Herb Whole plant / Aerial parts (全草 quán cǎo)

Fu Ping

Duckweed · 浮萍

Spirodela polyrrhiza (L.) Schleid. · Herba Spirodelae

Also known as: Shui Ping (水萍), Fu Ping Cao (浮萍草), Tian Ping (田萍)

Images shown are for educational purposes only

Duckweed (Fu Ping) is a cooling surface-releasing herb that gently disperses wind-heat, encourages sweating, brings out rashes, stops itching, and helps eliminate excess fluid through urination. It is commonly used for early-stage wind-heat common cold, measles with incomplete eruption, hives, and acute edema.

TCM Properties

Temperature

Cold

Taste

Acrid / Pungent (辛 xīn)

Channels entered

Lungs, Urinary Bladder

Parts used

Whole plant / Aerial parts (全草 quán cǎo)

Educational content Consult qualified TCM practitioners for diagnosis and treatment

What This Herb Does

Every herb has a specific set of actions — here's what Fu Ping does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Fu Ping is primarily used to support these areas of health:

TCM Actions

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

How these actions work

Releases the exterior and promotes sweating: Fu Ping's acrid and cooling nature disperses wind-heat from the surface, making it useful for the early stages of wind-heat common cold with fever, mild chills, and absence of sweating. It provides a gentle but effective diaphoresis.
Promotes measles eruption: Fu Ping encourages the outward expression of rashes when they are slow to appear, which prevents deeper complications. It is a classic remedy for measles where the rash is not surfacing fully.
Dispels wind and relieves itching: Its light, floating quality reaches the skin to relieve itching from wind-heat or damp-heat conditions such as urticaria, eczema, and pruritus.
Promotes urination and reduces edema: By entering the Lung and Urinary Bladder channels, it helps regulate water metabolism. It reduces acute edema, especially when swelling occurs suddenly with wind-heat exterior symptoms.
Clears heat and resolves toxin: Applied topically or taken internally, Fu Ping clears heat and toxins for sores, boils, erysipelas, and burns in their early stages when redness and swelling predominate.

Patterns Addressed

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

Why Fu Ping addresses this pattern

Fú Píng's acrid-cold nature releases the exterior and clears heat, directly addressing wind-heat invading the surface. Its light, floating property promotes sweating without harshly dispersing, relieving fever, headache, and absence of sweating that characterize this pattern. It also benefits the throat and eyes.

A practitioner would look for one or more of these signs

Fever

Fever and slight chills

Anhidrosis

Absence of sweating

Headaches

Headache and body aches

Sore Throat

Sore throat

Commonly Used For

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

Arises from: Exterior-Heat

TCM Interpretation

Urticaria, especially acute episodes with red, raised wheals and intense itching, is seen as wind-heat invading the skin. The pores become obstructed, and the wind fighting in the superficial layers produces redness and itchiness. If dampness is mixed in, the wheals may be more swollen and exudative.

Why Fu Ping Helps

Fú Píng's acrid-cold nature dispels wind-heat from the exterior, while its light, floating quality guides it to the skin. It opens the pores, promoting sweating, which vents the wind pathogen and stops the itching. Its diuretic action also clears damp-heat that can accompany the rash.

Also commonly used for

Eczema

Dries dampness and calms itching for weeping eczema

Pruritus

Relieves skin itching from wind-heat or damp-heat

Edema

Promotes urination to reduce acute edema

Herb Properties

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

Temperature

Cold

Taste

Acrid / Pungent (辛 xīn)

Channels Entered

Lungs Urinary Bladder

Parts Used

Whole plant / Aerial parts (全草 quán cǎo)

Dosage & Preparation

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

Standard dosage

6–12 g dried (15–30 g fresh)

Maximum dosage

Dried herb: up to 15 g in certain acute presentations under close clinical supervision. Fresh herb: up to 30 g. Higher doses are sometimes used temporarily for severe wind-heat urticaria or acute nephritic edema with exterior symptoms, but only by experienced practitioners.

Dosage notes

Lower doses (3–6 g) are often sufficient for promoting rash eruption and releasing mild exterior heat. Higher doses (9–12 g, or up to 15 g) are used for stronger diaphoretic and diuretic effects in acute edematous states with a concurrent exterior pattern. Because the herb's action is light and dispersing, prolonged high-dose use is generally avoided.

Preparation

Add near the end of decoction (后下, hòu xià) and simmer briefly, as prolonged boiling may dissipate its light, volatile constituents responsible for releasing the exterior and venting rashes. For topical use, it is often decocted and applied as a wash or pounded fresh into a paste.

Common Herb Pairs

These ingredients are traditionally combined with Fu Ping for enhanced therapeutic effect

Niu Bang Zi

Fu Ping and Niu Bang Zi both disperse wind-heat and promote eruption; together they strongly encourage measles to surface and relieve itching, while Niu Bang Zi additionally benefits the throat and clears heat.

When to use: Wind-heat exterior pattern with fever, sore throat, and sluggish measles eruption or itchy rash.

Bo He
Bo He 1:1

Both are acrid-cool exterior-releasing herbs. Bo He's aromatic nature clears the head and eyes, while Fu Ping's floating nature promotes sweating. Together they relieve wind-heat headache, fever, and early-stage measles.

When to use: Wind-heat common cold with fever, headache, red eyes, and slight chills.

Chan Tui
Chan Tui Fu Ping 6g : Chan Tui 3–6g

Both facilitate eruption of the measles rash and calm itching. Chan Tui also clears wind-heat from the eyes and throat, while Fu Ping strengthens diaphoresis.

When to use: Measles with inadequate eruption, pruritic rash, and sore throat.

Comparable Ingredients

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

Bo He
Fu Ping vs Bo He

Both are acrid-cool exterior-releasing herbs, but Bo He is more aromatic and better at clearing head and eyes, while Fu Ping is more diaphoretic and diuretic, making it preferable when there is significant absence of sweating or edema.

Niu Bang Zi
Fu Ping vs Niu Bang Zi

Both disperse wind-heat and promote eruption, but Niu Bang Zi especially benefits the throat and resolves toxicity, while Fu Ping is stronger at relieving itching and promoting urination. Choose Fu Ping when prominent itching or edema accompanies wind-heat.

Identity & Adulterants

Related species and common adulterations to be aware of when sourcing Fu Ping

Sometimes confused with Dà Fú Píng (大浮萍), which is the larger aquatic plant Pistia stratiotes (water lettuce). Da Fu Ping has much larger, thicker, spongy leaves and multiple roots, whereas authentic Fu Ping is tiny (3–6 mm) and possesses only a single slender root. The two species have different medicinal properties and are not interchangeable.

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

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Fu Ping

Non-toxic

The herb is classified as non-toxic in all major monographs. Fresh plants may contain trace cyanogenic glycosides and other secondary metabolites; long-term excessive consumption of unprepared fresh material could theoretically cause mild gastrointestinal upset or skin irritation. Properly dried and decocted material is considered safe. No human fatalities or severe poisoning events have been recorded.

Contraindications

Situations where Fu Ping should not be used or requires extra caution

Avoid

Exterior deficiency with spontaneous sweating (self-sweating due to a weak defensive exterior) is strictly prohibited because Fu Ping's strong dispersing and diaphoretic action will further dissipate Qi and fluids.

Caution

Blood deficiency with dry, itching skin or Qi deficiency wind-pain patterns — the herb's cold, dispersing nature can injure Yin and consume Qi.

Caution

Spleen and Stomach cold deficiency with loose stools — the cold nature may aggravate digestive weakness.

Avoid

Pregnancy — the herb's blood-moving and strongly dispersing actions may threaten the fetus.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

Contraindicated. Fu Ping's strong blood-moving and dispersing properties may disturb the fetus by affecting placental blood flow. Its use in pregnancy is generally avoided in traditional practice.

Breastfeeding

Not recommended during breastfeeding. Although no specific lactation studies exist, the herb's active constituents may be passed to the infant through breast milk, and its cold, dispersing nature is generally considered unsuitable for postpartum women and nursing infants.

Children

Fu Ping is used in children, especially to promote eruption in measles when the rash is slow to surface. Because the herb is cold and strongly dispersing, and because robust pediatric safety data are lacking, it should only be given under the guidance of a qualified practitioner and not for prolonged periods. Dosages are typically at the lower end of the adult range, adjusted by weight.

Dietary Advice

Foods and dietary considerations when taking Fu Ping

While taking Fu Ping for wind-heat or edema with exterior symptoms, avoid cold, raw, and greasy foods that can obstruct the exterior and interfere with the herb's dispersing and diaphoretic action.

Botanical Description

Physical characteristics and morphology of the Fu Ping source plant

Fu Ping is an extremely small, free-floating aquatic plant consisting of a flat, leaf-like frond (thallus) 3–6 mm long and 2–4 mm wide, green on the upper surface and sometimes purple underneath, with 1–5 fine parallel veins. A single delicate root 2–5 cm long dangles from the underside. The plant reproduces rapidly both vegetatively by budding from a basal pouch and sexually via tiny unisexual flowers. It forms dense green mats on still or slow-moving fresh water — ponds, rice paddies, ditches, and lakes — throughout temperate and tropical regions.

Sourcing & Harvesting

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

Harvesting season

June to September (summer to early autumn), when the plants are most abundant and have achieved full vegetative growth.

Primary growing regions

Widespread across China, thriving in freshwater ponds, rice paddies, ditches, and still-water lakes. It is not associated with a specific *daodi* (道地药材) terroir; rather, good-quality material is collected wherever the plant grows densely in clean water.

Quality indicators

Good-quality Fu Ping consists of dry, whole, unbroken fronds that are greenish-brown, crisp, and free from mud, other aquatic weeds, and mold. It should have a faint, clean herbal odor. A stale, musty smell or a softened, discolored appearance indicates poor storage or deterioration.

Classical Texts

Key passages from the classical Chinese medical texts that describe Fu Ping and its therapeutic uses

Shen Nong Ben Cao Jing (《神农本草经》, “Divine Farmer’s Materia Medica”)
Chinese: “主暴热身痒,下水气,胜酒,长须发,止消渴。久服轻身。”
Translation: “It governs acute heat and body itching, drains water-dampness, counteracts alcohol, promotes beard and hair growth, and stops wasting-thirst. Long-term use lightens the body.”

Ben Cao Yan Yi Bu Yi (《本草衍义补遗》, “Supplement to the Extension of the Materia Medica”) by Zhu Danxi
Chinese: “水萍,发汗优勝麻黄。”
Translation: “Water duckweed surpasses Ma Huang in inducing sweating.”

Ben Cao Gang Mu (《本草纲目》, “Compendium of Materia Medica”) by Li Shizhen
Chinese: “主治风湿麻痹,脚气,打扑伤损,目赤翳膜,口舌生疮,吐血、衄血,癜风、丹毒。”
Translation: “Mainly treats wind-dampness numbness, beriberi, traumatic injuries, red eyes with corneal opacity, mouth and tongue sores, vomiting of blood, nosebleed, vitiligo, and erysipelas.”

Historical Context

The history and evolution of Fu Ping's use in Chinese medicine over the centuries

The name 浮萍 (floating duckweed) vividly captures the herb's habit of drifting on the water's surface. First recorded in the Shen Nong Ben Cao Jing as a medium-grade drug, it was valued for its ability to vent heat, water, and wind from the body. During the Jin-Yuan period, the influential physician Zhu Danxi famously declared that its diaphoretic power exceeded that of Ma Huang (Ephedra), a remarkable comparison given Ephedra's reputation as the strongest external-release agent. Li Shizhen later consolidated its expansive clinical uses, noting its efficacy for a wide range of skin, musculoskeletal, and mucosal conditions. In modern times, Fu Ping remains a first-line herb for childhood measles with inadequate eruption and for urticarial itching due to wind-heat, carrying a legacy that bridges classical and contemporary practice.