Nose breathing ensures that inspired air is warm, filtered and moist and may therefore benefit patients with asthma. It features in some complementary approaches to treat asthma and is encouraged at night in the Buteyko technique by the use of mouth taping. In this pragmatic study we sought to determine whether taping the mouth at night has any effect on asthma control compared with usual breathing in patients with symptomatic asthma, since if it was effective it would be a simple intervention to implement.

This was a randomised, single-blind, crossover study of participants (n=51) with symptomatic asthma (mean FEV₁ 86% predicted). A 4-week period of usual breathing at night was followed by use of mouth taping with microporous tape, as in the Buteyko technique, or vice versa, with a 2-week run-in period and a minimum 2-week washout period of usual breathing between ‘treatments’. Primary outcomes were morning peak expiratory flow and symptom scores (Asthma Control Diary). Outcomes were measured and analysed without knowledge of treatment allocation.

Fifty participants completed the study and reported taping their mouth for a median 26 of 28 nights. Although 36 participants said mouth taping was very or fairly acceptable there were no differences between treatments for morning peak expiratory flow (mean difference −1l/min (95%CI, −9 to 7)) or symptoms scores (mean difference −0.12 (95%CI, −0.30 to 0.06)) nor for any secondary measures.

Taping the mouth at night had no effect on asthma control in patients with symptomatic asthma. (Registered: ISRCTN74428617). Trial Registration Number: ISRCTN74428617.