Airshower, a device that decreases exposure to allergens which in turn causes a reduction in the inflammation of the lungs that triggers asthma related problems within patients. The Airshower expels clean, filtered air gently over sleeping patients around their head, at 0.5 degree below ambient room temperature. The sum effect of this is a zone free of allergens and other particles around the patients head and shoulders. The change in the circulation of all the air within the patient's bedroom is a secondary effect and not of any importance compared to the clean zone. The slight cooling of air as it passes through the Airshower is a very important part of the filtering process. Under normal circumstance warm moist allergen-loaded air is drawn toward the patient's head which contains a high load of dust-mites, but the cooling helps to halt this process by reversing the air flow so that allergen loaded air is pushed away from the head and torso. The current aim for the trial and the Airshower, as a treatment for asthma, is to show that it can reduce the reliance on steroid based medication and enable the patient to have a greater quality of life.