I saw it on Teletext this morning - untidy and unmade beds are apparently healthier than beds that are made in the morning! Its all about the environment you create for the bed mites - untidy beds are warmer and drier (for some reason) than properly made beds!
Although maybe thats why you're not supposed to fully make your bed, maybe thats why you should leave the sheets folded back for a few hours first.
http://news.bbc.co.uk/1/hi/health/4181629.stm