This remedy has an interesting story. While it's part of the long history of Traditional Chinese Medicine, at just over 100 years old it's very new in comparison to other practices such as acupuncture and gua sha.
Mr. Qu Huangzhang of Yunnan Province developed the formula in 1902. The formula was eventually donated to the government, and is credited with saving the lives of many Chinese soldiers.
The remedy is said to work on all forms of excessive bleeding--menstrual, ulcers, surgical, etc. Pills or powders can be taken internally. For bleeding wounds you can pour the powder directly into the wound and cover with a bandage.
Like most herbal remedies, this one has multiple uses. It's also said to be a remedy for aching muscles and joints. The aerosol spray helps improve blood circulation thereby relieving pain and reducing swelling. It’s also good for treating bruises and pain from arthritis, backache, and strains.
There are no adverse side effects for this remedy, but it is advised not to take it if you're pregnant or with cold or raw food. These type of foods require more digestion and may slow down the the effect of the remedy.
Letha Hadady, author of Asian Health Secrets, devotes an entire chapter to this remedy in the book. In the video below she talks about the herbs she plans on taking prior to hip surgery. Skip to 3:37 if you want to go directly to the part where she talks about Yunnan Baiyao.