Sulfur (the mineral, purified)
Nature and flavour. Sour, warm; classed as toxic. Kidney and Large Intestine systems.
Elemental sulfur — one of the few substances in the materia medica that is neither a plant nor a mineral salt. It does two different jobs. Externally, classical texts describe it as counteracting toxin, killing parasites and relieving itch, and it is the traditional external application for scabies, ringworm, obstinate sores and chronically weeping skin complaints; sulfur also remains a recognised topical agent in modern dermatology, which is unusual among these entries. Internally, the classical texts describe it as supplementing the fire of the gate of life and warming the Kidney, and record it for cold-type constipation and for the impotence and cold weak back that traditional medicine attributes to decline of that fire. That internal use rests entirely on the traditional record, and in practice it depends on the processed form. The gap between the two jobs is the point: a substance that is mild on the skin is not mild taken by mouth.
性味归经。酸，温；有毒。归肾、大肠经。
一味单质硫，是本草中少见的既非植物也非矿物盐类的药。它承担两类不同工作。外用方面，古籍记载解毒杀虫止痒，为疥疮、癣疮、顽疮与慢性渗液性皮肤病的外用常药；硫在现代皮肤病学中至今仍是公认的外用成分，这一点在本类药中并不常见。内服方面，古籍称其补火助阳、温肾，用于虚寒便秘以及传统归为命门火衰的阳痿与腰膝冷弱。内服用途完全属于传统记载，且实际使用依赖炮制品。两类工作之间的落差正是要点：外用温和的物质，内服并不温和。
文献列为有毒。单质硫对完整皮肤的急性毒性不高，但硫并非无害：反复或大面积使用会使皮肤干燥受刺激，可致接触性皮炎，包扎覆盖或强烈日晒后更明显。绝不可近火或加热 —— 硫燃烧产生二氧化硫，是密闭空间内有危险的刺激性气体。古籍所载内服不属于自用实践，最大的理由不在硫本身而在于伴生杂质：天然矿物硫多次被检出砷污染，传统的应对办法是炮制，而炮制是生产环节，不是家庭能完成的。孕期与哺乳期及儿童同样因此避免使用。任何正在扩散、渗液或久不愈合的皮肤问题都须先明确诊断。疥疮尤其具有传染性且属于需要诊断的疾病：要考虑全屋接触者，而不是一个人自行抹硫。
1 related entry.