咳谓无痰而有声，肺气伤而音不清；嗽谓无声而有痰，脾湿动而痰气侵；咳嗽谓有
痰有声，因伤肿气继动脾湿也。然痰之标在于脾，痰之本在于肾，故有宜燥剂以消之
者，有宜润剂以化之者。在小儿由风寒乳食者居多，宜从燥以消之，辛以豁之，半夏、
陈皮、前胡之类是也。《经》虽曰∶五脏六腑皆能令人咳，然必脏腑各受其邪，而与之
终不能离乎肺也。因痰而嗽者，痰为重主治在脾，因痰而动咳者，咳为重，主治在肺。
以时而论之，咳于春，春气上升也。咳于夏，火气炎上也。咳于秋，湿热伤肺也。咳
于冬，风寒外感也。以一昼夜而计之，清晨咳者属痰火；上昼嗽者属胃火；午后嗽者属
阴虚；黄昏嗽者，火气浮于肺经；五更嗽者，食积滞于三焦；肺实而嗽者，必顿嗽抱
首，面赤反食；肺虚而嗽者，必气逆虚鸣，颜白飧泻；肺热而嗽者，必痰腥而稠，身热
喘满。鼻干面红、手捏眉目鼻面。肺寒而嗽者，必嗽多痰薄，面白而喘，毛粟肠鸣，恶
风多绨。然嗽之为病，虽主乎肺，实从于心，心气过盛，则火烁金，治当抑心滋肺。
若脾气虚冷，则不能相生，是以肺气不足，风邪外袭，痰湿内生，治宜补其脾肺。若脾
实中痞，则热气上蒸，治宜泻脾清肺，故心乘肺为贼邪，肝乘为微邪，肾乘为实邪，脾
乘为虚邪，肺自病者，为正邪，凡一咳即出痰者，脾虚不胜湿而痰滑也。有连咳十数声
不出痰者，肺燥胜痰湿也。滑者，宜南星、半夏之属，燥其脾。若利气之剂，所当忌
也。涩者，宜枳壳、苏子、杏仁之属，利其肺。若燥脾之剂，所当忌也。大抵脾气不
足，则不能生肺家之气，风邪易感，故患肺寒者，皆脾虚得之。患肺热者，多脾实得
之。若至唇缩胸陷，喉有锯声，鼻干焦黑，咳嗽气粗，心腹胀痛者，死。若嗽久音哑，
直视手牵，鸦声腹胀，喘急多惊者，必变风候而死。若 而声嘶如锯，唇面皆青，项
下凹陷，涎如胶漆，口生腥臭，喘甚唇缩者，死。至于小儿百日内嗽，名为乳嗽，肺
叶尤娇，最易伤损，更须急治，久则血脉贯脸，两眶紫黑，或眼白红赤如血，谓之血
眼，当用生地、黑豆，共研成膏，掩于眼上，则眶黑自消，血随泪出而愈。
咳嗽是指没有痰液但有声音，这是肺气受损导致发音不清；嗽是指没有声音但有痰液，这是脾湿扰动导致痰气上逆；咳嗽则是有痰又有声音，是因为外邪损伤肺体后，继而触动脾湿所致。然而，痰的表象根源在于脾，痰的根本根源在于肾，因此有的情况适合用燥湿剂来消除痰湿，有的情况适合用润燥剂来化解痰浊。在小儿中，多由风寒或乳食积滞引起，适宜采用燥湿以消痰、辛散以豁痰的方法，如半夏、陈皮、前胡等药物。《黄帝内经》虽然说五脏六腑都能让人咳嗽，但必定是脏腑各自受到邪气侵袭，而最终都离不开肺的影响。因痰引起的嗽，痰是主要矛盾，治疗重点在脾；因痰引发咳的，咳是主要矛盾，治疗重点在肺。
从时间角度来看：春季咳嗽，是因为春气上升；夏季咳嗽，是因为火气炎上；秋季咳嗽，是因为湿热伤肺；冬季咳嗽，是因为风寒外感。
从一昼夜的时间来看：清晨咳嗽属于痰火；上午（上昼）嗽属于胃火；午后嗽属于阴虚；黄昏时嗽，是火气浮越于肺经；五更时分嗽，是食积停滞在三焦。
肺实导致的嗽，必然表现为顿咳抱头，面色发红却想进食；肺虚导致的嗽，必然表现为气逆虚鸣，面色苍白且伴有完谷不化的腹泻；肺热导致的嗽，必然表现为痰液腥臭且粘稠，身体发热、气喘胸闷，鼻子干燥、面色红赤、手揉眉目鼻面部位；肺寒导致的嗽，必然表现为咳嗽多、痰液稀薄，面色白且气喘，皮肤起鸡皮疙瘩、肠鸣音明显，怕风且多汗。
然而，嗽这种病，虽然主要责之于肺，实际上也源于心。如果心气过盛，火热会灼伤肺金，治疗应当抑制心火、滋养肺阴。如果脾气虚冷，则不能相生助肺，导致肺气不足，风邪外袭，痰湿内生，治疗应当补益脾肺。如果脾实导致中焦痞塞，热气上蒸，治疗应当泻脾清肺。因此，心乘肺为贼邪，肝乘肺为微邪，肾乘肺为实邪，脾乘肺为虚邪，肺自病为正邪。凡是咳嗽一声就吐出痰液的，是脾虚不胜湿邪而痰滑；连续咳嗽十几声却吐不出痰的，是肺燥胜过痰湿。对于痰滑者，适宜使用南星、半夏这类药物燥湿健脾，此时应当忌用利气之剂；对于痰燥涩者，适宜使用枳壳、苏子、杏仁这类药物利肺，此时应当忌用燥脾之剂。
大抵脾气不足，就不能生养肺家之气，容易感受风邪，所以患肺寒病的，都是因脾虚所致；患肺热病的，多因脾实所致。如果出现嘴唇收缩、胸部凹陷、喉间有拉锯声、鼻子干燥焦黑、咳嗽气粗、心胸腹胀痛的症状，预后不良，属死证。如果咳嗽日久导致声音嘶哑，眼睛直视、手脚抽搐，发出乌鸦般的叫声、腹部胀满、气喘急促且易受惊扰的，必然会转变为风证而死。如果出现声音嘶哑如拉锯声，嘴唇面部皆青紫，颈部下方凹陷，唾液像胶漆一样粘稠，口中有腥臭味，气喘严重且嘴唇收缩的，也是死证。至于小儿在百天之内发生的咳嗽，名为“乳嗽”，因为小儿肺叶尤为娇嫩，最容易受伤损，必须紧急治疗。如果拖延日久，血脉会贯通脸部，眼眶周围呈现紫黑色，或者眼白红赤如血，称为“血眼”。此时应当用生地黄、黑豆，共同研磨成膏状，敷盖在眼睛上，则眼眶发黑自然会消退，血液随眼泪排出而痊愈。
Cough (Ke) refers to a condition with sound but no phlegm, indicating injury to the Lung Qi resulting in unclear voice; Su refers to a condition with phlegm but no sound, caused by Spleen dampness stirring up phlegm qi. Cough and Su together refer to having both phlegm and sound, resulting from external pathogens damaging the Lung tissue, which subsequently stirs up Spleen dampness. However, the manifestation of phlegm lies in the Spleen, while its root lies in the Kidney. Therefore, some cases are suitable for treatment with drying agents to eliminate phlegm, while others require moistening agents to resolve it. In children, this is mostly caused by Wind-Cold or milk/food stagnation, and should be treated with drying methods to eliminate phlegm and acrid methods to disperse it, using herbs such as Banxia (Pinelliae Rhizoma), Chenpi (Citri Reticulatae Pericarpium), and Qianhu (Peucedani Radix). Although the *Classic* states that all five Zang and six Fu organs can cause cough, they must each receive their respective pathogens, yet ultimately cannot depart from the influence of the Lung. When Su is caused by phlegm, phlegm is the primary issue, and treatment focuses on the Spleen; when Cough is triggered by phlegm, Cough is the primary issue, and treatment focuses on the Lung.
From the perspective of seasons: Cough in Spring is due to the rising of Spring Qi; Cough in Summer is due to the flaming upward of Fire Qi; Cough in Autumn is due to Damp-Heat injuring the Lung; Cough in Winter is due to external contraction of Wind-Cold.
From the perspective of a 24-hour cycle: Cough in the early morning belongs to Phlegm-Fire; Su in the late morning belongs to Stomach Fire; Su in the afternoon belongs to Yin Deficiency; Su at dusk indicates Fire Qi floating in the Lung Meridian; Su at Wugeng (3–5 AM) indicates food stagnation in the San Jiao.
Cough due to Lung Excess must present with paroxysmal coughing while holding the head, red face, and desire to eat despite illness; Cough due to Lung Deficiency must present with rebellious Qi and empty wheezing, pale complexion, and undigested stool diarrhea; Cough due to Lung Heat must present with fishy-smelling and thick phlegm, fever, panting, chest fullness, dry nose, red face, and rubbing of the eyebrows, eyes, nose, and face; Cough due to Lung Cold must present with frequent coughing, thin phlegm, pale face, panting, gooseflesh skin, borborygmus, aversion to wind, and excessive sweating.
However, although Su primarily concerns the Lung, it actually originates from the Heart. If Heart Qi is excessive, Fire will scorch Metal (Lung), and treatment should suppress the Heart and nourish the Lung. If Spleen Qi is deficient and cold, it fails to generate support for the Lung, leading to insufficient Lung Qi, external invasion of Wind Pathogens, and internal generation of Phlegm-Dampness; treatment should tonify the Spleen and Lung. If Spleen Excess causes middle jiao blockage and steaming heat rises upward, treatment should drain the Spleen and clear the Lung. Thus, Heart overacting on Lung is considered "Thief Evil," Liver overacting on Lung is "Minor Evil," Kidney overacting on Lung is "Solid Evil," Spleen overacting on Lung is "Deficient Evil," and Lung self-disease is "Correct Evil." Those who expel phlegm immediately upon one cough have Spleen Deficiency unable to control dampness, resulting in slippery phlegm; those who cough continuously for ten-plus times without expelling phlegm have Lung Dryness overcoming Phlegm-Dampness. For slippery phlegm, use Arisaemae Rhizoma (Nanxing) and Pinelliae Rhizoma (Banxia) to dry the Spleen; at this time, Qi-moving agents should be avoided. For dry/sticky phlegm, use Aurantii Fructus (Zhike), Perillae Fructus (Suzi), and Armeniacae Semen Amarum (Xingren) to benefit the Lung; at this time, Spleen-drying agents should be avoided.
Generally, if Spleen Qi is insufficient, it cannot generate Lung Qi, making one susceptible to Wind Pathogens; thus, cases of Lung Cold are all due to Spleen Deficiency. Cases of Lung Heat are mostly due to Spleen Excess. If symptoms include retracted lips, sunken chest, saw-like sounds in the throat, dry and scorched-black nose, rough coughing breath, and abdominal distension and pain, it is a death prognosis. If chronic cough leads to hoarseness, staring eyes, hand pulling/twitching, crow-like vocalization, abdominal distension, rapid panting, and frequent fright, it will inevitably transform into a Wind syndrome and result in death. If there is hoarseness like a saw, cyanosis of lips and face, depression below the neck, saliva as sticky as glue, foul odor in the mouth, severe panting with retracted lips, it is also a death prognosis. As for cough occurring within the first hundred days of life, named "Milk Cough" (Ru Sou), the Lung leaves are particularly delicate and easily injured, requiring urgent treatment. If delayed, blood vessels will penetrate the face, causing purple-black circles around the eyes, or the whites of the eyes turning red like blood, called "Blood Eyes." At this point, use Shengdi Huang (Rehmanniae Radix) and Heidou (Phaseoli Semen Nigrum), ground together into a paste, applied over the eyes, so that the dark circles will naturally disappear, and the blood will exit with tears, leading to recovery.