• allergen avoidance;
  • encasing;
  • house-dust mites;
  • indoor humidity;
  • mite sensitization

Wickman M, Nordvall SL, Pershagen G, Korsgaard J, Johansen N, Sundell J. Mite allergens during 18 months of intervention.

In Stockholm, Sweden, 17 children with newly diagnosed sensitization to house-dust mites (HDM) and 11 children with previously diagnosed HDM-sensitization were included in a study of HDM-allergen avoidance. Mattress dust was collected on repeated occasions during 18 months and assayed for concentration of major HDM allergens. During the first 12 months, the parents of the intervention group were instructed to intensify cleaning and airing of the child's bedroom. During the last 6 months of the study, the mattresses and pillows of seven children in the intervention group and sibling controls were encased in semipermeable polyurethane covers. The homes exhibited a high absolute indoor humidity throughout the year, and even during the winter the mean levels exceeded 7 g/kg. No mite allergen reduction was seen in the intervention group during the first year. However, among the newly diagnosed HDM-sensitized children, there was a mean reduction of the mattress mite allergen concentration of 83% (P= 0.02), and this was most pronounced in the homes with low humidity. At the end of the mattress encasement period, an average difference of 98% (P< 0.001) was found between the vacuumed amount of mite allergen on top of the covers and that underneath.