Picture: Amber, one of the main ingredients of Nei Yi Wan No picture? Click here.
Nei Yi Wan has just three ingredients, according to ITM: turtle shell (鳖甲 Bie Jia or 龟板 Gui Ban), vinegar-treated rhubarb (醋炒大黄 Cu Chao Da Huang), and succinum (琥珀 Hu Po). From Reuters:
"I think the positive message is that Chinese herbal medicine may offer equivalent benefits to conventional medicine but with fewer side effects," lead researcher Andrew Flower, of the University of Southampton in the UK, told Reuters Health.
Here's a link to the original study, from the Cochrane Library: Chinese herbal medicine for endometriosis
Finally and most interesting to people in the TCM world, an exhaustive article by Subhuti Dharmananda of the Institute of Traditional Medicine, detailing the many different Chinese herbal approaches to endometriosis: Chinese Herbal Therapy for Endometriosis.