In "Distribution and determinants of house dust mite allergen in Europe: The European Community Respiratory Health Survey II," Jan-Paul Zock, PhD, Municipal Institute of Medical Research, Barcelona, Spain, and colleagues looked to determine the distribution of two common house dust mites and what conditions would affect the level of those allergens in each home.
More than 3,500 samples of dust were taken from mattresses found in homes in 22 different study centers throughout Europe and analyzed for the different dust mite allergens. A bed in each home was stripped of linens and an 80cm x 125cm template was placed on the area of the bed where the participant usually slept, and that area was vacuumed to collect the dust samples.
Researchers found that Der 1 and Der 2 dust mite allergens were detectable in 68% and 53% of all samples, respectively, and that large differences in allergen levels occurred between study centers. Important risk factors for high allergen levels included an older mattress, a lower floor level of the bedroom, limited ventilation of bedroom and for one of the dust mites sampled, the level of dampness in the bedroom. Zock and colleagues concluded mite allergen exposure may be reduced by replacing the mattress regularly and increasing ventilation in the bedroom, particularly in winter.
Another study that resulted from the survey showed cat allergens may be present in homes that are cat-free.
Joachim Henrich, PhD, National Research Center for Environmental Health, Institute of Epidemiology, Neuherberg, Germany, and colleagues' study, "Cat allergen level: Its determinants and relationship to specific IgE to cat across European Centers," measured the quantity of cat allergen in mattress dust, and then analyzed the relationship between cat ownership and the level of cat allergen found in the participants' homes. The study can be found in the articles in press area of the JACI Web site, http://www.jacionline.org.
Like the Zock study, dust was vacuumed from the mattresses, with 2,800 mattresses from homes 22 different communities sampled. Current cat owners' homes had substantially higher amounts of allergens than past cat owners and those who had never owned a cat.
While never having a cat in the home led to a lower concentration of cat allergen, it didn't protect against high cat allergen exposure in communities where cat ownership is common. The researchers concluded that people who do not own cats may still be exposed to high levels of cat allergen in the home because cat ownership is common in their community and they bring the allergen home on their clothes. Indoor smoking was also found to lead to higher level of cat allergens, possibly because cat allergens can bind to the smoking-related particulate matter, and consequently, allergen concentrations might be increased in settled dust.