Sorry, asthmatics. If dust mites and their allergens trigger your symptoms, efforts to obliterate them probably aren't working. Many people attack the problem with chemical agents, high-tech vacuums, ionizers and air-filtration gadgets, and mattress and pillow encasings, as well as by washing linens in hot water—but all are actually useless desperate measures, according to a new review of the literature. The meta-analysis involved scrutiny of 54 studies of 3,000 people with asthma and appears in The Cochrane Library this month. Most homes are loaded with mites and allergens; even if their numbers are reduced, what remains is sufficient to induce asthma attacks, the researchers conclude. "I realize that our findings are unwelcome," says lead author Peter Gotzsche, director of the Nordic Cochrane Centre in Denmark, "but those are the facts." To stave off symptoms, in other words, relying on your medication will have to do.