If you fix your bed immediately when you wake up in the morning, tight sheets whihc million dust mites living in your mattress that feed on dead skin cells and sweat, and potentially contribute to asthma and allergy. An unmade bed and open, however, exposes bugs to fresh air and light and help to dehydrate and remove them.

Experts recommend bed after eating breakfast and change sheets once a week - pillowcases up to twice a week if you suffer more clearly exposed the problems and airway.

"We know that mites can only survive through ingestion of water from the atmosphere using small glands on the outside of your body," said Dr. Stephen Pretlove of the School of Architecture at the University of Kingston.

"Something as simple as leaving a bed unmade during the day can you remove moisture from the sheets and mattress so the mites will dehydrate and eventually die," he added.