Hello Varun, Sorry to note your sister s symptoms. Dust allergy has become a major problem with the growing urbanisation, changes in housing with little natural light or air and reliance on A/C units that increases the humidity. Allergy testing is highly recommended to know the extent of her allergies, whether it is house dust mite, or mixed with animal dander, moulds, fungal spores, grass pollens etc. There are various private labs in Mumbai that offer blood test (would recommend specific IgE test rather than others) such as Metropolis etc and these need to be reviewed by an experienced Chest physician with interest in Allergy or an Allergist. Long acting antihistamines such as allegra 180 oce daily, nasonex nasal spray 2 sprays/nostril for 3 months is recommended. The tests will guide duration and seasonal therapy. I hope this helps. Best Wishes.