professionals. National Asthma Council Australia, Melbourne, 2012. Available from: http://www.nationalasthma.org.au/publication/allergic-rhinitis-asthma-hp
  9. Spangler DL, Abelson MB, Ober A, Gotnes PJ. Randomized, double-masked comparison of olopatadine ophthalmic solution, mometasone furoate monohydrate nasal spray, and fexofenadine hydrochloride tablets using the conjunctival and nasal allergen challenge models. Clin Ther. 2003; 25: 2245-67. Available from: http://www.ncbi.nlm.nih.gov/pubmed/14512132
  10. Pawankar R, Bunnag C, Chen Y, et al. Allergic rhinitis and its impact on asthma update (ARIA 2008)–western and Asian-Pacific perspective. Asian Pac J Allergy Immunol. 2009; 27: 237-243. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20232579
  11. de Groot EP, Nijkamp A, Duiverman EJ, Brand PL. Allergic rhinitis is associated with poor asthma control in children with asthma. Thorax. 2012; 67: 582-7. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22213738
  12. Thomas M, Kocevar VS, Zhang Q, et al. Asthma-related health care resource use among asthmatic children with and without concomitant allergic rhinitis. Pediatrics. 2005; 115: 129-34. Available from: http://pediatrics.aappublications.org/content/115/1/129.long
  13. Price D, Zhang Q, Kocevar VS, et al. Effect of a concomitant diagnosis of allergic rhinitis on asthma-related health care use by adults. Clin Exp Allergy. 2005; 35: 282-7. Available from: http://www.ncbi.nlm.nih.gov/pubmed/15784104
  14. Wallace DV, Dykewicz MS, Bernstein DI, et al. The diagnosis and management of rhinitis: An updated practice parameter. J Allergy Clin Immunol. 2008; 122: S1-S84. Available from: http://www.jacionline.org/article/S0091-6749(08)01123-8/fulltext
  15. Hong J, Bielory B, Rosenberg JL, Bielory L. Efficacy of intranasal corticosteroids for the ocular symptoms of allergic rhinitis: A systematic review. Allergy Asthma Proc. 2011; 32: 22-35. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21262095
  16. Kaliner MA, Berger WE, Ratner PH, Siegel CJ. The efficacy of intranasal antihistamines in the treatment of allergic rhinitis. Ann Allergy Asthma Immunol. 2011; 106: S6-s11. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21277531
  17. Kersten ET, van Leeuwen JC, Brand PL, et al. Effect of an intranasal corticosteroid on exercise induced bronchoconstriction in asthmatic children. Pediatr Pulmonol. 2012; 47: 27-35. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22170807
  18. Bachert C, Maspero J. Efficacy of second-generation antihistamines in patients with allergic rhinitis and comorbid asthma. J Asthma. 2011; 48: 965-73. Available from: http://www.ncbi.nlm.nih.gov/pubmed/21970671
  19. Bousquet J, Khaltaev N, Cruz AA, et al. Allergic Rhinitis and its Impact on Asthma (ARIA) 2008. Allergy. 2008; 63: 8-160. Available from: http://onlinelibrary.wiley.com/doi/10.1111/j.1398-9995.2007.01620.x/full
  20. Howarth PH. Assessment of antihistamine efficacy and potency. Clin Exp Allergy. 1999; 29 Suppl 3: 87-97. Available from: http://www.ncbi.nlm.nih.gov/pubmed/10444220
  21. Lin S, Erekosima N, Kim J, et al. Sublingual immunotherapy for the treatment of allergic rhinoconjunctivitis and asthma: A systematic review. JAMA. 2013; 309: 1278-1288. Available from: http://www.ncbi.nlm.nih.gov/pubmed/23532243
  22. Brand PL, Baraldi E, Bisgaard H, et al. Definition, assessment and treatment of wheezing disorders in preschool children: an evidence-based approach. Eur Respir J. 2008; 32: 1096-1110. Available from: http://erj.ersjournals.com/content/32/4/1096.full
  23. Vredegoor DW, Willemse T, Chapman MD, et al. Can f 1 levels in hair and homes of different dog breeds: lack of evidence to describe any dog breed as hypoallergenic. J Allergy Clin Immunol. 2012; 130: 904-9.e7. Available from: http://www.jacionline.org/article/S0091-6749(12)00793-2/fulltext
  24. Nicholas CE, Wegienka GR, Havstad SL, et al. Dog allergen levels in homes with hypoallergenic compared with nonhypoallergenic dogs. Am J Rhinol Allergy. 2011; 25: 252-6. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3680143/
  25. Kilburn S, Lasserson TJ, McKean M. Pet allergen control measures for allergic asthma in children and adults. Cochrane Database Syst Rev. 2001; Issue 1: CD002989. Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD002989/full
  26. de Vries MP, van den Bemt L, Aretz K, et al. House dust mite allergen avoidance and self-management in allergic patients with asthma: randomised controlled trial. Br J Gen Pract. 2007; 57: 184-90. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2042544/
  27. Dharmage S, Walters EH, Thien F, et al. Encasement of bedding does not improve asthma in atopic adult asthmatics. Int Arch Allergy Immunol. 2006; 139: 132-8. Available from: http://www.ncbi.nlm.nih.gov/pubmed/16374022
  28. van den Bemt L, van Knapen L, de Vries MP, et al. Clinical effectiveness of a mite allergen-impermeable bed-covering system in asthmatic mite-sensitive patients. J Allergy Clin Immunol. 2004; 114: 858-62. Available from: http://www.jacionline.org/article/S0091-6749(04)01671-9/fulltext
  29. Cloosterman SG, Schermer TR, Bijl-Hofland ID, et al. Effects of house dust mite avoidance measures on Der p 1 concentrations and clinical condition of mild adult house dust mite-allergic asthmatic patients, using no inhaled steroids. Clin Exp Allergy. 1999; 29: 1336-46. Available from: http://www.ncbi.nlm.nih.gov/pubmed/10520054
  30. van der Heide S, Kauffman HF, Dubois AE, de Monchy JG. Allergen-avoidance measures in homes of house-dust-mite-allergic asthmatic patients: effects of acaricides and mattress encasings. Allergy. 1997; 52: 921-7. Available from: http://www.ncbi.nlm.nih.gov/pubmed/9298177
  31. Dorward AJ, Colloff MJ, MacKay NS, et al. Effect of house dust mite avoidance measures on adult atopic asthma. Thorax. 1988; 43: 98-102. Available from: http://thorax.bmj.com/content/43/2/98.short
  32. Halken S, Host A, Niklassen U, et al. Effect of mattress and pillow encasings on children with asthma and house dust mite allergy. J Allergy Clin Immunol. 2003; 111: 169-76. Available from: http://www.jacionline.org/article/S0091-6749(02)91267-4/fulltext
  33. Frederick JM, Warner JO, Jessop WJ, et al. Effect of a bed covering system in children with asthma and house dust mite hypersensitivity. Eur Respir J. 1997; 10: 361-6. Available from: http://erj.ersjournals.com/content/10/2/361.short
  34. Warner JA, Marchant JL, Warner JO. Double blind trial of ionisers in children with asthma sensitive to the house dust mite. Thorax. 1993; 48: 330-3. Available from: http://thorax.bmj.com/content/48/4/330.abstract
  35. Thiam DG, Tim CF, Hoon LS, et al. An evaluation of mattress encasings and high efficiency particulate filters on asthma control in the tropics. Asian Pac J Allergy Immunol. 1999; 17: 169-74. Available from: http://www.ncbi.nlm.nih.gov/pubmed/10697255
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