Borax (sodium tetraborate decahydrate, Na2B4O7·10H2O; the calcined form is known as 煅硼砂)
Nature and flavour. Sweet, salty, cool. Lung and Stomach systems.
Borax — a boron salt, and one of the clearest cases in the materia medica of a substance that has moved out of the medicine chest and into the industrial and household cupboard. Classical texts describe it as clearing heat and resolving toxin, and externally as reducing swelling and preserving against putrefaction. It is the traditional ingredient in powders and washes for sore throat, for ulcers of the mouth and tongue, and for red and painful eyes, and it is a familiar component of the 冰硼散 type of mouth powder. Internally it was recorded for clearing hot phlegm and for cough. That internal use is now historical: borax is officially listed in China among the non-food substances that are illegally added to food, it is not permitted as a food additive, and contemporary Chinese medical practice treats it as an external and topical substance. The traditional external indications on this page are recorded as traditional, and are not claims of established benefit.
性味归经。甘、咸，凉。归肺、胃经。
硼砂，一种硼酸盐，也是本草中「从药箱搬进工业与家务柜」最清楚的一例。古籍记载清热解毒，外用消肿防腐。它是咽喉肿痛、口舌生疮、目赤肿痛的散剂与洗剂的传统成分，也是冰硼散一类口腔散剂的常见组成。内服记载用于清热化痰、止咳。内服现已成为历史：硼砂在中国被正式列入食品中可能违法添加的非食用物质名单，不得作为食品添加剂；当代中医实践将其作为外用与局部用药对待。本页所载外用传统用途属于传统记载，并非已证实有效的声明。
最简要的总结是：硼砂不是食品、不是饮品，也不可内服；不存在任何传统依据可以让家庭自行配制。硼化合物的毒理学记载是清楚的 —— 可经破损皮肤与黏膜吸收，进入体内后并非一过即出而是有蓄积；动物实验中已观察到生殖与发育毒性。婴幼儿与儿童是最脆弱的人群：含硼砂制剂用于婴儿口腔或牙龈曾有中毒报告；自制史莱姆与橡皮泥一类配方中用到硼砂，是公认的儿童暴露途径 —— 这一点即使撇开本页内容也值得知道。孕期与哺乳期避免使用。不宜大面积、用于破损皮肤，或用于幼儿的口腔与黏膜。眼部的传统用途虽有记载，但风险实在，不作自用。贮存按家用化学品对待而非按药材：贴标、干燥、置于儿童不可及处。久不愈合的口腔溃疡或咽痛、以及任何眼部不适，应就医诊视，而不是反复敷散。