Variability of cat-allergen shedding.

To study the differences in total allergen shed, nine cats were placed individually in a lucite chamber with an air sampler attached for 1 hour. With a RAST-inhibition assay that used specific cat IgE antibodies from cat-sensitive subjects, we ranked the allergen production of each cat. From these nine cats, three high producers and one low producer were studied further. Each cat's allergens were collected for two to four separate 1-hour intervals on 6 different days. The high producers' samples remained high in allergen content, and the low producer's sample remained low. An additional eight cats were selected for similar longitudinal measurements, and allergens from each of these 12 cats were collected during four 1-hour intervals on 2 different days and assayed for total allergy units (AUs) by RAST inhibition and for the major cat allergen, Fel d I, by a two-site assay with a monoclonal antibody. Shedding, particularly by high producers, varied considerably from hour to hour. We found a hundredfold difference in AUs between the mean rate of shedding of the highest and lowest producers and a sixfold difference in Fel d I units. Variation in rate of shedding of Fel d I accounted for about half the variation of shedding of AUs. Allergen shedding varies not only between cats but also in the same cat during the course of a day and between days. Male cats shed more than female cats.