Not likely. Severe allergies may cause much nasal congestion/symptoms and thus can reduce your sense of smell. So, typical sniffle from allergies due to dust mite should not cause loss of sense of smell...Check wtih your doc.
Yes. The most common type of allergic reaction to aerosolized particles is respiratory including nasal, sinuses, and bronchial inflammation as in asthma. Chronic nasal congestion will make your mucosa thick and the nerve endings of the roof of the nose that transmit smell to the brain will not have adequate exposure to the air.