The information provided here is not a replacement for a doctor. You shouldn't use it for the purpose of self-diagnosing or self-medicating but rather so you can have a more informed discussion with a professional TCM practitioner.
Because it is a herb specifically indicated to treat painful obstruction syndrome as can be seen on Erythrinae Bark's page.
Erythrinae Barks is a Neutral herb that tastes Bitter and Pungent. It targets the Spleen, the Kidney and the Liver.
Its main actions are: Treats Painful Obstruction Syndrome due to Wind-Damp, removes Stagnation and unblocks Channels. Promotes urination and reduces edema. Relieves itching skin lesions and kills parasites. Treats toothache due to dental caries.
Dental caries Lower back pain Knee pain Extremities spasms Edema Scabies Skin lesions