Hello, moxibustion is one of the external methods of traditional Chinese medicine, which has a good effect of invigorating qi and strengthening yang. The back belongs to the yang side in the human body, and back moxibustion has a good aphrodisiac effect. It's 5-7 o'clock in the evening, the sun has set, and the yang of the human body must enter the yin blood before people can fall asleep normally. If moxibustion is carried out at night, it may lead to yang failing to enter yin, leading to insomnia. But not everyone will suffer from insomnia when doing moxibustion at night, which varies from person to person. Some people with poor yang will sleep well if they do moxibustion at night. I hope it helps you!