Background: Exposure and sensitization to the major cat allergen, Felis domesticus allergen I (Fel d I), significant causes of allergic respiratory disease. Many patients who are allergic to cats, however, do not own a cat and there is not an obvious source of allergen in their home environment.
Objective: We investigated the levels of Fel d I in dust from homes of 120 subjects with asthma in two climatologically diverse Canadian cities (Vancouver and Winnipeg). Fel d I levels were related to exposure to cats as well as to skin reactivity to cat dander.
Methods: Dust samples from bedroom floors and mattresses were collected in four different seasons and Fel d I content was determined by 2-site monoclonal antibody based-ELISA.
Results: Although only 18 patients (15%) were cat owners, detectable levels of Fel d I were found on at least one occasion in all homes. The geometric mean concentration of Fel d I on floors was 1.15 micrograms/g of dust (range 0.07 to 26.3 micrograms/g) and on mattresses 0.89 micrograms/g (range 0.01 to 17.4 micrograms/g). Seasonal variation of Fel d I levels was only observed in Winnipeg, where Fel d I concentrations were highest in the winter and spring compared with either summer (P < .05) or autumn (P < .005). The highest Fel d I levels were found in homes with a cat (P < .05), however, rather high levels were also found in homes of patients who did not have a cat but visited others with cats. Cat dander was the most frequent sensitizer (60%) in these patients but no correlation was found between the size of the wheal induced by cat dander extract and Fel d I levels in dust samples.
Conclusion: Cat allergen was universally found in homes of asthmatic patients and this may explain the high frequency of cat sensitization among patients with asthma in these two cities. A seasonal variation in cat allergen was observed in Winnipeg with no variation in Vancouver.