Greater Heat Health: Rotten Grass Becomes Fireflies — Clear the Heart, Prevent Heatstroke, and the San-Fu Moxibustion Plaster
First pentad: rotten grass becomes fireflies; second: the earth is moist and the heat swelters; third: heavy rains fall in due season — at the hottest node of the year, the San-Fu medicinal plaster is in season.
「Greater Heat, the node of the sixth month. Shu means heat. Heat is divided into greater and lesser; the first node is lesser, the middle node is greater; at this time the heat is still small.」 (「大暑,六月节。暑,热也。就热之中分为大小,月初为小,月中为大,今则热气犹小也。」)
— Wu Cheng, Monthly Ordinances of the Seventy-Two Pentads (《月令七十二候集解》, Yuan dynasty)
「At Greater Heat, Heaven’s qi is far more fierce than at Lesser Heat; hence it is named ‘Greater’.」
— multiple Qing-edition commentaries on the Monthly Ordinances of the Seventy-Two Pentads (after the Dadai Liji · Xiaxiaozheng 疏义)
I. The Meaning of the Term: The Extreme of Heat — Hence “Greater”
1. Astronomy and Season
Greater Heat (Dashu, 大暑) is the twelfth of the twenty-four solar terms. The sun reaches celestial longitude 120°, and the node falls on 22–24 July. Greater Heat and Lesser Heat together mark the most torrid period of the year — at Greater Heat the heat is at its most intense: “the handle of the Dipper points to bing for Greater Heat; at this season Heaven’s qi is far more fierce than at Lesser Heat, hence the name ‘Greater’.”
2. The Three Pentads
| Pentad | Phenomenon | Explanation (after Monthly Ordinances of the Seventy-Two Pentads and Dadai Liji) |
|---|---|---|
| First | Rotten Grass Becomes Fireflies (腐草为萤) | 「Fireflies are small insects that fly at night; they are born from rotten grass and the roots of rotten bamboo. The ancients believed that rotting grass gave rise to fireflies; in fact, fireflies’ eggs are simply hatched.」 |
| Second | The Earth Is Moist and the Heat Swelters (土润溽暑) | 「‘Ru’ means damp; the earth’s qi is moist, so the vapour rises and becomes sweltering heat.」 |
| Third | Heavy Rains Fall in Due Season (大雨时行) | 「In the previous pentad the damp and heat rise and stew; in this pentad heavy rains fall in due season, thereby driving back the summer-heat.」 |
Within the three pentads, “the earth is moist and the heat swelters” points to the characteristic of Greater Heat — the sweltering of damp and heat — “溽” (rù): Shuowen Jiezi glosses it as “damp”; Shuowen Tongxun Dingsheng says “溽, heat”; “the earth is moist” together with “heavy rains fall in due season” makes explicit the seasonal rule: “heat is dispelled by rain.”
II. Classical Theory: The Three San-Fu and “Middle San-Fu”
1. What Are the “Three San-Fu”?
The “San-Fu” (三伏, Three Hidden Heats) is the collective name for “Initial San-Fu,” “Middle San-Fu,” and “Final San-Fu” — the hottest period of the year. The meaning of “fu” (伏): the Hanshu · Jiaosizhi (《汉书·郊祀志》) annotation says 「fu means that the yin qi is about to rise, pressing upon the residual yang and unable to ascend; hence it lies concealed; hence the name ‘fu-day’.」
The San-Fu are determined by the rule of “three Geng days after Summer Solstice” — already broached in the Shiji · Tianguanshu (《史记·天官书》) and inherited by the Hanshu. Zhang Shoujie of the Tang, in his Shiji Zhengyi (《史记正义》), clearly explains:
「‘Fu’ means concealed. The San-Fu: the third Geng day after Summer Solstice is the Initial San-Fu; the fourth Geng day is the Middle San-Fu; the first Geng day after the Start of Autumn is the Final San-Fu.」
Therefore the Middle San-Fu typically begins just before or after Greater Heat and ends before the Start of Autumn — Greater Heat sits at the very centre of the Middle San-Fu.
2. Greater Heat and “Summer-Heat-Warmth”
Wu Jutong of the Qing, in his Wenbing Tiaobian (《温病条辨》, 1798), established a special chapter on “Summer-Heat-Warmth” (暑温):
「Summer-Heat-Warmth is the disease of the very midst of summer. The form resembles cold damage, but the right pulse is surging and rapid; the left pulse is on the contrary smaller than the right; thirst is severe; the face is red; sweat pours out. This is called Summer-Heat-Warmth.」
He also states:
「Heat combines with damp-heat: when biased toward the heat of the heat, it is shu-wen (暑温); when biased toward the damp of the heat, it is shi-wen (湿温).」
Greater-Heat cultivation is, in essence, the prevention and care of “summer-heat-warmth.”
3. The Discrimination of Yang-Heat from Yin-Heat
Lei Feng of the Qing, in Shibing Lun (《时病论》, 1882), on the discrimination of “heat”:
「When the summer-heat presses upon a person, it is called Yang-Heat; when, on account of the heat, headache, abdominal pain, vomiting, or diarrhoea arise, it is called Yin-Heat.」
- Yang-Heat: most often caused by working in the blazing sun or running long distances;
- Yin-Heat: most often caused by over-using cold drinks or seeking coolth in the wind.
For the former, White Tiger Decoction and the like — clear and rescue the yin; for the latter, Xiangru Decoction and the like — dispel and warm the center. The two patterns differ markedly in their treatment; the cultivator of health cannot but discern them.
III. Four Essentials for Greater-Heat Health
1. Daily Life: Shun the Heat toward Shade; Retire Late and Rise Early
Gao Lian of the Ming, in Zunsheng Bajian · Chapter on the Regulation of the Four Seasons:
「In the month of Greater Heat, the heat is at its extreme. Dwell in empty halls, clean rooms, waterside pavilions, or under the shade of trees — in places that are clean and spacious; one will naturally feel cool and fresh. Better still is to regulate the breath and purify the mind, ever holding ice and snow in the heart; even the great heat will then be somewhat lessened.」
- 🟢 Noon rest — between 11:00 and 13:00 (wushi), close the eyes, sit quietly, or nap for 30 minutes. “The Heart Channel is on duty” — most suitable for nurturing the heart;
- 🟢 Bathe in warm water — 「Sweat issuing unilaterally will produce unilateral withering.」 (Suwen · Treatise on the Generation and Connection of Life and the Hostile Manifestations of Heaven, 《生气通天论》) After sweating, one must avoid wind and wash with warm water;
- 🟢 Retire late, rise early — enter sleep before 23:00 (zishi); rise around 5:00–6:00 (maoshi).
2. Diet: Clear Summer-Heat and Boost Qi; Sour-Sweet Transform Yin
“Clear summer-heat and boost the qi” is the overall framework of Greater-Heat dietary care. Wang Mengying (王孟英, 1808–1868) of the Qing, in his Suixi Bujian Yinshi Pu (《随息居饮食谱》, 1861), on mung bean:
「Mung bean, sweet and cool; boiled, it clears the gallbladder and nourishes the stomach; resolves summer-heat and stops thirst; disinhibits urination; stops diarrhoea and dysentery.」
Wu Jutong, in Wenbing Tiaobian, establishes “Qingluo Yin” (Clear the Collaterals Decoction):
「Fresh lotus-leaf margin two qian, fresh honeysuckle two qian, watermelon peel two qian, fresh hyacinth-bean flower one stalk, sponge-gourd peel two qian, fresh bamboo-leaf heart two qian. Two cups of water; boil down to one cup; two doses per day. For all mild cases in which summer-heat injures the qi-fen of the lung channel, this may be used.」
He also establishes “Qingshu Yiqi Tang” (Clear Summer-Heat and Boost the Qi Decoction):
「American ginseng, shihu (dendrobium), maidong (ophiopogon), coptis, bamboo leaves, lotus stem, zhimu (anemarrhena), gancao (glycyrrhiza), jingmi (polished rice), watermelon peel. Treats the pattern of summer-heat injuring both qi and fluids.」
Greater-Heat Seasonal Recipes:
🟢 Mung-Bean Soup (or Porridge)
「Wash the mung beans clean; put them in a soup-pot; add the mung beans as soon as the water begins to boil. Do not boil for long: when the colour is green and the soup is jade, that is the best. Boiling long will turn the colour dark and muddy and will lose its heat-clearing property.」
— Gao Lian, Zunsheng Bajian, method for mung-bean soup
Li Shizhen, in Bencao Gangmu:
「Mung bean — the flesh is level, the peel cold; it resolves the toxins of metals, arsenic, all herbs of every kind; it is best taken raw, ground, with water. It treats pox-toxins, swelling-abscesses, and summer-heat; all of these draw upon its heat-clearing function.」
🟢 Sour Plum Decoction (Suanmeitang, 酸梅汤)
The record of “sour plum decoction” originates in the Qing imperial kitchens. Zhu Yizun (朱彝尊, 1629–1709) of the Qing, in Shixian Hongmi (《食宪鸿秘》, 1698):
「Black plums half a jin; gancao (glycyrrhiza) four liang; white sugar one jin; a little cinnamon bark; a little dried ginger. Three large bowls of clear water; simmer down to one and a half bowls; strain off the dregs; bottle and store. Drink in the month of summer: generates fluids, stops thirst, dispels vexation.」
This is the earliest and most influential modern recipe for sour-plum decoction — sour-sweet transform yin, perfectly matching the pathology “summer-heat injures qi and fluids.”
🟢 Watermelon
Wang Mengying, in Suixi Bujian Yinshi Pu:
「Watermelon, sweet and cold; clears the lung and stomach; resolves summer-heat; dispels vexation and stops thirst; revives from drunkenness; treats throat-block and mouth-sores; disinhibits urination.」
🟢 Winter Melon
Bencao Gangmu:
「Winter melon, sweet and slightly cold; clears heat; disinhibits the small intestine; stops the wasting-thirst vexation; disinhibits urine and stool.」
“Three Dos and Three Don’ts” of Greater-Heat Diet:
| Do | Don’t | |
|---|---|---|
| 🟢 | Sour-sweet, clear and moistening: black plums, grapes, bayberries, peaches, plums | Rich, greasy, heavy: fried foods, red meat, butter |
| 🟢 | Clear-summer-heat beans: mung bean, red adzuki bean, hyacinth bean | Iced cold drinks: iced beer, iced water, iced cakes |
| 🟢 | Fresh of the season: watermelon, lotus root, lotus seed, water caltrop | Pungent-hot dispersing: mustard, hot pepper, pepper |
3. Emotions: “The Heart at Rest Is Naturally Cool”
Gong Tingxian, in Shoushi Baoyuan:
「In the month of summer one should regulate the breath and purify the mind, ever holding ice and snow in the heart. Greater Heat is especially so; the heart is the fire-organ, summer is the fire season, two fires flaring one against the other; one must therefore moderate desire and clear the heart.」
Greater-Heat Emotional Regulation:
- 🟢 Sit in stillness — “One moment of sitting in stillness is worth a hu of ginseng”; “closing the eyes and visualizing” clears heart-fire;
- 🟢 Listen to the qin — “Qin means restraint” (Baihu Tong, 《白虎通》); of the five notes of the ancient qin, 宫、商、角、徵、羽, the zhi note corresponds to fire, and “using the yu note to regulate it” achieves “fire and water in mutual aid”;
- 🟢 Avoid heat and seek shade — “In heat, qi disperses; in cold, qi gathers”; mountains and forests, tree shade, the water-side are most suited to dispelling the heat.
4. The San-Fu Plaster: The “External Therapy” of Greater Heat
The “San-Fu Plaster” (also called “Heaven Moxibustion” 天灸 or “San-Fu Moxibustion” 三伏灸) is the most characteristic TCM external therapy of the Greater-Heat season.
🌿 Origins
The name “Heaven Moxibustion” appears in Wang Zhizhong (王执中) of the Song, Zhenjiu Zisheng Jing (《针灸资生经》, 1220):
「Whenever one uses garlic, mud, mustard, or tribulus to apply to the skin, so that the area turns red and blisters, this is called Heaven Moxibustion.」
The explicit record of the “San-Fu Plaster” appears in Zhang Lu (张璐, 1617–1698) of the Qing, Zhangshi Yitong (《张氏医通》, 1695):
「For cold-asthma, moxibust Feishu, Gaohuang, and Tiantu; sometimes effective, sometimes not. In the middle of the three fu of the month of summer, the white-mustard-seed application method often yields results. Recipe: white mustard seed, clean powder, one liang; yanhusuo (corydalis), one liang; gansui (kansui), xixin (Asarum), each half a liang; grind together to a fine powder; add half a qian of musk; pound evenly; mix with ginger juice and apply to Feishu, Gaohuang, Bailao, and other points. After application there will be numbness and pain; do not remove it immediately; wait until three incense sticks have burned; only then may it be removed. Apply once every ten days; after three such applications, the root of the disease is removed.」
This formula is the ancestral formula of the “San-Fu Plaster” — the four ingredients “white mustard seed, yanhusuo, gansui, xixin“ have been used to this day, and are collectively known as “Zhang’s Four Ingredients.”
🌿 Indications
The traditional indications of the “San-Fu Plaster” centre on “yang-deficiency and cold-exuberance” in the respiratory system:
- 🟢 Cold-asthma (in remission);
- 🟢 Chronic bronchitis;
- 🟢 Allergic rhinitis;
- 🟢 Recurrent colds from a deficient body.
In the modern era, the “Catalogue of TCM Medical Techniques” (2013, National Administration of Traditional Chinese Medicine) formally incorporates the “San-Fu Plaster” under technical specifications for “moxibustion” and “point application”; the evidence-based data for its clinical application is steadily accumulating.
🌿 Contraindications and Notes
- 🟢 Contraindications: yin-deficiency with effulgent fire, acute exacerbation, pregnancy, skin allergy;
- 🟢 Duration of application: 1–2 hours for children, 4–6 hours for adults, until the skin turns red and feels hot — do not apply for too long;
- 🟢 Timing: once each at Initial San-Fu, Middle San-Fu, and Final San-Fu — three times in all — and three consecutive years constitute one course of treatment.
Editor’s Note: The “San-Fu Plaster” is a traditional external TCM therapy and must be administered by qualified physicians after pattern differentiation. Do not self-purchase plasters or delay proper treatment.
IV. Gao Lian’s “Greater-Heat Sitting Exercise”
Gao Lian, in Zunsheng Bajian · Chapter on the Regulation of the Four Seasons, records the Greater-Heat Sixth-Month-Middle Sitting Exercise:
「The circulation is governed by the third qi of Shaoyang; the hour corresponds to Hand-Taiyin Lung (Wet-Earth). Each day at chou and yin hours (1–5 a.m.), both fists press on the ground; turn the head back toward the shoulder; draw left and right, three to five times each; click the teeth, exhale and inhale, swallow the saliva.」
The principle: “Both fists press on the ground” — drawing the yin of the earth; “Turn the head back toward the shoulder” — moving the Du-channel to cross-connect yin and yang; “Click the teeth, exhale and inhale, swallow the saliva” — securing kidney-essence and nurturing lung-qi.
V. Common Ailments at the Season and Their Care
1. Emergency Treatment of Heatstroke
Heatstroke most commonly arises from working under the blazing sun with a sudden rise in body temperature; severe cases are called “Summer-Heat Reversal” (暑厥) or “Summer-Heat Desertion” (暑脱).
Ye Tianshi, in Lin Zheng Zhi Nan Yi An:
「Summer-heat injures the qi; the lung receives it first; the signs are fever, profuse sweat, thirst, red face; in severe cases, clouded spirit and convulsive reversal.」
Emergency Essentials (drawing on multiple editions of the Guidelines for the Prevention and Treatment of Heatstroke):
- 🟢 Move: shift to a cool, well-ventilated place;
- 🟢 Apply: soak a towel in cool water and apply to the head, neck, and armpits;
- 🟢 Drink: dilute salt water or mung-bean soup;
- 🟢 Press: Renzhong (人中), Hegu (合谷), Neiguan (内关);
- 🟢 Send: those with clouded spirit or convulsive reversal must be sent to hospital urgently.
2. “Summer-Dysentery and Diarrhoea”
In the sweltering damp of Greater Heat, dysentery is common. Wang Mengying, in his Huoluan Lun (《霍乱论》, 1838):
「Patterns of sudden turmoil (huoluan) — damp-heat are many, cold-damp are few.」
Care:
- 🟢 Huoxiang Zhengqi San;
- 🟢 Cook porridge with mung bean, hyacinth bean, Job’s-tears;
- 🟢 “Abstain from raw, cold, and greasy food”;
- 🟢 Sour plum decoction can prevent diarrhoea.
VI. A Note on the Folk-Custom of “Fu Noodles and Fu Mutton”
The dietary customs of the old “fu days” are recorded in the late-Qing / early-Republican Qingbai Leichao (《清稗类钞》, Xu Ke, 1917):
「The custom of the North: dumplings at Initial Fu, noodles at Middle Fu, pancakes fried with egg at Final Fu. On the fu days all people suffer from the heat; this food opens the stomach and resolves the heat.」
There is also the folk custom of “Pengcheng fu-yang” (the summer mutton of Xuzhou) — in parts of Shandong and Xuzhou, Jiangsu, at Greater Heat there is a custom of eating mutton and drinking mutton soup: “eat fu-yang for one winter, and walk out unafraid of the wind”, based on the principle of “using heat to master heat”: sweating to expel toxins, warming the centre and supplementing the deficiency. This custom is widely recorded in local gazetteers of the late Qing and early Republican period; its origin and transmission still await further documentary investigation.
VII. Bibliography (selected)
- Huangdi Neijing · Suwen · Treatise on the Generation and Connection of Life and the Hostile Manifestations of Heaven (《素问·生气通天论》) and Treatise on Heat (《素问·热论》)
- Hanshu · Jiaosizhi, Ban Gu (111)
- Shiji · Tianguanshu, with Tang Zhang Shoujie’s Shiji Zhengyi
- Zhenjiu Zisheng Jing, Wang Zhizhong (1220)
- Taiping Huimin Heji Jufang, Chen Shiwen et al. (1078–1107)
- Bencao Gangmu, Li Shizhen (1578)
- Zunsheng Bajian, Gao Lian (1591)
- Zhenjiu Dacheng, Yang Jizhou (1601)
- Shoushi Baoyuan, Gong Tingxian (1615)
- Treatise on Life-Cultivation According to the Seasons, Qiu Chuji (Yuan, attr.) / Gao Lian (Ming, ed.)
- Zhangshi Yitong, Zhang Lu (1695) — the ancestral source of the San-Fu Plaster
- Shixian Hongmi, Zhu Yizun (1698) — earliest recipe for sour-plum decoction
- Lin Zheng Zhi Nan Yi An, Ye Tianshi (1746, compiled by his disciples)
- Wenbing Tiaobian, Wu Jutong (1798) — Qingluo Yin and Qingshu Yiqi Tang
- Huoluan Lun, Wang Mengying (1838)
- Shibing Lun, Lei Feng (1882)
- Suixi Bujian Yinshi Pu, Wang Mengying (1861)
- Qingbai Leichao, Republican-era Xu Ke (1917) — records of the “dumplings / noodles / pancakes” folk-custom of the three fu days
- Monthly Ordinances of the Seventy-Two Pentads, Wu Cheng (Yuan); multiple Qing editions by Lu Kuixun, Tang Zan’gong, etc.
- Modern compendia: Chinese Dietetics / TCM Dietetics, various editors
Qihuang Library · Solar Term Health · The heat is at its extreme; clear the heart and prevent heatstroke — the San-Fu Plaster, the fu-mutton, the sour-plum decoction — all are season-appropriate Greater-Heat practices.