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[Compendium of Materia Medica]
[Collected Explanations] Li Shizhen states: Qian Nian Ai (Mugwort of Thousand Years) grows in the Taihe Mountain area of Wudang Mountain. The stems are slender, about one chi high. The root resembles Artemisia lavandulaefolia (Pensong). The leaves are over one cun long, without pointed lobes, green on the surface and white underneath. It blooms with yellow flowers in autumn, smaller than wild chrysanthemum, bearing fruits resembling green pearls or cinnabar grains. Leaves are harvested during the three dog days of summer and dried in the sun. The leaves do not resemble Ai Ye (Artemisiae Argyi Folium), but possess an ai-like aroma; they crumble when rubbed, unlike Ai Ye which forms a fluff. Daoist priests use it as a tribute item.
Leaf

[Properties and Flavor] Pungent, slightly bitter, warm, non-toxic.
[Indications] Deficiency-cold in men, various blood-qi pains in women; decoct in water and take orally (Li Shizhen).

(Shennong Bencao Jing, Upper Grade)
[Names] Tao Hongjing says: Although this belongs to the mugwort category, it does not die after winter, but regenerates from old stalks, hence named Yin Chen (Yinchen Herba); the character 'Hao' was added later.
Li Shizhen says: According to Zhang Yi's Guangya and Wu Pu Bencao, it is written as "Yin Chen" (Dust Accumulation), the meaning of which is unknown?
[Collected Explanations] Mingyi Bielu says: Yin Chen grows on Mount Tai and on hillsides and slopes. It is harvested in May and at the Start of Autumn, then dried in the shade.
Tao Hongjing says: It is now found everywhere, resembling Pensong but with tighter, finer leaves. After autumn, the stalks wither, but it survives the winter and sprouts again in spring.
Han Baosheng says: The leaves resemble Qing Hao (Artemisiae Annuae Herba) but are white on the back.
Meng Xi (Da Ming) says: Yin Chen comes from Hezhou and the southern mountain ridges, also known as Shi Yin Chen (Stone Yin Chen).
Su Song says: It is available along nearby roads, but those from Mount Tai are superior. In early spring, seedlings emerge, three to five cun high, resembling Pensong with tight, fine leaves, without flowers or fruits. Stalks and leaves are harvested in May and July and dried in the shade; this is now called Shan Yin Chen (Mountain Yin Chen). In Jiangning Prefecture, there is a type of Yin Chen with large leaves and thick roots, yellowish-white. By summer, there is a Bai Hao (White Mugwort) in Jiazhou that also resembles Qing Hao with white backs; locals all use it as Yin Chen for medicine. Currently, doctors in the south use several types of Shan Yin Chen. Some explanations state: The Shan Yin Chen used in Bianjing and northern regions resembles Ai Hao (Mugwort), with fine, white-backed leaves, an aroma like Ai, bitter taste, turning black when dry. Those used in Jiangnan have stalks and leaves similar to Jia Yin Chen (Domestic Yin Chen) but larger, three to four chi high, extremely fragrant, with a sweet and pungent taste, commonly called Long Nao Bo He (Brain Mint). The one used in Wu region is Shi Xiang Ru (Elsholtzia splendens), with very fine leaves, yellow color, pungent taste, highly aromatic, and warm nature. If mistakenly taken as a splea-relaxing medicine, it becomes Da Yin Chen. Generally, worldly prescriptions use Shan Yin Chen to treat brain pain, induce sweating to relieve shanghan, move stagnant qi in limbs and joints, resolve phlegm and benefit the diaphragm, and treat fatigue most effectively. Detailed examination of canonical materia medica only mentions treating jaundice and promoting urination, which does not match worldly prescriptions. Now, attempting to use Shan Yin Chen from Bianjing as a muscle-releasing and sweating agent yields little effect; however, Shan Yin Chen from Jiangnan is excellent for treating shanghan brain pain. I have recently seen discussions among physicians stating that Jia Yin Chen can also release the muscle layer, descend obstruction, and remove chest irritability. Prescribers rarely use it, but it can be ground and taken as a drink. This is not recorded in Bencao but originates from folk prescriptions. Yin Chen Hao should be a different substance with distinct indications and cannot be conflated with Shan Yin Chen. This view may not be reliable. However, comparing efficacy, the Jiangnan variety is superior; according to classics, it is not from Bencao. Medicinal prescriptions should be further investigated.
Lei Xiao says: When using, select those with eight-angled leaves, dry in shade, remove roots, cut finely, and avoid fire.
Li Shizhen says: Yin Chen was often cultivated as a vegetable in the past, so Shan Yin Chen is used for medicine to distinguish it from Jia Yin Chen. Hong Shunyu's Lao Pu Fu states: "Intoxicated with purple ginger palms, bathed in vinegar with green Yin Chen threads," referring to this. People in Huaiyang still pick wild Yin Chen seedlings on the second day of the second lunar month, mixing them with flour to make Yin Chen cakes. Later generations, relying on transmitted alchemical methods, caused confusion. Currently, Shan Yin Chen sprouts in February, with stalks like Ai. Leaves resemble pale Qing Hao with white backs, finely divided, tight, flat, and neat. Small yellow flowers bloom in September, fruits are as large as Ai seeds; flowers and fruits resemble Tusi Zi (Cuscutae Semen), though some have no flowers or fruits.
Stalks and Leaves

[Properties and Flavor] Bitter, neutral, slightly cold, non-toxic. Lei Xiao states: Shennong, Qibo, and Lei Xiao: Bitter, non-toxic; Huangdi: Pungent, non-toxic.
Zhen Quan says: Bitter, pungent, slightly toxic.
Meng Xi (Da Ming) says: Shi Yin Chen: Bitter, cool, non-toxic. Fu Sha.
Zhang Yuansu says: Bitter, sweet, slightly yang within yin. Enters the Foot-Taiyang Meridian.
[Indications] Wind-dampness, cold-heat pathogenic factors, heat accumulation jaundice. Long-term use lightens the body, benefits qi, promotes longevity, whitens the face, and enhances years. White rabbits eating it become immortal (Shennong Bencao Jing). Treats generalized jaundice, difficult urination, removes head heat, and eliminates hidden masses (Mingyi Bielu). Opens joints, removes stagnant heat, used for shanghan (Tao Hongjing).
Shi Yin Chen: Treats epidemic febrile diseases with mania, headache, vertigo, wind-eye pain, and malarial fever. Treats women's fixed masses and traumatic injuries with exhaustion (Meng Xi).
[Innovations] Tao Hongjing says: The Immortal Classics state: White Hao, if eaten by white rabbits, makes them immortal. But now Yin Chen claims this, which is likely an error.
Kou Zongshi says: Zhang Zhongjing uses it with great efficacy for shanghan with severe heat causing jaundice, where the body and face are completely yellow. A monk, after shanghan, had incomplete sweating leading to residual heat... [text fragment] ...one-tenth, reduced by two-thirds in ten days, and cured in twenty days. The prescription uses Shan Yin Chen and Shan Zhi Zi (Gardeniae Fructus) each 3 fen, Qin Jiao (Gentianae Radix) and Sheng Ma (Cimicifugae Rhizoma) each 4 qian, ground into powder. Take 3 qian each time, decoct in 4 he of water until 2 he remain, strain, and take warm after meals, stopping when effective. This medicine takes Shan Yin Chen as the base, so it is recorded here.
Wang Haogu says: Zhang Zhongjing's Yin Chen Zhi Zi Da Huang Tang treats damp-heat. Zhi Zi Bai Pi Tang treats dry-heat. If seedlings suffer waterlogging, it causes damp-yellow; if drought, dry-yellow. Dampness requires purging, dryness requires moistening. These two medicines treat Yang Jaundice. Han Zhihe and Li Sixun treat Yin Jaundice using Yin Chen Fuzi Tang. Generally, Yin Chen serves as the sovereign herb, assisted by Da Huang (Rhei Radix et Rhizoma) or Fuzi (Aconiti Lateralis Radix Praeparata), depending on cold or heat.
[Attached Prescriptions] Two old, six new.
Yin Chen Geng: Clears severe heat jaundice, shanghan headache, wind-heat malarial fever, promotes urination. Cut Yin Chen finely, decoct as soup and eat. Raw consumption is also suitable (Shiyi Xinjing).
Generalized skin itching with sores and scabies: Wash with concentrated decoction of Yin Chen; heals immediately (Qianjin Fang).
Yu Feng Disease: Hold two handfuls of Yin Chen Hao, boil in 1.5 dou of water until 7 sheng remain. First wash with Sapo Gum decoction, then wash with this decoction, cooling it before reuse. Wash every other day, otherwise it may cause pain (Cui Xinggong's Zuanyao).
Wind disease with spasms and tightness: One jin of Yin Chen Hao, one shi of Sorghum, three jin of Qu (yeast), mix evenly, brew wine according to standard method, and drink (Shengji Zonglu).
Epileptic jaundice like gold, excessive sleepiness and salivation: Equal parts Yin Chen Hao and Baixianpi (Dictamni Cortex), decoct in two zhong of water, take twice daily (San Shi Liu Huang Fang).
Generalized jaundice: One handful of Yin Chen Hao, one piece of fresh ginger, pound into paste, rub daily on chest and limbs.
Male Alcohol Jaundice: Four roots of Yin Chen Hao, seven Zhi Zi, one large river snail (pounded with shell). Pour one large cup of boiling white wine over the juice and drink; a secret formula.
Hot red swollen eyes: Equal parts Shan Yin Chen and Cheqianzi (Plantaginis Semen). Decoct in water to prepare Chacha San (Tea-Powder Dispersion), take several doses (Zhizhi Fang).