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Background: Several epidemiology studies have found an increase in the major cockroach allergen Bla g 2 with reported pesticide use. Aims of the study: Our aim was to investigate the effect on the excretion of Bla g 1 and Bla g 2 allergens by cockroaches exposed to sub-lethal doses of the pesticides, boric acid and hydramethylnon gel. Methods: German cockroaches in separate colonies were fed either boric acid or hydramethylnon gel at concentrations of 0.2, 0.1 and 0.01% in their water supply over a 2 week period. Ten colonies were exposed to each treatment concentration. Bla g 1 and Bla g 2 in fecal pellets were measured by ELISA. Results: Cockroaches exposed to boric acid excreted fecal pellets with significantly higher concentrations of Bla g 2 (35 400 U/g) than did controls (12 700 U/g) (P = 0.001). Bla g 1 concentrations were not significantly different. There was no difference in either Bla g 1 or Bla g 2 concentrations between cockroaches that ingested hydramethylnon gel and those in the controls colonies. Conclusions: The application of boric acid, a common pesticide, appears to paradoxically increase the production of Bla g 2, a major allergen, by the surviving cockroaches. This may have important implications in avoidance strategies.

The recently published paper in your jour-nal by Gotzsche and Johansen (1) hascaught our attention. We would like to addsome comments.In this newly updated meta-analysis onhouse dust mite control measures forasthma, 44 trials with a total of 3302subjects were included. When comparedwith the last meta-analysis published by thesame authors in 2004 (2), the newly addedstudies were seen to be based on reductionmethods concentrated only on mattressesand bed covers. It has been demonstratedby Frederick in 1997 (3) and more recentlyby Woodcook et al. (4) that house dustmite reduction measures performed only onthe beddings were not able to decrease themite-allergen exposure. Consequently, it isdifficult to state that mite-allergen reduc-tion is not clinically efficient and should notbe recommended as it has been showed thatthese methods are not able to decreasesignificantly the mite-allergen exposure.It is surprising, that the two multifacetedallergen-reduction studies (5, 6) have notbeen taken into consideration for thismeta-analysis as the conclusion of theprevious meta-analysis suggested thatglobal allergen reduction had to be per-formed (2). These two studies, which gath-ered 937 children for the first one (5) and274 for the second one (6), demonstratedthe efficacy of global allergen reduction onallergen exposure and on clinical outcomesin moderate to severe asthma. In the firststudy published by Morgan et al. in 2004(5), the reduction of allergen exposure wasobtained 1 and 2 years after the interven-tion for Dermatophagoides farinae (Der f 1)in the bed and on the bedroom floor andfor Dermatophagoides pteronyssinus (Der p1) and cockroach on the floor. A significantreduction of days with symptoms was alsoobtained when compared with the controlgroup and the reduction of dust mite (Derf 1) and cockroach allergen levels on thebedroom floor was significantly correlatedwith reduced complications of asthma. Inthe second multifaceted study published in2005 by Krieger et al. (6), it was alsodemonstrated that global reduction mea-sures were clinically more efficient thansingle reduction measures.Moreover, these two studies (5, 6)clearly demonstrated the role of indoortechnicians, performing home visits toachieve a global allergen reduction, andconfirmed the results of the French study(7). Brandt et al. (8) underlined also veryrecently the role of indoor techniciansand recommended that public healthprograms should consider the use oftrained field workers such as medicalindoor environment counselors to preventthe progression of allergic asthma andrhinitis.In conclusion, this last meta-analysis byGotzsche and Johansen on house dust mitecontrol measures for asthma clearly dem-onstrated that specific house dust mitecontrol measures for asthma only concen-trated on the bedding were not efficient onallergen exposure and clinical symptoms.So, we think that it is not yet useful toperform every 4 years a new meta-analysisbased on single mite-allergen reductionmeasures for asthma and suggest for thenext meta-analysis to include multi-facetedstudies.F. De Blay, C. Barnig, M. OttDivision of Asthma and Allergy –Department of Chest Diseases UniversityHospital Strasbourg, Strasbourg, France