House Dust Mite Allergy in Kolkata Metropolis in Response to Change in Lifestyle

House dust allergy is a fairly common problem among sensitive individuals, resulting in various types of allergic manifestations like allergic rhinitis, atopic eczema, bronchial asthma etc. Although the prevalence of allergic diseases is more common in westernized and developed countries, the incidence is increasing at a rapid pace in developing countries like India too. However, data in this regard is still fragmentary except few scattered information in Indian context. In a rough estimate, in India, 250 million people are suffering from one or more allergic manifestations and the country is the home to around 15-20 million asthmatics. To offer the patients with best possible diagnosis and treatment, the detection of offending allergens are of prime importance. At the same time, early detection of individuals who are genetically at risk of developing allergy to readily available indoor allergens is also an essential element to adopt effective avoidance strategies and to design appropriate therapies. House dust is a complex mixture of substances of plant and animal origin and consists of animal and human dander, debris from wool, feathers, hairs, insects, cotton, silk, jute and synthetic fibers, carpets, beddings, furniture and upholstery, fungal spores, bacteria, microorganisms and shedding from other house hold articles and long been known to cause sneezing and wheezing in sensitive subjects. However, the exact nature of the principal allergen in house dust was unknown for quite a long time. It is now well documented that the mites of the genus Dermatophagoides are the most potent allergens in house dust responsible for allergic manifestations. During last more than 30 years, studies on different aspects of house dust mite allergy have been carried out on Kolkata population including entomological, clinical and immunological findings. The study indicates that the house dust sample contains an allergen, secreted and excreted by the house dust mites and inhalation of this allergen along with dust particles initiates allergic manifestations. The genus Dermatophagoides alone constituted 60% of the total acarine fauna, predominated by D. pteronyssinus (47%) followed by D. farinae and interestingly both the mite species coexisted in the same habitat. Seasonal trend indicates mite counts was higher in pre-monsoon and minimum during winter and areabundant in beds than elsewhere in the house and mostly associated with pillows, blankets, mattresses, padded furniture and carpeted floors etc. and preferably feed on human dander. The study indicates that more than 80 % allergic asthma patients residing in Kolkata metropolitan areas are sensitive to dust mites, especially genus Dermatophagoides Spp. as evident from skin prick test and detection of allergen specific IgE antibodies by Immuno Cap system. It is assumed that changes in life style including diet and dietary habits, acquisition of western lifestyle, low standard of indoor environment, increasing air pollution and over all intolerable psychological stress are blamed for such an increased occurrence and frequent recurrences of allergic manifestations in Kolkata metropolitan areas. Increase use of padded furniture, sofa sets, heavy curtains, wall to wall carpeting, blankets without any cover instead of traditional quilt, use of foam mattress instead of conventional cotton mattress and soft toys favour the growth and multiplication of house dust mites, which ultimately increases the chances and duration of exposure to those indoor allergens. In more than 70% cases these may be attributed to the metamorphic change in lifestyle.