Dust mites flourish in humid conditions so keep humidity levels as low as possible. Air conditioning or even electric blankets can help with this.
A regular dusting and vacuum throughout the house will do a lot to lower dust mite numbers. Use a lightly damp cloth when dusting to avoid surface redistribution. If you can, use a vacuum cleaner with a HEPA filter which stops dust from entering back into the air. It’s a good idea to include soft furnishings and textiles every time you vacuum as well.
Bed linens are another place where you will find large populations of dust mites. Washing the bedding in cool temperatures will not get rid of them completely so make sure the water temperature is no less than 140 degrees Fahrenheit. Another option is to place them in the dryer at a high temperature for 10 minutes.
Air purifiers can be a great help in homes with allergy sufferers but it's good to be aware that these will only help with airborne dust mites. Since dust mites are not usually found in the air, though, an air purifier will not remove them completely.