Step 3: Maintain Best Lung Function
Identify and Avoid Trigger Factors

 

Allergens

Allergy is a frequent trigger of asthma. Investigating and avoiding allergic factors is recommended. If specific triggers are demonstrated, exposure to them should be reduced.

House dust mite:

House dust mite control measures for asthma

A systematic review and meta-analysis of currently available chemical and physical methods to reduce exposure to house dust mite allergens did not demonstrate significant clinical improvement in asthma outcomes and was unable to recommend prophylaxis for mite-sensitive asthmatics as sole therapy (Hammarquist C, et al, CDSR) [LEVEL1]. This review has been criticised on its failure to conduct subgroup analysis in those studies that were successful in reducing HDM allergen levels.

Pollens/ animal dander /mould:

While randomised studies of chamber exposure to these triggers have been conducted, randomised controlled trials on avoiding these triggers in sensitised subjects with asthma are currently unavailable.

Cat dander

Use of a HEPA filter and exclusion of the cat from the bedroom did not improve asthma control (Douglass R, CAR) [LEVEL 2].

Allergen immunotherapy:

Allergen immunotherapy for asthma

Allergen specific immunotherapy, when compared to placebo, significantly reduced asthma symptoms and the need for medication, but there was no consistent effect on lung function (Abramson M, et al, CDSR) [LEVEL 1]. It was not possible, in this review, to compare the size of improvement with immunotherapy to that obtained with other therapies for asthma. One randomised trial reported no benefit of immunotherapy when compared to inhaled corticosteroid treatment [LEVEL 2]. 

 

Infection

Viral infections frequently trigger asthma and steps to be taken when they occur should be included as part of the Action Plan.
(The use of action plans is described in Steps 5 & 6.)

Assess the need for influenza vaccine in adults. Influenza vaccine is not routinely indicated for children with asthma.

Influenza vaccination in asthma: efficacy and side-effects

There are currently insufficient data from randomised controlled trials to determine whether influenza vaccination protects against deterioration of asthma [LEVEL 1]. There is evidence from a randomised controlled trial of a brief reduction in peak expiratory flow following influenza vaccination (Cates C, CDSR) [LEVEL 2].

Treat bacterial infection if present. 

Antibiotic use during exacerbations of asthma

Published evidence does not support the routine use of antibiotics for the treatment of asthma exacerbations in either children or adults. Bacterial infection should be managed as required by the clinical circumstances (Coughlan J, CAR) [LEVEL 2].

 

Gastro-oesophageal reflux

There is evidence that micro-aspiration of stomach acid, or reflux of stomach acid over an inflamed lower oesophagus, can lead to bronchospasm in people with asthma. Asthma control may be better in these individuals if reflux is treated.

Reflux and asthma

In subjects with asthma and gastro-oesophageal reflux, not specifically recruited on the basis of reflux associated respiratory symptoms, there was no overall improvement in asthma following treatment for reflux oesophagitis. A subgroup was reported to gain benefit but it appears difficult to predict who will respond. Currently, Level 1 evidence is not available to support the general application of treatment of reflux oesophagitis to control asthma. Future research should evaluate this therapy in people with reflux-induced asthma symptoms (Gibson P, et al, CDSR) [LEVEL 1].

 

Exercise

At least 80% of people with asthma have symptoms triggered by vigorous exercise.

Nedocromil sodium for preventing exercise-induced broncho-constriction

The prophylactic use of nedocromil sodium (NCS) was effective in significantly inhibiting the severity and duration of exercise-induced bronchospasm. This benefit appeared to be greater in people with more severe EIB. Further research on comparing alternative drugs to NCS in exercise-induced bronchospasm is required (Spooner C, et al, CDSR) [LEVEL 1].

The effects of cromoglycate and beta-agonists on exercise-induced asthma have not been evaluated as part of the evidence-based review; however, randomised controlled trials have been conducted to investigate this topic.

 

Food allergy and food additive intolerance

Foods can trigger acute asthma attacks. 

No Level 1 evidence was identified on the effect of avoiding food allergens or additives on asthma.

Drugs, emotion, irritants, occupational sensitisers, temperature changes

No Level 1 evidence was identified investigating the effects of avoiding these triggers on asthma.