The indoor environment plays a major role for sensitization and elicitation of allergic disease. In this thesis major allergens from house dust mite, cats and dogs were quantitated in dust samples from various indoor locations, i.e. homes of children, Day-care centers and schools. Furthermore, various environmental factors that could influence the levels of allergens in dust and their relation to sensitization and asthma were analysed in three climatic regions.
Information about characteristics of indoor environment (e.g. dampness problems, wall-to-wall carpets, pets at home, Jiving habits) was collected through questionnaires. Residential measurements (e.g. Absoluteindoor humidity, Relative humidity, Air exchange rate/h, Particle counts) were done in 60 homes. Dust sampling was done from 15 different locations in homes, Day-care centers and schools. Major mite (Der p I, Der f I), cat (Fel d I) and dog (Can f I) allergens content in dust were determined by enzyme immunoassays. SPT and/or determination of IgE- antibodies were done on infants and asthmatic children. Some common and simple cleaning methods were assessed with regard to their capacity to reduce indoor allergen exposure levels.
As compared to experience from other parts of the world, mite but not pet allergen levels were low, Higher levels of allergens were found during the second half of the year than during the first half of the year. Mite allergen levels were higher in southern, as compared to central and northern Sweden, whereas pet allergen levels were similar over the country.
The pet allergen levels were higher in Day-care centers and schools than in homes. Dampness/humidity, poor ventilation, no basement, presence of carpets, keeping of pets and visits by pet owners all influenced allergen levels.
Reservoirs of allergens varied, although the most common one was upholstered surfaces. However, it would appear reasonable to collect dust from upholstered surfaces both in bedrooms and in living rooms to analyse the levels of allergens at home.
The prevalence of sensitization to mites was more common in the south whereas pet sensitivity dominated in the north. Among asthmatic children, those who were mite sensitized were exposed to higher levels of mite allergens at home than those who were not. This was not true for pet allergens.
Sensitization to mites was not apparent before the age of 5, but occurred in 17% to pets. Five of six children who developed sensitization to pets had been exposed at home to pet allergen levels below the suggested threshold level (8 p/g dust).
Modern vacuum cleaners equipped with filter devices, reduced the levels of mite allergens in dust during a 5 week period, whereas the influence on pet allergens was confounded by indirect contacts with pets. Tannic acid reduced mite and pet allergens for a limited period of time.
In conclusion, the levels of mite allergens are low while those of pet allergens tend to be high in a temperate region. Unlike mite allergens, pet allergens are ubiquitous in the environment and independent of climatic factors. Dampness problems, increased humidity and poor ventilation, presence of carpets and no basement in the home all increase the risk for mite allergen exposure. In addition to these factors, presence of pets and indirect contacts with pets increase the risk for pet allergen exposure. Sensitization to pets is more common in northern and central Sweden, whereas sensitization to mites is more common in southern Sweden. Sensitization to house dust mites did not occur below 5 years of age in this temperate region while sensitization to pets occurred in 17%. Sensitization to pets occurred below the suggested exposure level of 8 p/g dust at home. Day-care centers and schools should also be considered a cause of allergen exposure. Regular use of modern vacuum cleaners or tannic acid may reduce the levels of mite allergen exposure, whereas to reduce pet allergens exposure a multi-system approach, i.e. cleaning combined with reduction in indirect contacts with pets, should be used.
Linköping: Linköpings universitet , 1994. , 89 p.
1994-02-25, Berzeliussalen, Universitetssjukhuset, Linköping, 09:00 (Swedish)
Papers, included in the Ph.D. thesis, are not registered and included in the posts from 1999 and backwards.