Pseudolaricis Cortex (Pseudolarix amabilis (Nelson) Rehd. — the root bark or trunk bark of the golden larch; also written 土槿皮)
Nature and flavour. Acrid, warm; classed as toxic. Lung and Spleen systems.
The bark of the golden larch, a deciduous conifer of the mountains of eastern China and one of the few gymnosperms to enter the Chinese materia medica. It entered the record comparatively late and it has essentially one job: killing parasites and relieving itch, applied externally. It is the traditional application for ringworm of the body, athlete's foot, scabies and chronic itchy rashes, and it is best known today as the basis of the compound larch-bark tinctures sold for fungal skin infection. The diterpene acids known as pseudolaric acids are the constituents usually credited with the antifungal activity, and the published work on them is laboratory and animal work — suggestive, not established in controlled human trials. The classical sources record it as for external use only, and that restriction is the most important sentence on this page.
性味归经。辛，温；有毒。归肺、脾经。
金钱松的树皮（或根皮）。金钱松是中国东部山地的落叶针叶树，也是中药里少见的裸子植物来源之一。它入本草较晚，用途基本只有一个：外用杀虫止痒。它是体癣、手足癣、疥疮与慢性瘙痒性皮疹的传统外用药，今天最为人知的身份是复方土荆皮酊一类治疗真菌性皮肤病成药的主药。通常认为起抗真菌作用的是二萜酸类成分（土荆皮酸），相关研究多为实验室与动物工作 —— 有提示性，但尚未被对照人体试验所证实。古籍明确记载只供外用，这条限制是本页最重要的一句。
文献列为有毒，并记载只供外用 —— 不可内服，本页故意不写任何内服的制剂形式。酊剂以酒精为基质，故易燃，涂于破损皮肤会有刺痛；不适用于面部、外生殖器、大面积皮肤与婴幼儿皮肤。反复或大面积使用可致接触性皮炎；经破损皮肤吸收更不应以身试药。孕期与哺乳期避免使用，并须远离儿童：一瓶深色酊剂放在孩子够得到的地方，就是一次误服的伏笔。金钱松是中国特有的孑遗树种，已列入国家重点保护野生植物名录，因此来源不明的树皮既是质量问题，也是植物保护问题。正在扩散的环状皮疹、或已自行用药数周仍不见好的皮疹，须先让人看一眼，而不是继续换药再抹 —— 环状皮疹并不都是真菌感染，即便是，也常不是单靠外用药能解决的。