Buying a new mattress can be a temporary solution but one study has shown that house dust mites colonise a new mattress within just four months. A longer term solution is to fit a special cover that is designed so that house dust mites and allergens cannot escape from the mattress into the bedding. The best types are those which cover the entire mattress rather than just the top. Most of the big department stores stock these covers and others are advertised in the press. There is no evidence that shows that particular brands are better than others.
Most leading brands are likely to be effective at controlling house dust mites.
You will also need to wipe down the covers frequently to prevent a build up of dust on their surface. Most baby mattresses are now covered and these would be suitable to minimise the levels of dust mite and allergens. As is the case with any chemical there is a chance that these chemicals may provoke allergic reactions in some people. Until more independent research becomes available, the National Asthma Campaign is not in a position to make recommendations on these types of cover. There is some debate as to which is best to buy - feather or synthetic.