气微寒，味辛、平。苦而辛，辛浓苦轻，阳中阴也。生微寒，熟温。有毒。
入足阳明经、太阴经、少阳经。
《象》云∶治寒痰，及形寒饮冷伤肺而咳。大和胃气，除胃寒，进食。治太阴痰厥头痛
，非此不能除。
《心》云∶能胜脾胃之湿，所以化痰。渴者禁用。
《珍》云∶消胸中痞，去膈上痰。
《本草》云∶主伤寒寒热，心下坚，下气，咽喉肿痛，头眩，胸胀，咳逆肠鸣。止汗。
消心腹、胸膈痰热满结，咳嗽上气，心下急痛坚痞，时气呕逆，消痈肿，堕胎，疗痿黄，悦
泽面目。生，令人吐；熟，令人下。用之汤洗去滑令尽。用生姜等分制用，能消痰涎，开胃
健脾。射干为之使。恶皂荚。畏雄黄、生姜、干姜、秦皮、龟甲。反乌头。
《药性论》云∶半夏使。忌羊血、海藻、饴糖。柴胡为之使。俗用为肺药，非也。止吐
，为足阳明；除痰，为足太阴。小柴胡中虽为止呕，亦助柴胡能止恶寒，是又为足少阳也；
又助黄芩能去热，是又为足阳明也。往来寒热在表里之中，故用此有各半之意。本以治伤寒
之寒热，所以名半夏。经云∶肾主五液，化为五湿，自入为唾，入肝为泣，入心为汗，入脾
为痰，入肺为涕。有涎曰嗽，无涎曰咳，痰者因咳而动脾之湿也。半夏能泄痰之标，不能泄
痰之本，泄本者，泄肾也。咳无形，痰有形，无形则润，有形则燥，所以为流湿润燥也。
气微寒，味辛、平。苦而辛，辛浓苦轻，属于阳中之阴。生品性微寒，熟品性温。有毒。
入足阳明经、足太阴经、足少阳经。
《本草发挥》（李杲著）说：治疗寒痰，以及因受寒和饮用冷食损伤肺脏导致的咳嗽。大能调和胃气，去除胃寒，促进进食。治疗太阴痰厥头痛，不用此药不能消除。
《用药法象》（王好古著）说：能够胜湿脾胃之湿，所以能化痰。口渴者禁用。
《汤液本草》（张元素著）说：消除胸中痞闷，去除膈上痰饮。
《神农本草经》说：主治伤寒引起的寒热往来，心下坚硬，降逆气，咽喉肿痛，头晕目眩，胸腹胀满，咳嗽气逆，肠鸣。止汗。
消除心腹、胸膈间的痰热满结，咳嗽上气，心下急痛及坚硬痞块，时行疫病引起的呕吐逆气，消散痈肿，堕胎，治疗萎黄病，使面目光泽润泽。生半夏令人呕吐；熟半夏令人通便。使用时需用汤水清洗，去掉滑腻感直至干净。用生姜等量炮制使用，能消除痰涎，开胃健脾。射干是它的引经药。厌恶皂荚。畏惧雄黄、生姜、干姜、秦皮、龟甲。与乌头相反。
《药性论》说：半夏为使药。忌食羊血、海藻、饴糖。柴胡是它的引经药。世俗将其作为肺经药物使用，这是错误的。止吐，归属于足阳明经；除痰，归属于足太阴经。在小柴胡汤中虽然用于止呕，但也辅助柴胡消除恶寒，这又归属于足少阳经；又辅助黄芩清除热邪，这又归属于足阳明经。寒热往来处于表里之间，所以使用此药有各半之意。本用于治疗伤寒的寒热症状，所以名为半夏。经文说：肾主管五液，化为五种湿气，进入体内成为唾，进入肝成为泪，进入心成为汗，进入脾成为痰，进入肺成为涕。有涎称为嗽，无涎称为咳，痰是因为咳嗽而动摇了脾的湿气。半夏能泄痰的标症，不能泄痰的本源，泄本源的是泄肾。咳无形，痰有形，无形则滋润，有形则干燥，所以起到流湿润燥的作用。
Bitter, sweet, slightly cold. Non-toxic.
Indications are attached under the Ginseng Radix et Rhizoma entry.
Qi is slightly cold; taste is acrid, neutral. Bitter and acrid, with strong acridity and weak bitterness; it is Yin within Yang. Raw form is slightly cold; processed form is warm. Toxic.
Enters the Foot-Yangming Meridian, Foot-Taiyin Meridian, and Foot-Shaoyang Meridian.
*Bencao Fahui* (Li Gao) states: Treats cold phlegm, and cough caused by lung injury from exposure to cold and consumption of cold drinks. Greatly harmonizes Stomach Qi, removes Cold in the Stomach, and promotes appetite. For Touhou due to Phlegm-Jue of the Taiyin, this herb cannot be omitted.
*Yongfa Xiang* (Wang Haogu) states: It can overcome Dampness in the Spleen and Stomach, thus resolving Phlegm. Contraindicated for those with thirst.
*Tangye Bencao* (Zhang Yuansu) states: Resolves chest fullness and oppression, removes Phlegm above the diaphragm.
*Shennong Bencao Jing* states: Primarily treats alternating chills and fever from Shanghan, hardness below the heart, directs rebellious Qi downward, sore throat, dizziness, chest distension, coughing with counterflow Qi, and borborygmus. Stops sweating.
Resolves heat-phlegm fullness and accumulation in the heart, abdomen, chest, and diaphragm; coughing with counterflow Qi; acute pain and hard masses below the heart; vomiting and regurgitation during epidemic diseases; dissipates carbuncles and swellings; induces abortion; treats sallow complexion; enhances facial luster. Raw form induces vomiting; processed form promotes bowel movement. When used, wash with decoction until all slipperiness is removed. Processed with equal parts of Shengjiang (Rhizoma Zingiberis Recens), it eliminates phlegm-saliva, opens the stomach, and strengthens the Spleen. Shegan (Radix Belamcandae) is its guiding herb. Dislikes Saojiao (Fructus Gleditsiae Sinensis). Fears Xionghuang (Realgar), Shengjiang (Rhizoma Zingiberis Recens), Ganjiang (Rhizoma Zingiberis Officinalis Qinpi (Cortex Fraxini), Guijia (Carapax et Plastrum Testudinis). Incompatible with Wutou (Radix Aconiti Lateralis Preparata).
*Yaoxing Lun* states: Banxia acts as an envoy. Avoid sheep blood, Haizao (Thallus Sargassii), Yitang (Saccharum officinarum juice). Chaihu (Radix Bupleuri) is its guiding herb. Common usage treats it as a Lung herb, which is incorrect. To stop vomiting, it belongs to the Foot-Yangming; to resolve phlegm, it belongs to the Foot-Taiyin. Although used to stop vomiting in Xiaochaihu Tang (Minor Bupleurum Decoction), it also assists Chaihu in stopping aversion to cold, thus relating to the Foot-Shaoyang; it also assists Huangqin (Radix Scutellariae) in clearing heat, thus relating to the Foot-Yangming. Alternating chills and fever occur between the exterior and interior, hence using this herb implies a "half-and-half" intent. Originally named Banxia because it treats the alternating chills and fever of Shanghan. The Classics state: The Kidney governs the five fluids, transforming them into five dampnesses. Entering internally becomes saliva; entering the Liver becomes tears; entering the Heart becomes sweat; entering the Spleen becomes phlegm; entering the Lung becomes nasal discharge. Saliva present is called Sou (phlegm-rheum); saliva absent is called Ke (cough). Phlegm arises when coughing agitates the Spleen's dampness. Banxia can drain the branch manifestation of phlegm but cannot drain its root; draining the root involves draining the Kidney. Cough is formless; phlegm has form. Formless things moisten; formed things dry. Thus, it serves to moisten through flow and dry through transformation.