Vacuum the couch -- including the arms, back, sides and cushions -- with a vacuum cleaner that has a HEPA filter. Vacuum at least once or twice a week to keep dust mites and dander under control. If the cushions are removable, vacuum both sides.
Remove pet hair -- which attracts dust mites -- from the sofa daily if pets climb onto it. Use a roller specially designed to remove pet hair, or a lint roller. Afterward, wipe down the sofa with a wet cloth to remove some of the dust mites as well.
Remove the throw pillows. Alternatively, vacuum them every week. If possible, also wash them once a month in the washer on the hottest water setting. Dust mites die if washed in water at 130 degrees Fahrenheit or hotter.
Run a dehumidifier to help keep the dust mite population down. They thrive in a humid environment. Adopt a few other habits as well, such as vacuuming the floor weekly, dusting with an electrostatic duster that traps dust and brushing your pets every day.