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The purpose of the presents study was to analyze the levels of indoor allergens in dust from the homes of asthmatic children in three climatic zones of Sweden, and to assess the importance of some conditions, including humidity and ventilation in the homes, that could influence the allergen levels in house dust. From September to December 1989, 390 house-dust samples were collected from 130 homes of children with moderately severe perennial asthma. The patients were selected on the basis of medication scores. All patients were on medication throughout the year.

Carpet and floor dust samples were collected in four different seasons, from 39 Swedish homes of babies with a family history of allergy. Houseadust mite (Der p .1, Derf 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-3 120 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 μg/g dust). [ABSTRACT FROM AUTHOR]

Seasonal variations in IgE antibody synthesis in vitro were studied in cultures of blood mononuclear cells (MNC) from 11 pollen allergic individuals. The IgE levels were significantly higher in two summer seasons than in the winter and spring between them. Net synthesis was confined to the summer in all but one of the patients. All the IgE in the cultures outside the pollen season represented preformed IgE which was present mainly (59%) in the moncyte fraction. Thus, preformed IgE seems to persist in moncytes at times when there is little de novo synthesis of IgE. [ABSTRACT FROM AUTHOR]

In order to screen for mould allergy, extracts of five common atmospheric moulds (Cladosporium, Alternaria, Penicillium, Aspergillus and Mucor) from various manufacturers were investigated in 150 patients (5-60 years old) with clinical symptoms indicating possible mould allergy. The patients were screened by skin prick test (SPT) and radio- allergosorbent test (RAST). SPT seemed to be more sensitive than RAST as a diagnostic screening procedure (80% positive reactions to one or more species compared to 50%). With a partially purified, standardized preparation of Cladosporium herbarum more positive reactions were obtained than with crude extracts without evidence of any unspecific reactions. The difference between commercial and standardized extracts is most probably a result of a variation of both the biological potency of allergenic determinants and the allergenic composition. A considerable number of negative RAST reactions with standard discs were found in patients with positive skin reactions to partially purified Cladosporium, but RAST seemed to be more sensitive than SPT with the other commercial mould extracts. Based on the screening, a very convincing tendency to IgE-reactivity to other moulds was found in patients reacting to Cladosporium, the most common cause of mould allergy. The results confirm the inadequacy of most mould extracts used in diagnostic procedures and strengthen the value of using standardized extracts. [ABSTRACT FROM AUTHOR]