General Principle: In spring, emesis (催吐) is appropriate. When using emetic decoctions, stop as soon as the pathogenic factor is expelled; it is not necessary to consume the entire dose.

If the symptoms resemble those of Guizhi Tang Syndrome (Cinnamon Twig Decoction Syndrome, a syndrome of exterior deficiency with sweating), but there is no headache or stiffness in the neck, and the cun pulse is slightly floating, with a sensation of fullness and hardness in the chest, qi rushing up to strike the throat causing difficulty in breathing, this indicates cold retained in the interior and emesis should be induced. (Another view states that this is due to long-standing phlegm-rheum in the interior, making emesis appropriate.)

If there are various excess conditions (or cold conditions) in the chest, with a feeling of oppression and pain in the chest, inability to eat, and pressing on the chest induces salivation and sputum, accompanied by diarrhea occurring more than ten times a day, with a pulse that is surprisingly slow and the cun-kou pulse slightly slippery, emesis may be used. After emesis, the diarrhea will cease.

In Shaoyin Disease (disease affecting the Shaoyin channel), if food is vomited immediately upon entering the mouth, and there is a sensation of distress in the heart with an urge to vomit but inability to do so, emesis is appropriate.

Furthermore, if leftover food stagnates in the upper jiao (upper stomach), with cold extremities, and a pulse that suddenly becomes knotted, because pathogenic qi is lodged in the chest, causing fullness below the heart and irritability with an desire to eat but inability to swallow, where the disease is located in the chest, emesis should be induced.

Wu [referring to a specific physician's experience]: For diseases located above the diaphragm, with a large pulse, chest fullness, and abundant phlegm; or for food stagnating at the stomach opening with a slippery pulse, emesis is appropriate. Hua Tuo stated that for Shanghan (Cold Damage) occurring three to four days after onset, when the pathogen is in the chest, emesis is appropriate.

Generally, for inducing emesis, Gudai San (Melon Seed Powder, containing Melonis Fructus and Vigna angularis) or light salt water or warm tea can be administered. If the patient is weak, Ren Shen Lu Tang (Ginseng Rhizome Decoction) can be used to induce emesis. If there is excessive phlegm, Erchen Tang (Two-Aged Phlegm Resolving Decoction, a formula for drying dampness and resolving phlegm) can be taken warm in one cup, followed by stimulating the throat with a finger to induce vomiting.

For elderly people who are frail, individuals with Xu Lao (Deficiency Consumption) and internal injury, women with blood deficiency before pregnancy or postpartum, and those with weak and small pulses, emesis is contraindicated.

Herbs such as Fangfeng (Saposhnikoviae Radix), Jiegeng (Platycodonis Radix), and Zhizi (Gardeniae Fructus), when decocted alone in warm water, can induce vomiting. This is because improper use of emesis damages the Yuan Qi (Original Qi) of the Upper Jiao, causing significant harm; thus, caution is essential.

In Taiyang Disease (disease affecting the Taiyang channel), chills and fever are expected. However, if spontaneous sweating occurs without chills or fever, and the guan pulse is fine and rapid, this is due to the error of the physician inducing emesis.

If emesis is induced within one or two days of illness, the abdomen feels hungry but eating is difficult; if induced on the third or fourth day, there is a dislike for congee, a desire for cold food, and regurgitation of morning food by evening, all resulting from the physician's erroneous use of emesis. This constitutes a minor deviation (Minor Reverse).

If emesis is used in Taiyang Disease, but the patient no longer feels chills and dislikes wearing clothes, this indicates internal heat (Internal Distress) caused by emesis.

In Shaoyin Disease, if food is vomited immediately upon entry, with distress in the heart and an urge to vomit but inability to do so, accompanied by cold extremities and a wiry-slow pulse at the onset, this indicates excess in the chest and purgation is contraindicated. If there is cold fluid-rheum above the diaphragm causing dry heaves, emesis is also contraindicated; warming treatment should be used instead.

In Shaoyang Wind-Strike (Wind-strike affecting the Shaoyang channel), with deafness, red eyes, chest fullness, and irritability, emesis and purgation are contraindicated. Improper use of emesis or purgation will lead to palpitations and fright.

For patients with cold extremities and deficiency, women newly postpartum, and those with faint pulses, emesis is contraindicated.