Some polyfoam pillow makers boast that memory foam is less prone to dust mites than down or feathers. This isn’t true. The best way to minimize dust mite allergen exposure is to cover pillows and your mattress with allergy-proof encasements and to wash other bedding regularly (once a week). Regular vacuuming with a HEPA filter vacuum and the use of a HEPA air filter in the bedroom can also help, as can keeping household humidity levels low.