Ingredient Mineral (矿物 kuàng wù)

Po Xiao

Mirabilite (Glauber's salt) · 朴硝

Mirabilite · Natrii Sulfas

Also known as: Pi Xiao (皮硝), Yan Xiao (盐硝)

Pu Xiao is a natural mineral salt (Glauber's salt) used in Chinese medicine as a gentle purgative to relieve constipation and soften hard stool, especially when there are signs of heat like fever and thirst. It is also applied externally as a paste to reduce swelling from breast abscesses, boils, and sore eyes.

Category Purgatives (攻下药) Substances for external application (外用药)
Therapeutic focus Digestive health Constipation relief Breast health Skin health

TCM Properties

Temperature

Cold

Taste

Bitter (苦 kǔ), Salty (咸 xián), Acrid / Pungent (辛 xīn)

Channels entered

Stomach, Large Intestine

Parts used

Mineral (矿物 kuàng wù)

Educational content • Consult qualified TCM practitioners for diagnosis and treatment

What This Ingredient Does

Every ingredient has a specific set of actions — here's what Po Xiao does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Po Xiao is primarily used to support these areas of health:

Digestive health Constipation relief Breast health Skin health

TCM Actions

In TCM terminology, these are the specific therapeutic actions that Po Xiao performs to restore balance in the body:

Purges Heat and unblocks the bowels Softens hardness and moistens dryness Clears Heat and reduces swelling Breaks blood stasis and promotes menstruation Resolves abscesses and discharges pus

How these actions work

Purges Heat and unblocks the bowels: Pu Xiao is a cold mineral salt that draws fluid into the intestines, creating a flushing action that expels retained heat and dry stool. It is used for constipation with dry, hard stools and abdominal fullness due to internal heat.

Softens hardness and moistens dryness: Its salty taste has a softening effect, helping to break down hard masses and move dry, impacted stool. It is especially effective for dry-type constipation where the stool is pellet-like.

Clears Heat and reduces swelling: Applied topically as a paste or wash, Pu Xiao cools and disperses local heat and swelling, making it useful for breast abscesses, sore throat, and red, swollen eyes.

Breaks blood stasis and promotes menstruation: By cooling the blood and moving stasis, Pu Xiao can help to unblock menstruation when there is heat-induced stagnation, and is used for postpartum retained lochia.

Resolves abscesses and discharges pus: Its ability to draw out heat and toxins promotes the resolution of pus-filled swellings and assists in healing.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony. Po Xiao is used to help correct these specific patterns.

Why Po Xiao addresses this pattern

Pu Xiao's cold, salty nature directly targets the Yang Ming fu organs (Stomach and Large Intestine) where excess heat has accumulated and dried fluids, causing hard stool and constipation. It draws fluid into the intestines to flush out heat and soften the fecal masses, relieving abdominal distension, dry stool, and fever typical of this pattern. Its bitter taste also descends, aiding the purging action.

A practitioner would look for one or more of these signs

Constipation

Dry, hard, difficult-to-pass stool

Abdominal Distention

Abdominal fullness worsened by pressure

Fever

High fever with aversion to heat

Thirst

Intense thirst with desire for cold drinks

Commonly Used For

These are conditions where Po Xiao is frequently used — but only when they arise from the specific patterns it addresses, not in all cases

Arises from: Heat in Yang brightness Organs

TCM Interpretation

In TCM, constipation with dry, hard stool and signs of heat (fever, thirst, yellow tongue coat) is seen as an accumulation of excess heat in the Yang Ming organs (Stomach and Large Intestine). The heat dries up fluids, causing the stool to harden and become difficult to pass. This excess-type constipation requires a purgative that clears heat and also moistens and softens the impacted stool.

Why Po Xiao Helps

Pu Xiao's cold nature clears the internal heat, and its salty taste acts as an osmotic agent to draw water into the intestine, softening the hard stool and flushing it out. It directly addresses both the heat and dryness, providing a thorough bowel clearance.

Also commonly used for

Carbuncles

Cooling external application disperses toxic-heat and promotes healing of boils

Conjunctivitis

Used in eye washes to relieve red, swollen, painful eyes

Ingredient Properties

Every ingredient has an inherent temperature, taste, and affinity for specific channels — these properties determine how it interacts with the body

Temperature

Cold

Taste

Bitter (苦 kǔ), Salty (咸 xián), Acrid / Pungent (辛 xīn)

Channels Entered

Stomach Large Intestine

Parts Used

Mineral (矿物 kuàng wù)

Dosage & Preparation

These are general dosage guidelines for Po Xiao — always follow your practitioner's recommendation, as dosages vary based on the formula and your individual condition

Standard dosage

外用适量。内服须提纯制成芒硝后使用，常用量6-12g。

Maximum dosage

内服最大剂量不超过12g（芒硝剂量）。外用不限。

Dosage notes

朴硝为粗制品，多作外用，如敷贴消肿。内服必须用其精制品芒硝，常用量6-12g，冲入药汁或开水溶化后服用，不入煎剂。

Preparation

内服时不可与其他药材同煎，宜冲入药汁或开水溶化后服用。外用可研末调敷或化水洗。

Processing Methods

In TCM, the same ingredient can be prepared in different ways to change its effects — here's how processing alters what Po Xiao does

Processing method

取朴硝100斤，用萝卜10-20斤切片，加水共煮，至完全溶化，过滤，放冷，析出上层结晶，干燥即得。

How it changes properties

经萝卜共煮后，杂质减少，药性较朴硝缓和，毒性降低，但仍为寒性泻下药。

When to use this form

用于实热便秘、大便燥结、积滞腹痛等内服证。

Common Ingredient Pairs

These ingredients are traditionally combined with Po Xiao for enhanced therapeutic effect

Da Huang
Da Huang Pu Xiao 9–12g : Da Huang 6–12g (Pu Xiao is dissolved in the decoction after cooking)

Together they powerfully purge heat and unblock the bowels. Da Huang clears heat and drives downward, while Pu Xiao softens the hard, dry stool and moistens the intestine, greatly enhancing the laxative effect for severe constipation with heat.

When to use: Severe Yang Brightness organ excess with dry, impacted stool, abdominal distension, and high fever (Da Cheng Qi Tang strategy).

Gan Cao
Gan Cao Pu Xiao 6–9g : Gan Cao 6g

Gan Cao moderates Pu Xiao's harsh cold nature, protecting the stomach and preventing excessive purgation while still allowing gentle laxation. This makes the purgative action more tolerable for patients with weaker digestion.

When to use: When a patient with heat constipation also has a weak Spleen or Stomach, or when a formula needs to be balanced to avoid injury to the middle burner.

Ji Nei Jin
Ji Nei Jin Pu Xiao 6–9g : Ji Nei Jin 10–15g

This pair enhances softening and stone-dissolving action. Ji Nei Jin's ability to dissolve masses and stones is amplified by Pu Xiao's saline softening effect, making it useful for flushing out stones and reducing accumulations.

When to use: Damp-Heat or stone patterns with urinary stones or gallstones, especially when there is accompanying heat and swelling.

Zhi Shi
Zhi Shi Pu Xiao 9g : Zhi Shi 6–9g

Zhi Shi breaks qi stagnation and forcefully downwardly directs qi, while Pu Xiao softens and purges. Together they powerfully move stuck qi and stool, relieving severe abdominal distension and pain.

When to use: Constipation with marked abdominal distension and pain, where both qi stagnation and dry stool are prominent.

Comparable Ingredients

These ingredients have overlapping uses — here's how to tell them apart

Mang Xiao
Po Xiao vs Mang Xiao

Both are from the same mineral, but Mang Xiao is the refined, purer form used primarily for internal purgation and softening; Pu Xiao contains more impurities and is often used externally or as a cheaper substitute when a milder action is acceptable.

Da Huang
Po Xiao vs Da Huang

Both purge heat from the bowels, but Pu Xiao's action is specifically softening and moistening dry, hard stool, while Da Huang clears heat and moves the bowels more aggressively without the moisturizing effect. Pu Xiao is preferred when the primary issue is dry, pellet-like stool.

Identity & Adulterants

Related species and common adulterations to be aware of when sourcing Po Xiao

朴硝常与芒硝、玄明粉、硝石等混淆。朴硝为粗制品，杂质较多，不可内服；芒硝为精制品，可内服。硝石（火硝）为硝酸钾，与朴硝不同，应区分。

Educational content — always consult a qualified healthcare provider or TCM practitioner before using any ingredient.

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Po Xiao

Slightly toxic

朴硝含杂质较多，黄色者伤人，红色者杀人。内服必须经提纯制成芒硝后方可使用。过量服用可引起剧烈腹泻、脱水、电解质紊乱。外用时避免用于皮肤破损处。

Contraindications

Situations where Po Xiao should not be used or requires extra caution

Avoid

脾胃虚寒、大便溏泄者忌服。

Avoid

孕妇禁用。

Caution

无实热积滞者不宜使用。

Caution

年老体弱者慎用。

Classical Incompatibilities

Traditional Chinese pharmacological incompatibilities — herbs or substances to avoid combining with Po Xiao

十九畏：硫黄畏朴硝。不宜与硫黄同用。

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

孕妇禁用。朴硝有泻下作用，可刺激子宫平滑肌收缩，增加流产或早产风险。

Breastfeeding

哺乳期慎用。朴硝可经乳汁分泌，可能引起婴儿腹泻。

Children

儿童禁用。朴硝性寒峻下，易伤脾胃，引起腹泻、脱水。

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Po Xiao

与利尿剂合用可能增加电解质紊乱风险。与其他泻下药合用可能增强泻下作用，导致脱水。

Dietary Advice

Foods and dietary considerations when taking Po Xiao

服药期间忌食生冷、油腻、辛辣食物，以免加重脾胃负担。

Botanical Description

Physical characteristics and morphology of the Po Xiao source mineral

朴硝为硫酸盐类矿物芒硝族芒硝（Mirabilite）经初步加工而成的粗制品，主要成分为含水硫酸钠（Na2SO4·10H2O），并含有少量氯化钠、硫酸钙、硫酸镁等杂质。天然产于内陆盐湖、海滨盐滩及含硫酸钠的土壤中，经溶解、过滤、冷却后析出的下层结晶即为朴硝。呈白色或黄白色结晶性颗粒或粉末，质脆易碎，易风化，无臭，味苦咸。因其杂质较多，多作外用，内服须进一步精制。

Sourcing & Harvesting

Where Po Xiao is sourced, when it's harvested or collected, and how to assess quality

Harvesting season

全年可采，以冬季低温时结晶较好。

Primary growing regions

主产于河北、天津、山东、河南、江苏、安徽等沿海及内陆盐碱地区，以四川、内蒙古、新疆等地盐湖所产为佳。

Quality indicators

以无色透明、结晶完整、无杂质者为佳。黄者伤人，赤者杀人，不可药用。

Classical Texts

Key passages from the classical Chinese medical texts that describe Po Xiao and its therapeutic uses

《本草纲目·石部·朴硝》载：“朴硝，苦、寒、无毒。主治百病，除寒热邪气，逐六腑积聚，结固留癖。能化七十二种石。炼饵服之，轻身神仙。”又云：“朴硝是初采得一煎而成者，未经再炼，故曰朴硝。可以熟生牛马皮，及治金银有伪。”李时珍按：“硝有三品：生西蜀者，俗呼川硝，最胜；生河东者，俗呼盐硝，次之；生河北、青、齐者，俗呼土硝。皆生于斥卤之地，彼人刮扫煎汁，经宿结成，状如末盐，犹有沙土猥杂，其色黄白，故《别录》云：朴硝黄者伤人，赤者杀人。”

Historical Context

The history and evolution of Po Xiao's use in Chinese medicine over the centuries

朴硝之名首载于《神农本草经》，列为上品。古代医家对朴硝、芒硝、硝石等名称多有混淆，至明代李时珍在《本草纲目》中详细考证，指出朴硝、芒硝、马牙硝实为一物，因加工精粗不同而名称各异。唐代以前多用硝石（火硝），宋代以后逐渐以芒硝取代。朴硝因杂质较多，古代主要用于外敷消肿，或用于熟制皮革。现代临床中，朴硝多作为芒硝的原料，经萝卜共煮精制后使用。其名称源于“见水即消，又能消化诸物”之意。