Black Catechu Classic Formulas — Natural Herb Library

Primary Actions

Stops bleeding and promotes tissue repair - used for bleeding trauma, ulcerated sores, and lesions that need both rapid hemostasis and restoration of damaged tissue.
Astringes sores and dries damp exudation - applied externally for weeping eczema, chronic ulcers, oral ulceration, and damp erosive lesions that are slow to close.
Moves Blood locally and relieves traumatic swelling - a common role in powders and trauma preparations where bruising, seepage, and pain occur together.
Can be used internally in small doses for heat irritation in the mouth and throat - a secondary use that relies on its cool astringent character rather than bulk detoxifying action.

Qi Li San (七厘散) - classic trauma powder using catechu to assist bleeding control and tissue healing while companion herbs move Blood and reduce pain.
Long Gu Er Cha San (龙骨儿茶散) - external powder tradition for damp weeping eczema and ulcerative lesions where catechu helps dry, astringe, and regenerate tissue.

TCM Wiki lists Hai Er Cha, Hei Er Cha, and Er Cha as overlapping names for black catechu and assigns the same traditional actions of stopping bleeding, promoting regeneration, and treating trauma.
Me and Qi notes that pharmacopoeial black catechu is sourced from Acacia catechu and cautions that similar trade blocks are not always identical in origin.
IMPORT NOTE: This `-2` file is a synonym record rather than a distinct herb, retained because the spreadsheet imported the alternate pinyin Hai Er Cha.