（《纲目》）
【释名】时珍曰∶ ，石殿也，其滓澄殿在下也。亦作淀，俗作靛。南人掘地作坑，以
蓝浸水一宿，入锻石搅至千下，澄去水，则青黑色。亦可干收，用染青碧。其搅起浮沫，掠
出阴干，谓之靛花，即青黛，见下。
【气味】辛、苦，寒，无毒。
【主治】解诸毒，敷热疮，小儿秃疮热肿（藏器）。止血杀虫，治噎膈（时珍）。
【发明】时珍曰∶淀乃蓝与锻石作成，其气味与蓝稍有不同，而其止血、拔毒、杀虫之
功，似胜于蓝。按《广五行记》云∶唐永徽中，绛州一僧，病噎不下食数年，临终命其徒曰∶
吾死后，可开吾胸喉，视有何物苦我如此？及死，其徒依命，开视胸中，得一物，形似鱼而
有两头，遍体悉似肉鳞。安钵中，跳跃不已。戏投诸味，虽不见食，皆化为水。又投诸毒物，
亦皆销化。一僧方作蓝淀，因以少淀投之，即怖惧奔走，须臾化成水。世传淀水能治噎疾，
盖本于此。今方士或以染缸水饮人治噎膈，皆取其杀虫也。
【附方】旧三，新一。
时行热毒，心神烦躁∶用蓝淀一匙。新汲水一盏服。（《圣惠方》）
小儿热丹∶蓝淀，敷之。（《子母秘录方》）
口鼻急疳，数日欲死∶以蓝淀敷之，令遍，日十度，夜四度。（《千金翼》）
误吞水蛭∶青靛调水饮，即泻出。（《普济方》）
(Compendium of Materia Medica)
[Names] Li Shizhen states: Dian (Indigo), meaning sedimentation, refers to the fact that its dregs settle at the bottom after clarification. It is also written as "Dian" or colloquially as "Dian". In southern regions, people dig pits in the ground and soak Isatis root (Isatidis Radix, Lancao) in water overnight. Then, calcined alumen (Alumen, Duanshi) is added, and the mixture is stirred thousands of times. After clarifying and removing the water, a blue-black substance is obtained. It can also be dried for storage and used to dye fabrics green or turquoise. The foam rising during stirring is skimmed off and dried in the shade, called Indigo Flower (Dianhua), which is Qingdai (Indigo Naturalis), see below.
[Properties and Flavors] Acrid, bitter, cold, non-toxic.
[Therapeutic Actions] Resolves various toxins; applied externally to treat heat sores; treats pediatric alopecia areata with heat swelling and heat-induced edema (Chen Zangqi). Stops bleeding, kills parasites, and treats dysphagia/esophageal obstruction (Li Shizhen).
[Elucidation] Li Shizhen says: Dian (Indigo) is made from Isatis root (Isatidis Radix, Lancao) and calcined alumen (Alumen, Duanshi). Its properties and flavors differ slightly from those of raw Isatis root, but its efficacy in stopping bleeding, extracting toxins, and killing parasites seems superior to that of the raw herb. According to Guang Wuxing Ji (Records of the Five Elements): During the Yonghui era of the Tang Dynasty, a monk in Jiangzhou suffered from dysphagia for several years and could not eat. On his deathbed, he instructed his disciple: "After I die, open my chest and throat to see what is causing me such suffering?" Upon his death, the disciple followed instructions and opened the chest, finding an object resembling a fish with two heads, covered entirely in flesh-like scales. Placed in a bowl, it jumped incessantly. When various foods were playfully thrown in, although it did not appear to eat them, they all turned into water. When various toxic substances were thrown in, they also dissolved. At that time, a monk was making indigo paste, so he threw a small amount of indigo into the bowl. The creature immediately became terrified and ran about, eventually turning into water within moments. The world's belief that indigo water can treat dysphagia likely originates from this story. Currently, some practitioners use water from vats used for dyeing to make patients drink for treating esophageal obstruction, relying on its parasiticidal effect.
[Attached Prescriptions] Three old prescriptions, one new prescription.
Seasonal heat toxin causing mental restlessness and irritability: Take one spoonful of Blue Indigo (Lan Dian) mixed with one cup of freshly drawn water. (Taiping Shenghui Fang)
Pediatric erysipelas (heat dan): Apply Blue Indigo (Lan Dian) externally. (Zimu Milu Fang)
Acute gangrene of the mouth and nose, fatal within days: Apply Blue Indigo (Lan Dian) externally to cover the area thoroughly, ten times daily and four times nightly. (Qianjin Yi Fang)
Accidental ingestion of leeches: Drink Green Indigo (Qing Dian) mixed with water; the leech will be expelled through defecation. (Puji Fang)