Allergic Rhinitis and its Impact on Asthma - ARIA

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ALLERGIC RHINITIS AND ITS IMPACT ON ASTHMA GUIDELINES ● 2010 – V. 9/8/2010 There were no direct adverse effects of these prophylactic interventions but there is inconvenience, cost of using multiple preventive measures, <strong>and</strong> psychological burden on parents who cannot afford them. Conclusions <strong>and</strong> research needs Net clinical benefit from reducing exposure to house dust mite allergens in early childhood is uncertain. In children at high risk multifaceted interventions may reduce the risk of developing asthma, but it is unclear which aspects of the interventions would be most effective. The effect on development of allergic rhinitis is less certain <strong>and</strong> the effect on atopic dermatitis is unlikely. There is no evidence concerning children at average risk of developing allergy, but if present the effect would probably be even smaller in this population. Recommendation In infants <strong>and</strong> preschool children, we suggest multifaceted interventions to reduce early life exposure to house dust mite (conditional recommendation | low quality evidence). Underlying values <strong>and</strong> preferences: This recommendation places a relatively low value on the burden <strong>and</strong> cost of using multiple preventive measures (e.g. encasings to parental <strong>and</strong> child’s bed, washing bedding <strong>and</strong> soft toys at temperature exceeding 55°C [131°F], use of acaricide, smooth flooring without carpets, etc.), <strong>and</strong> relatively high value on an uncertain small reduction of the risk of developing wheeze or asthma. For some children at lower risk of developing asthma <strong>and</strong> in certain circumstances an alternative choice will be equally reasonable. Remarks: Children at high risk of developing asthma are those with at least one parent or sibling with asthma or other allergic disease. Question 5 Should infants <strong>and</strong> preschool children avoid exposure to pets at home to reduce the risk of developing allergy <strong>and</strong> asthma? Summary of findings Two systematic reviews of observational studies reported that early life exposure to pet allergens may increase the risk of asthma in children (102, 103), although the estimated effect was small <strong>and</strong> inconsistent including some studies that showed a reduced risk. Authors of the review suggested that this heterogeneity might have been caused by inappropriate time sequence of the exposure <strong>and</strong> outcome <strong>and</strong> a potential selection bias in individual studies. In studies ensuring the appropriate temporal sequence, previous exposure to pet allergens was not associated with increased risk of asthma (odds ratio: 0.99, 95% CI: 0.77 to 1.27) or wheezing (odds ratio: 0.80, 95% CI: 0.59 to 1.08) in children ≤6 years of age. In older children (>6 years) the risk might be higher both for asthma (odds ratio: 1.15, 95% CI: 0.86 to 1.56) or wheezing (odds ratio: 1.30, 95% CI: 1.11 to 1.52). We did not identify any systematic review addressing the question if avoidance of pet allergens prevents the development of allergy or asthma. We also did not identify any r<strong>and</strong>omised trial evaluating avoidance of pet allergens as a single intervention to prevent the development of allergy or asthma. PAGE 34 OF 153
ALLERGIC RHINITIS AND ITS IMPACT ON ASTHMA GUIDELINES ● 2010 – V. 9/8/2010 However, three r<strong>and</strong>omised trials of birth cohorts evaluated the effect of multifaceted interventions on the development of allergy <strong>and</strong>/or asthma – the Canadian Childhood Asthma Primary Prevention Study (86-88), the Prevention of Asthma in Children study (89), <strong>and</strong> the Study on the Prevention of Allergy in Children in Europe (90, 91). We used data from these trials to estimate the overall effect in a meta-analysis <strong>and</strong> used them to prepare the evidence profile. In these three trials families of children considered to be at high risk of developing allergy <strong>and</strong>/or asthma (at least one first degree relative with asthma or other allergic disorder) were r<strong>and</strong>omly assigned to multifaceted interventions (frequent ventilation of the child’s room, encasings to parental <strong>and</strong> child’s bed, washing bedding <strong>and</strong> soft toys at >55ºC, use of acaricide, smooth flooring without carpets, various dietary interventions, <strong>and</strong> were advised to part with a pet or keep it outside). Compliance with the recommendation to part with a pet or keep it outside was variable; in one study 51% families complied with the recommendation (104), <strong>and</strong> in the other 17 families (34% of 50 families that had a cat at baseline) parted with the cat, but 6 families acquired a new cat over a period of 2 years (105). Benef<strong>its</strong> After 2 years of observation there was no significant difference between the multifaceted intervention <strong>and</strong> control groups in the percentage of children who developed rhinitis, recurrent wheezing, or atopic dermatitis (eczema), but results were not precise enough to exclude important benefit or important harm from the intervention. Multifaceted intervention seemed to reduce the risk of asthma after 2 years of follow-up, but the results were imprecise, including no effect. Only one study (86) reported results after more than 2 years of follow-up. There was a similar risk of development of allergic rhinitis <strong>and</strong> atopic dermatitis (eczema) after 7 years, although the results were imprecise. However, multifaceted intervention was associated with lower risk of developing asthma after 7 years (relative risk: 0.44, 95% CI: 0.25 to 0.79). Harms There were no direct adverse effects of these prophylactic interventions except for inconvenience <strong>and</strong> cost of using multiple preventive measures. Conclusions <strong>and</strong> research needs All available evidence for the benefit from avoiding pet allergens in childhood comes from interventions in high-risk families, <strong>and</strong> is very indirect <strong>and</strong> imprecise. Any clinical benefit from avoiding exposure to pet allergens in childhood is therefore very uncertain, <strong>and</strong> there is even some uncertainty if there is a risk associated with the exposure. Further well designed <strong>and</strong> rigorously executed r<strong>and</strong>omised trials of pet allergen avoidance that measure <strong>and</strong> properly report (74, 75) patient-important outcomes are needed. Recommendation In infants <strong>and</strong> preschool children, we suggest no special avoidance of exposure to pets at home (conditional recommendation | low quality evidence). Underlying values <strong>and</strong> preferences: This recommendation places a relatively high value on possible psychosocial downsides of not having a pet, <strong>and</strong> relatively low value on potential reduction in the uncertain risk of developing allergy <strong>and</strong>/or asthma. Remarks: Clinicians <strong>and</strong> patients may reasonably choose an alternative action, considering circumstances that include other sensitized family members. PAGE 35 OF 153
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