The distribution of cat and dust mite allergens on wall surfaces

This study was undertaken to determine the distribution of cat and dust mite allergens on wall surfaces and to assess the value of wall-wipe samples as a measure of allergen exposure. Paired samples were collected from 31 homes, 20 homes with cats and 11 homes without, by vacuuming 1 m2 of carpet and by wiping 1 square foot of an adjacent wall. Felis domesticus allergen I (Fel d I) was detected in 30 of 31 settled dust samples (range, not detectable to 832,000 mU/gm; median, 10,250 mU/gm) and in 27 of 31 wall-wipe samples (range, not detectable to 113.7 mU per filter; median, 1.2 mU per filter). There was a significant correlation between Fel d I content in settled dust and wall-wipe samples (rs = 0.73; p less than 0.001). To assess the reproducibility of the wall-wipe method, multiple wipe samples were obtained from 20 homes, revealing a mean coefficient of variation of 110%. In contrast to Fel d I, although Dermatophagoides farinae allergen I was detected in 23 of 25 settled dust samples (range, not detectable to 11,888 ng/gm; median, 1178 ng/gm), it was detected in only four of 25 wall-wipe samples. We conclude that cat allergen, but not dust mite allergen, is widely distributed on wall surfaces and that wipe samples provide a simple and effective means of assessing household exposure to cat allergen.