Mites and house dust allergy.

Abstract

"Is a Mite (Dermatophagoides sp.) the Producer of the House Dust Allergen?" was the title of the first paper by R. Voorhorst and co-workers' in 1964. Their findings are now largely confirmed that all but a small proportion of patients sensitive to house dust are allergic to extracts of the universally distributed acarine mite genus Dermatophagoides.2-8 The most important European species, D. pteronyssinus, is 0 3 mm in length and grows well on human skin scales. Many thousands can be cultured on 250 mg according to F. T. M. Spieksma.' It is said that on average a person sheds 5 g of dander per week,'0 thus ensuring no lack of culture medium for mites in the house and more especially in the bed. The Dutch workers1' with painstaking thoroughness found the mites in the house dust of all the homes examined in Holland, and particularly in damp homes. Of the total number of mites found, the Dermatophagoides spp. made up 70%, and D. pteronyssinus comprised 80% of these. This mite grows best at about 25°C (86 F) and at a relative humidity of 80% with a seasonal spurt in growth from September to November, when the Dutch patients with house dust allergy are most affected. Another species, D. farinae, Wvhich grows more readily on cereal media such as dogmeal, seems to be the more important in Egypt and the U.S.A.'"13 In Japan, where D. farinae was first identified as a source of house dust allergen,2 it is now thought from an examina tion of all the different mite genera and species found in the house dust that the total mite content accounted for the allergenicity of the dust from different parts," even though D. pteronyssinus was still present in the largest numbers. Few or no Dermatophagoides spp. have been found in house dust collected at high altitudes in cold climates, such as Davos, where heating in the home keeps the humidity low.'3 Dermatophagoides spp. of mites and their particles are present in the air during bed-making at home, though not in hospitals,'6 as is evident from the usual history given by patients with rhinitis and asthma due to house dust allergy. The mites have been isolated from the dust by mechanical sieving and flotation with dichloromethane or lactic acid. More recently" ultrasonic treatment of house dust in a detergent solution has been found to dislodge the mites from the fibrous and other debris. The addition of crystal violet to the centrifuged deposit stains the solid material, but not the