Asthma Management Handbook

Considering allergen avoidance where feasible

Recommendations

Advise patients who are at risk of thunderstorm asthma to:

  • check grass pollen counts for their region during spring and early summer (if available)
  • on high grass pollen days, avoid exposure to outdoor air when a thunderstorm is approaching, especially during wind gusts just before the rain front hits (e.g. by going indoors with windows closed and air conditioner off or on recirculation mode, or shutting car windows and recirculating air).

Notes: People with asthma are particularly at risk of thunderstorm asthma if they have seasonal (springtime) allergic rhinitis (i.e. allergic to ryegrass pollen), and live in or are travelling to an area with high grass pollen levels.

People without known asthma (or previous symptoms of asthma) who have springtime allergic rhinitis and are sensitised to allergy to ryegrass pollen are also at risk of thunderstorm asthma.

Pollen counts are available during spring and summer (dates vary) for Melbourne, Sydney, Brisbane, Canberra, Adelaide and Tasmania. Phone apps are available for some areas.

How this recommendation was developed

Adapted from existing guidance

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

  • NACA, 20171

Last reviewed version 2.0

Advise allergen avoidance or reduction measures only if all the following apply:

  • the patient has proven sensitivity to the allergen
  • the allergen is a clinically significant asthma trigger
  • the patient or carer is motivated to apply reduction measures long term and can afford them.

Note: With the exception of thunderstorm asthma prevention measures, which should be advised for all at-risk patients who are living in or travelling to a region with high grass pollen levels.

How this recommendation was developed

Consensus

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

Advise patient or parents that single interventions to reduce exposure to house dust mites are unlikely to be effective in improving asthma symptoms or control.

How this recommendation was developed

Evidence-based recommendation (Grade C)

Based on systematic literature review.

Clinical question for literature search:

Is allergen avoidance effective in improving asthma control? Which allergen avoidance strategies are most effective in controlling symptoms of asthma?

Key evidence considered:

  • Gøtzsche and Johansen, 20082
  • van den Bemt et al. 20073
  • Brehler and Kniest, 20064

Advise patient or parents that a combination of allergen reduction strategies may improve asthma symptoms or control for some patients sensitised to house dust mites.

How this recommendation was developed

Evidence-based recommendation (Grade C)

Based on systematic literature review.

Clinical question for literature search:

Is allergen avoidance effective in improving asthma control? Which allergen avoidance strategies are most effective in controlling symptoms of asthma?

Key evidence considered:

  • Gøtzsche and Johansen, 20082
  • Hayden et al. 19975

Explain that the 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.

How this recommendation was developed

Evidence-based recommendation (Grade C)

Based on systematic literature review.

Clinical question for literature search:

Is allergen avoidance effective in improving asthma control? Which allergen avoidance strategies are most effective in controlling symptoms of asthma?

Key evidence considered:

  • Dorward et al. 19886
  • Hayden et al. 19975
  • Shapiro et al. 19997
  • Walshaw and Evans, 19868

If a person has proven allergy to an animal, and symptoms that correlate with exposure to the particular animal, advise avoidance of the animal. If it is not possible to avoid the animal, consider premedicating with an antihistamine 20–30 minutes before predicted exposure.

How this recommendation was developed

Consensus

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

If the trigger animal is a family pet, advise removal of the pet from the home. If this is not feasible, advise keeping the pet outside or in a limited part of the house, and not allowing the pet into the allergic person’s bedroom.

How this recommendation was developed

Consensus

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

Advise patients who are sensitised to pollens (or parents) that some people try pollen avoidance measures during pollen season, but there is no reliable evidence that these are effective. 

Strategies that may be helpful include:

  • staying indoors during and after thunderstorms 
  • staying indoors on high-pollen days and windy days, if possible
  • wearing sunglasses (which may help prevent allergens from depositing onto the conjunctivae)
  • washing and drying clothing inside to help prevent deposition of pollen allergen on clean clothes
  • keeping windows closed where possible.
How this recommendation was developed

Consensus

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

Advise patients or parents to focus mould avoidance measures on reducing or preventing dampness of the home to prevent mould growth.

How this recommendation was developed

Based on selected evidence

Based on a limited structured literature review or published systematic review, which identified the following relevant evidence:

  • Sauni et al. 20119

More information

Thunderstorm asthma

Certain types of thunderstorms in spring or early summer in regions with high grass pollen concentrations in the air can cause life-threatening allergic asthma flare-ups in individuals sensitised to rye grass, even if they have not had asthma before.3,5,6,8,9

Sensitisation to rye grass allergen is almost universal in patients who have reported flare-ups consistent with thunderstorm asthma in Australia.

People with allergic rhinitis and allergy to ryegrass pollen (i.e. most people with springtime allergic rhinitis symptoms) are at risk of thunderstorm asthma if they live in, or are travelling to, a region with seasonal high grass pollen levels – even if they have never had asthma symptoms before. This includes people with undiagnosed asthma, no previous asthma, known asthma.3, 5 Lack of inhaled corticosteroid preventer treatment has been identified as a risk factor.3

Epidemics of thunderstorm asthma can occur when such a storm travels across a region and triggers asthma in many susceptible individuals. Epidemic thunderstorm asthma events are uncommon, but when they occur can they make a high demand on ambulance and health services.1, 9, 10

Data from thunderstorm asthma epidemics suggest that the risk of asthma flare-ups being triggered by a thunderstorm is highest in adults who are sensitised to grass pollen and have seasonal allergic rhinitis (with or without known asthma).3

The worst outcomes are seen in people with poorly controlled asthma.1 Treatment with an inhaled corticosteroid asthma preventer was significantly protective in a well-conducted Australian case-control study.5

There is insufficient evidence to determine whether intranasal corticosteroids help protect against thunderstorm asthma. Intranasal corticosteroids reduce symptoms of allergic rhinitis and limited indirect evidence suggests they may protect against asthma flare-ups in people not taking inhaled corticosteroids.11

The effectiveness of specific allergen immunotherapy in protecting against thunderstorm asthma has not been evaluated in randomised clinical trials, but data from a small Australian open-label study suggest that short-term treatment with five-grass sublingual immunotherapy may have been protective in individuals.4

Last reviewed version 2.0

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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.10

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;10 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.10 ASCIA’s manual on skin prick testing lists other risk factors.10

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House dust mite

Exposure to house dust mite (mainly Dermatophagoides pteronyssinus) is a major asthma trigger in Australia.11 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:11

  • 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.1213141516617181920214 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.2 The use of allergen-impermeable mattress covers, as a single mite-reduction intervention in adults, is unlikely to be effective in improving asthma.22

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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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.11

The amount of allergen excreted differs between breeds.11 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.11

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.11

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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Pollens

Allergy to airborne pollen grains from certain grasses, weeds and trees is common in people with asthma in Australia.11 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:11, 26

  • 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:11

  • 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.9 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.9 In children living in mouldy houses, remediation of the home may reduce symptoms and flare-ups, compared with cleaning advice about moulds.27

Other strategies that have been proposed for avoiding exposure to moulds include:11

  • 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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Multi-allergen avoidance strategies

Studies assessing interventions designed to reduce exposure to multiple allergens, including studies of individualised allergen avoidance advice after allergy testing, have reported inconsistent findings.28293031

A non-blinded randomised controlled clinical trial in 937 children with allergic asthma reported small reductions in symptoms and emergency department visits during a 1-year multi-component intervention and over a follow-up year, compared with no intervention. The intervention involved a combination of environmental tobacco smoke avoidance with a range of allergen avoidance strategies tailored to the child’s sensitisation profile, including measures to reduce exposure to dust mites (allergen-impermeable covers for mattresses, pillows and bed springs, provision of high-efficiency particulate air-filter vacuum cleaner, installation of high-efficiency particulate air-filter in child’s bedroom), cockroaches (professional pest control), pets (high-efficiency particulate air-filter in child’s bedroom), rodents, and moulds.30

A single-blinded randomised controlled clinical trial in 214 adults with asthma reported an increase in lung function among patients who underwent individualised allergen avoidance, compared with the control group.28

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References

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  22. Valovirta, E., Petersen, T. H., Piotrowska, T., et al. Results from the 5-year SQ grass sublingual immunotherapy tablet asthma prevention (GAP) trial in children with grass pollen allergy. J Allergy Clin Immunol. 2018; 141: 529-538.e13. Available from: https://www.ncbi.nlm.nih.gov/pubmed/28689794
  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
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  28. Karimi, M, Mirzaei, M, Ahmadieh, M H. Acetaminophen use and the symptoms of asthma, allergic rhinitis and eczema in children. Iran J Allergy Asthma Immunol. 2006; 5: 63-67.
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  30. Normansell, R, Walker, S, Milan, S J, et al. Omalizumab for asthma in adults and children. Cochrane Database Syst Rev. 2014; Issue 1: Art. No.: CD003559. Available from: https://www.ncbi.nlm.nih.gov/pubmed/24414989
  31. Andersen, A. B., Erichsen, R., Farkas, D. K., et al. Prenatal exposure to acid-suppressive drugs and the risk of childhood asthma: a population-based Danish cohort study. Aliment Pharmacol Ther. 2012; 35: 1190-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/22443179