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Asthma - Management
Allergen avoidance: What advice should I give someone with asthma?

  • Advise all people with asthma and parents looking after children with asthma to avoid (if possible) known trigger factors, especially at times when asthma is poorly controlled.
  • Advise all adults to report promptly any worsening asthma control during work.
Clarification / Additional information
  • The person with asthma should identify trigger factors, where possible, by noting worsening symptoms or decreasing peak expiratory flow rates (PEFR) during exposure to certain situations. Some triggers cannot be avoided (e.g. air pollution, weather, viral illness), but at times of poor asthma control, it is prudent to do so if possible. Uncontrolled asthma is more sensitive to possible trigger factors.
  • Dust mites: sensitization to house dust mite is an important risk factor for the development of asthma, however in the absence of benefit from domestic aeroallergen avoidance, it is not possible to recommend it as a strategy for preventing childhood asthma. Overall, measures to decrease house dust mites have not been shown to have an effect on asthma severity. If a household member shows evidence of house dust mite allergy and wishes to try mite avoidance, strategies include complete barrier bed-covering systems, ensuring that susceptible children do not sleep in a lower bunk bed, removal of carpets or soft toys from beds, high-temperature washing of bed linen, application of acaricides (chemical agents that kill mites) to soft furnishings, and good ventilation.
  • Animal allergens, particularly cat and dog allergens, are potent inducers of asthma symptoms. Many experts recommend the removal of pets from the home of allergic people with asthma, but the reported effects are inconsistent.
  • Food and food additives (e.g. sulphites found in wine, beer, processed potatoes, shrimps) as an exacerbating factor for asthma are uncommon and occur primarily in young children. Do not recommend food avoidance unless there is a proven allergy, and then only with the supervision of a dietitian, especially in children.
  • Air pollutants (ozone, nitrogen oxide, acidic aerosols) and occasional weather changes have been associated with asthma symptoms and exacerbations, although there is no evidence to support a link between exposure to air pollutants and the induction of allergy. There is no need to recommend avoidance in people with stable asthma. Advise people with poorly controlled asthma who are troubled by outdoor triggers to minimize exposure, such as by not doing strenuous exercise or smoking in cold weather, low humidity, or times of high air pollution.
  • An occupational trigger will usually worsen asthma at work, and improvements will occur when the person is away from the work environment. Identify people with occupational triggers early and refer them to a respiratory specialist.
Basis for recommendation
  • These recommendations are based on the British Guideline on the Management of Asthma: a national clinical guideline [SIGN and BTS, 2009]:
    • Allergen avoidance: the evidence that reducing allergen exposure can reduce morbidity and mortality is tenuous. In uncontrolled studies, children and adults have shown some benefit from exposure to very-low-allergen environments. However, the benefits cannot be necessarily attributed to allergen avoidance. Larger, well-designed studies of combined-allergen avoidance strategies in different groups are needed [GINA, 2006; SIGN and BTS, 2009].

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