The major culprits for dust allergy are mites (Dermatophagoides farinae and D. pteronyssinus) prevalent in house dust. Universally, dust mites are minute co-inhabitants in almost every household and can not be seen with the naked eye. They are found in almost all home furnishing textiles and their favourite places are mattresses, cushions, carpets, upholstery and soft toys. The reactions in hypersensitive people range from itchy and watery eyes, repeated sneezes and running nose, cough and bronchial asthma to childhood eczema. The dust on which they thrive may comprise cotton, wool lint, animal and human dander, crumbs, pollens, molds, etc.
House dust mites principally feed on human scales which are primarily found in mattresses. Bedding, carpets etc. During occupation, the temperature and humidity of the human body provides an ideal microclimate in the mattresses for dust mites. Development from egg through larva, protonymph, tritonymph to adult requires about a month in cultures, under optimum conditions. An adult mite can live up to three months. Their food comprises of protein particles and fungi present in the dust.
Mites may occasionally become airbone during bed-making. It has also been demonstrated that they secrete or release some allergens during bed-making. The allergen may comprise mites, eggs, dead mites and their excrete A gram of dust mite may contain up to 1000 mites.
Most particles of the faeces, whose physical properties are similar to pollen are deposited on the nasal mucosa and carried to the lungs causing localized inflammatory responses because of the high concentration of allergen.
Control of mite population in the domestic environment is the best method of preventing house dust allergy. The degree of cleanliness determines the number of house dust mites and the allergen level. Common control measures include vacuum cleaning, treating the carpets and bed spreads with insecticides, acaricides and fungicides. Reducing the mite population by interfering with the food chain has also been practised. However, a safe, environment friendly and effective formulation based on natural products for the control of house dust mite is not yet commercially available.