Major cat allergen (Fel d I) levels in the homes of patients with asthma and their relationship to sensitization to cat dander.

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.