Zi Su 紫苏 — Chinese Herbal Medicine

Zi Su (紫苏) At a Glance

• Herb: Zi Su
• Chinese name: 紫苏 (Zi Su)
• Latin name: Folium Perillae
• Nature: Warm
• Taste: Acrid
• Meridian: Lung
• Category: Acrid and warm exterior-releasing

Zi Su (紫苏, Folium Perillae) is the dried leaf (and sometimes tender stem) of Perilla frutescens (L.) Britt. (Lamiaceae), harvested in summer when the branches and leaves are lush. Its name — ‘purple revival’ — comes from the deep purple colour of its leaves (in the purple-leaf variety) and its ability to revive the Spleen-Stomach function. Zi Su is unique among exterior-releasing herbs: it simultaneously releases exterior Wind-Cold, harmonises the Middle Jiao and stops vomiting, and calms the restless fetus. This triple action makes it the premier herb for morning sickness accompanied by exterior symptoms, and for seafood-borne digestive disturbance. The plant yields three distinct medicinal parts: Zi Su Ye (leaf, for exterior release and antiemesis), Zi Su Geng (stem, for moving Qi), and Zi Su Zi (seed, for descending Lung Qi and transforming Phlegm). Zi Su is also widely used as a culinary herb in Japanese, Korean, and Southeast Asian cuisine (shiso).

Actions & Therapeutic Effects

• Releases the exterior and disperses Cold — treats Wind-Cold exterior syndrome, especially when accompanied by Spleen-Stomach disharmony with nausea, abdominal distension, and poor appetite.
• Harmonises the Middle Jiao and stops vomiting — primary action for Cold pattern nausea, vomiting, and morning sickness of pregnancy.
• Moves Qi and resolves the toxicity of fish and crab — digestive Qi stagnation from overconsumption of raw, cold, or seafood.
• Calms the fetus — treats restless fetus (胎动不安) from Qi stagnation or exterior Cold invasion.

Clinical Applications in TCM

• Wind-Cold common cold with Spleen-Stomach discomfort — combined with Sheng Jiang, Chen Pi, and Xing Ren (Xing Su San)
• Morning sickness of pregnancy from Cold stagnation — paired with Sheng Jiang and Sha Ren
• Seafood or crab poisoning with abdominal pain, vomiting, and diarrhoea — decocted alone or with Sheng Jiang
• Epigastric distension and belching from Cold-Qi stagnation — combined with Chen Pi and Sha Ren
• Cough from Wind-Cold with profuse sputum — used with Qian Hu, Xing Ren, and Jie Geng
• Hiccough and rebellious Qi from Cold in the Middle — Zi Su decoction with raw ginger

Precautions & Safety

• Dosage: 5–10 g in decoction; do not decoct for extended time (volatile oils disperse quickly) — add near the end of decoction
• Contraindicated in exterior Heat patterns, or Qi deficiency with profuse sweating
• Caution in patients with yin deficiency — the aromatic, drying quality may aggravate dry patterns
• Avoid large doses in patients taking anticoagulants (perilla oil contains alpha-linolenic acid with mild antiplatelet activity)
• Generally safe during pregnancy when indicated; standard doses are appropriate

Classical TCM Formulas

• Xing Su San (杏苏散): Xing Ren, Zi Su Ye, Qian Hu, Jie Geng, Zhi Qiao, Ban Xia, Chen Pi, Fu Ling, Gan Cao, Sheng Jiang, Da Zao — releases the exterior, disperses Cold, and stops cough. Source: Wen Bing Tiao Bian.
• Xiang Su San (香苏散): Xiang Fu, Zi Su Ye, Chen Pi, Zhi Gan Cao — releases the exterior, regulates Qi, and harmonises the Middle. Source: Tai Ping Hui Min He Ji Ju Fang.
• Zi Su Yin (紫苏饮): Zi Su, Da Fu Pi, Dong Gua Pi, Sang Bai Pi — promotes urination and reduces oedema in pregnancy (modern use: gestational hypertension). Source: Fu Ren Da Quan Liang Fang.
• Huo Xiang Zheng Qi San (藿香正气散): Huo Xiang, Zi Su Ye, Bai Zhi, Ban Xia, Hou Po, Chen Pi, Fu Ling, Bai Zhu, Da Fu Pi, Jie Geng, Gan Cao, Sheng Jiang, Da Zao — releases exterior, transforms Dampness, and regulates the Middle. Source: Tai Ping Hui Min He Ji Ju Fang.

Herb Combinations

• Zi Su + Sheng Jiang (生姜) + Chen Pi (陈皮): releases the exterior, harmonises the Stomach, and stops vomiting — the foundational combination for morning sickness. Source: Classical exterior-resolving formulas.
• Zi Su + Xing Ren (杏仁) + Qian Hu (前胡): disperses Lung Qi and stops cough from Wind-Cold. Source: Xing Su San (Wen Bing Tiao Bian).
• Zi Su + Sha Ren (砂仁) + Bai Zhu (白术): harmonises the Middle, calms the fetus, and treats restless fetus from Qi stagnation. Source: Tai Shan Pan Shi San.
• Zi Su + Huo Xiang (藿香) + Bai Dou Kou (白豆蔻): aromatically transforms Dampness, harmonises the Spleen-Stomach, and relieves nausea from Cold-Damp.
• Zi Su + Huang Lian (黄连) + Zhu Ru (竹茹): a balanced cold-warm pair — treats vomiting from mixed Cold-Heat patterns. Source: Classical harmonising prescriptions.

Pharmacology & Research

Antimicrobial: perillaldehyde and perilla alcohol demonstrate broad-spectrum antibacterial activity against Staphylococcus aureus, Escherichia coli, and various oral pathogens.
Antiemetic and gastrointestinal prokinetic: promotes gastric emptying and reduces nausea via modulation of 5-HT3 receptors and vagal afferent signalling.
Antioxidant: rosmarinic acid and luteolin derivatives provide strong free-radical scavenging activity; concentrated in the leaf.
Anti-allergic: rosmarinic acid inhibits mast cell degranulation and reduces IgE-mediated histamine release — relevant for allergic rhinitis and food allergy.
Anti-inflammatory: suppresses TNF-α, IL-6, and COX-2 expression via NF-κB pathway inhibition; perillaldehyde is the primary active compound.
Sedative and anxiolytic: perillaldehyde demonstrates GABAergic activity; inhalation of perilla essential oil reduces stress markers in human trials.

Classical Descriptions

• 《名医别录》(Ming Yi Bie Lu, circa 500 CE): “紫苏，味辛，温。主下气，除寒中，其子尤良。” (Zi Su: acrid, warm. Governs descending Qi and eliminates Cold in the Middle; the seed [Zi Su Zi] is especially effective.)
• 《本草纲目》(Bencao Gangmu, 1596) — Li Shizhen: “紫苏，近世要药也。其味辛，入气分；其色紫，入血分。故同橘皮、砂仁，则行气安胎；同藿香、乌药，则温中止痛；同香附、麻黄，则发汗解肌；同川芎、当归，则和血散血。” (Zi Su is a key medicine of recent times. Its flavour is acrid, entering the qi division; its colour is purple, entering the blood division. Therefore, with Chen Pi and Sha Ren it moves qi and calms the fetus. With Huo Xiang and Wu Yao it warms the Middle and stops pain. With Xiang Fu and Ma Huang it promotes sweating and releases the muscle layer. With Chuan Xiong and Dang Gui it harmonises blood and scatters [stasis].)
• 《本草备要》(Bencao Beiyao, 1694) — Wang Ang: “紫苏，辛温，发表散寒，行气宽中，安胎，解鱼蟹毒。” (Zi Su: acrid-warm; releases the exterior and scatters Cold; moves Qi and loosens the Middle; calms the fetus; resolves fish and crab poisoning.)