Stringent environmental control in pregnancy and early life: the long-term effects on mite, cat and dog allergen A.Simpson,B.Simpson,A.Custovic,M.CravenandA.Woodcock North West Lung Research Centre, Wythenshawe Hospital, Manchester, UK Summary Background As part of a primary prevention of asthma study, we measured the effect of environ- mentalcontrolmeasuresonDerp1,Feld1andCanf1overa3.5-yearperiod. Methods High-risk infants (both parents atopic) without pets, were randomized to the Active group (n  142, vinyl flooring in child's room, allergen-impermeable cot mattress, hot-washable toy, mite allergen-impermeable encasings to parental bed and to child's bed when older, high filtrationvacuumcleaner,hot-washingofbedding)ortheControlgroup(n  136,nointervention), inearlypregnancy.Dustsamplesfromtheparentalmattress,livingroomfloor,child'smattressand flooratbaseline(pregnancy),birthandat3yearswereanalysedforDerp1,Feld1andCanf1. Results A total of 278 families completed the baseline visit, 259 the birth visit and 239 the 3-year visit.IntheActivegroupat3years,58%remainedcompliantwithallmeasureslikelytoreducethe child's exposure to allergen and 77% of parents still used encasings on their bed. Levels of Der p 1, Fel d 1 and Can f 1 were significantly lower in the Active group in the child's floor and the child's mattressat3yearscomparedtotheControlgroup(P < 0.001).Fortheparentalmattress,thelevels of Der p 1 and Fel d 1 were lower in the Active group (P < 0.001) and there was a strong trend towardsalowerlevelforCanf1.Therewasnodifferenceinthelevelsofanyoftheallergensbetween thegroupsinthelivingroomfloor.Childrens'bedroomswithnodetectablemite,catordogallergen weresignificantlymorecommonintheActivethantheControlgroup(25vs.2, P < 0.001). Conclusions Environmental control measures are effective in substantially reducing levels of Der p1,Feld1andCanf1inhomeswithoutpetsinthelongtermandareacceptabletofamilies.The effect of this environmental manipulation on the development of sensitization and allergic disease remainstobeseen. Keywords Canf1,Derp1,environmentalcontrol,Feld1,primarypreventionofasthma Submitted 18 November 2002; revised 13 February 2003; accepted 28 February 2003 Introduction Many patients with asthma are allergic to house dust mites. Studies of mite allergen avoidance in adults with asthma have oftenusedmeasureswhichwereineffectiveinreducingallergen exposure[1]orhavebeenoftooshortdurationtoseeachange in lung function [2, and reviewed in 3]. The Cochrane Review concludedthatallergenavoidanceshouldnotberecommended inthemanagementofasthmainadults[4].However,studiesin children have produced more promising results [5], and atten- tionhasnowturnedtotheinvestigationoftheseenvironmental control methods in the primary prevention of asthma in high- risk infants. As part of the National Asthma Campaign Manchester Asthma and Allergy Study ( NAC MAAS), we have designed and installed bedrooms for high-risk infants/young children, using stringent environmental control measures developed originally to reduce mite allergen exposure. We have shown previously that such rooms are acceptable to parents and, when used in conjunction with mattress and bedding encasings in the parental bedroom, can signi®cantly reduce exposure to miteallergeninthe®rstyearoflife[6]. Sensitizationtocatsanddogsisariskfactorforasthma.The relationshipbetweenpetownership,petallergenandthedevel- opment of sensitization to pets is confusing, and a wealth of recentpublicationshasfailedtoclarifytheissues.Aprospective birth cohort study has, however, identi®ed increasing exposure toFeld1asariskfactorforsensitizationtocatbyage7years [7]. Many children who are sensitized to cats and dogs have neverlivedwiththesepets[8].LevelsofFeld1andCanf1tend to be higher in homes with pets, but pet allergen is not only foundinmosthomeswithoutpets[9,10]butcanbedetectedon trains, planes and automobiles [11,12], in the air of hospital outpatient clinics [13] and in nursery schools [14], i.e., places where pets have never been. A primary prevention of asthma study from Canada has reported that Fel d 1 levels can be reduced in the parental bed after intervention with encasings for up to 2years, but found no effect on infant beds [15]. A similar effect on Fel d 1 was seen in an allergen avoidance Correspondence: A. Simpson, North-west Lung Research Centre, Wythenshawe Hospital, Manchester M23 9LT, UK. E-mail: asimpson@fs1.with.man.ac.uk Clin Exp Allergy 2003; 33:1183±1189 ß 2003 Blackwell Publishing Ltd 1183