I originally wrote about the Chinese herbal product Yunnan Baiyao in 2010, concluding at that time that the evidence supporting its use to reduce bleeding was poor and largely anecdotal:
So we have a treatment with uncertain and unregulated ingredients, no demonstrated plausible mechanism of action, a few in vitro and lab animal studies in journals of questionable reliability, a few small human clinical trials in similarly questionable sources, and two very small veterinary trials in equids which found no effect except possibly on a poorly reliable and subjective test of blood clotting.
I reviewed the literature again in 2016, finding a few new studies which did nothing to strengthen the case for this product:
Despite some suggestive in vitro and low-quality studies, the best evidence available so far does not support that Yunnan Baiyao has any benefit for dogs. The fact that it is unregulated, that there is demonstrated inconsistency in the mineral and metal contents of Yunnan Baiyao from different sources, and that the ingredients are still kept secret by the manufacturers, should also give clinicians pause in considering this for their patients.
Though it hasn’t been very long since my recent review, I ran across another study looking for possible effects of Yunnan Baiyao on one aspect of blood clotting, platelet function and the Buccal Mucosal Bleeding Time (BMBT), which involves measuring the time for bleeding to stop after a standardized cut is made in the gums. Like most of the studies in veterinary patients so far, this one found no reason to believe Yunnan Baiyao can stop hemorrhage.
Frederick J, Boysen S, Wagg C, Chalhoub S. The effects of oral administration of Yunnan Baiyao on blood coagulation in beagle dogs as measured by kaolin-activated thromboelastography and buccal mucosal bleeding times. Can J Vet Res. 2017 Jan;81(1):41-45.
In a randomized controlled crossover trial 8 beagle dogs were given either placebo or 1000 mg of YB orally every 12 h for 5 consecutive treatments. Blood was drawn 24 h before treatment and 2 and 24 h after the last treatment, and the BMBT was measured in each sample in duplicate…There were no adverse effects of treatment and no significant differences between the control and treatment BMBTs or [platelet function] parameters at any time point….Thus, at the dose and frequency of administration in this study YB did not appear to have any clinically significant effects on the measured coagulation parameters.
As I always take care to emphasize, no single study is sufficient evidence to definitively answer most medical questions. But despite the anecdotes that seem so persuasive to many owners and veterinarians, the gradual accumulation of evidence is not encouraging. And though no obvious harm has yet been found, the fact remains that the ingredients in this remedy are not standardized or tested for quality of contamination, and since this would certainly be considered unacceptable and illegal for any conventional medicine, it is hard to justify using it when the chances of significant benefits appear to be quite low.