Purpose of the Study
Exposure to environmental allergens can contribute to the clinical expression of atopic illness, and may play a role in the increasing prevalence of asthma. Domestic cat ownership is high in both New Zealand and the United States. Studies have demonstrated significant cat allergen (Fel d 1) content in cat-free homes and public buildings, perhaps in part attributable to allergen transport on clothing. As young children spend prolonged periods at school, the authors sought to determine the level of cat allergen exposure in the classroom environment.
Eight-year-old children from classrooms in 10 primary schools in the Wellington area were enrolled. Eleven school rooms and 202 articles of clothing were examined. Rooms were similar in construction and had independent heating units.
Flooring was sampled by vacuuming at the entrance and the center of each room. Children's outer garments were identified by fabric and vacuumed in a standardized fashion. The dust obtained was assayed for Fel d 1 content by a monoclonal antibody enzyme-linked immunosorbent assay technique.
There was a strong positive correlation (r2= 0.93) between classroom floor Fel d 1 and pupil cat ownership. Classrooms with carpeted floors had markedly higher cat allergen levels, particularly in the center of the rooms. More than half (55%) had a level greater than 8 μg/m2, quoted as high enough to provoke symptoms in allergic individuals. Ownership was the major determinant of clothing Fel d 1, and 63.4% of children came from homes where a cat was regularly indoors. Clothing levels were lower if the cats stayed out of the bedroom, and higher if the home had several cats, or if the garment was made of fleece or wool. Curiously, allergen levels were three times higher on girl's clothing, even controlling for the factors previously mentioned. A correlation between levels of allergen on clothing and on classroom floors was not found.
The authors found a linear correlation between classroom cat allergen content and prevalence of cat ownership among pupils. High levels of Fel d 1 found on clothing suggests allergen transfer from contaminated homes.
The first step in reducing secondary exposure to Fel d 1 is identifying sources and reservoirs of this seemingly ubiquitous allergen. Previous studies have found similar or higher levels in classrooms in other countries. Although a “school cat” was present in two of the schools included, and one did enter a classroom infrequently (“less than once a week”), these schools did not have the highest allergen levels. Ease of cleaning may explain the variation in levels between fabrics. Perhaps the use of frequently washed cotton outfits and minimal amounts of carpeting may reduce classroom levels of Fel d 1. In addition, by uncovering such substantial and obligatory exposure to cat allergen, this study suggests cat immunotherapy merits greater consideration in cat allergic youngsters with persistent allergic disease. By reserving immunotherapy merely for those with obvious contact with cats, we may be omitting many children who may well benefit.