Air purifiers work by filtering the air in your home and trapping any contaminants in the air. Some common contaminants like dust, mold, smoke, pollen and pet dander can irritate allergies and asthma, so getting rid of these contaminants can help to alleviate your symptoms. However, to get rid of the germs, bacteria and viruses in your air that can make you sick, you will need a UV air purifier.