Acupuncture causes the contracted muscular walls to dilate; the mechanism of this is unknown, but there is good Western research data to support this claim. A recent Chinese clinical trial on asthma showed that some 70 per cent of asthmatics gained a 'good effect' from a course of acupuncture and moxibustion (about ten treatments) once a year. The acupuncture treatment was able to decrease the frequency and intensity of asthmatic attacks over a period of a year. This result is encouraging as it shows that acupuncture and moxibustion can affect the response of the body to the environmental stimuli causing asthmatic attacks.