Africa.

A patient comes to you asking whether using a mat-tress cover would help her allergic rhinitis. You know that she is allergic to house-dust mites and you know also that bedding covers have been widely recom-mended for allergic rhinitis, not least by several clinical guidelines.1,2 You have also heard however that some doubt has been cast on the evidence supporting these recommendations. With your interest raised, you deter-mine to try to find out for yourself... So what is the question? To get the right answer one first needs the right ques-tion. One question might be: ‘In people with allergic rhinitis, what is the effect of impermeable bedding cov-ers on the symptoms of allergic rhinitis?’ The type of evidence to look for, an