The Journal of Allergy and Clinical Immunology
Volume 125, Issue 3 , Page 765, March 2010

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  • Robert J. Hancox, MD

      Affiliations

    • Department of Preventive and Social Medicine, University of Otago, Dunedin, New Zealand
    • ,
  • Piush J. Mandhane, MD

      Affiliations

    • Department of Pediatrics, University of Alberta, Edmonton, Canada
    • ,
  • Malcolm R. Sears, MB

      Affiliations

    • Department of Medicine, McMaster University, and Firestone Institute for Respiratory Health, St Joseph's Healthcare, Hamilton, Ontario, Canada

published online 08 February 2010.

Article Outline

 

To the Editor:

We thank Dr Brenna1 for his comments on our article.2 We do not know what aspect of cat and dog ownership might reduce the risk of allergy. As we acknowledge in the article, the apparent protective effect could be a result of exposure to allergens, endotoxins, or perhaps some other exposure associated with pet ownership, as Dr Brenna suggests. However, we do not think that a “healthy worker” effect can account for our findings because neither a family history of allergies nor a personal history of atopy influenced pet ownership.2

Quantifying the exposure to animals over the course of a lifetime is problematic. Even direct sampling of allergens and endotoxin in the home will not be representative of all ages in a person's life and will miss exposures outside the home. With the very high rates of pet ownership that we observed in the Dunedin cohort, it is probable that all participants had some contact with these animals. Nevertheless, ownership of a pet is likely to indicate a higher exposure to the animal than casual contact outside the home, and our findings suggest that it is this high level of exposure to both cats and dogs that may confer a protective effect. Misclassification of exposure would be most likely to reduce the strength of the observed associations rather than produce the associations that we observed.

It remains to be seen what aspect of animal exposure may protect against allergy and whether this can be manipulated to reduce the burden of allergies in the population.

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References 

  1. Brenna OV. Cats and dogs: An attractive remedy versus atopy?. J Allergy Clin Immunol. 2010;125:765
  2. Mandhane PJ, Sears MR, Poulton R, Greene JM, Lou WYW, Taylor DR, et al. Cats and dogs and the risk of atopy in childhood and adulthood. J Allergy Clin Immunol. 2009;124:745–750

 The Dunedin Multidisciplinary Health and Development Research Unit is supported by the Health Research Council of New Zealand. P.J.M. was a CIHR Strategic Training Fellow in the Canadian Child Health Clinician Scientist Program. M.R.S. holds the AstraZeneca Chair in Respiratory Epidemiology, McMaster University.

 Disclosure of potential conflict of interest: R. J. Hancox has received research support from the Health Research Council of New Zealand and Waikato Medical Research Foundation and is Medical Director of the Asthma and Respiratory Foundation of New Zealand. The rest of the authors have declared that they have no conflict of interest.

PII: S0091-6749(09)01727-8

doi:10.1016/j.jaci.2009.11.011

Refers to article:

  • Cats and dogs: An attractive remedy versus atopy? , 08 February 2010

    Oreste V. Brenna
    The Journal of Allergy and Clinical Immunology March 2010 (Vol. 125, Issue 3, Page 765)

The Journal of Allergy and Clinical Immunology
Volume 125, Issue 3 , Page 765, March 2010

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