Mite (Der p 1, Der f 1) and cat (Fel d 1) allergens in the homes of babies with a family history of allergy.

Carpet and floor dust samples were collected in four different seasons, from 39 Swedish homes of babies with a family history of allergy. House-dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen contents were determined by mab ELISA, and the levels were related to various environmental factors. Both mite and cat antigens were detected in 94% of the samples and in all homes, but the levels were low (Der p 1, range 15 ng-1944 ng/g fine dust; Der f 1, range 14 ng-264 ng/g of fine dust; Fel d 1, range 16 ng-3120 ng/g fine dust). Mite-allergen levels were significantly higher (P < 0.001) in floor dust than in carpets, and D. pteronyssinus predominated. In contrast, the levels of cat antigen were significantly (P < 0.05) higher in carpets than in floor dust. There was no clear relation between mite-allergen levels and type of house, except that the higher values were found in homes with dampness problems. Cat-allergen levels were higher than total mite-allergen content, and the highest levels were found in homes with a cat (P < 0.05). Rather high concentrations of cat allergen were also found in homes without a cat, which may explain why cat sensitization is so common in Sweden. As the prevalence of house-dust mite sensitivity is increasing in Swedish children, and as the individual patient threshold for eliciting symptoms varies, we suggest that sensitization may possibly occur at a lower exposure level than generally accepted as risk level for sensitization (2 micrograms/g dust).