Jade Windscreen (Yu Ping Feng San) is an interesting formula because it has variations in its official dosage and classification. There is also disagreement about the earliest source text for this formula. Some sources list the 1347 CE text Dān Xī Xīn Fǎ (“Dān Xī's Heart-Approach”), while others list the lost text Jiū Yuán Fāng (“Investigations on Original Formulas”), which was written in 1213 CE and was found referenced in later extant texts. There is also disagreement about the doses of the medicinals, with some texts favoring higher amounts of huáng qí and other texts favoring higher amounts of bái zhú. Finally, some curriculum texts classify the formula under the supplementing chapter, while others classify it under the securing and astringing chapter.

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Yù Píng Fēng Sǎn (玉屏风散 Jade Windscreen Powder)

Source: Dān Xī Xīn Fǎ (“Dān Xī's Heart-Approach”).

Ingredients

Fáng fēng (防风 saposhnikovia, Saposhnikoviae Radix) 30 g
Huáng qí (黄芪 astragalus, Astragali Radix) 30 g
Bái zhú (白朮 white atractylodes, Atractylodis Macrocephalae Rhizoma) 60 g

Method: Grind and take 3 qián (9 g) of powder per dose, decocted in 1½ cups of water with three pieces of shēng jiāng (Zingiberis Rhizoma Recens). In the modern day, it is powdered and taken in 6–9 gram doses, twice per day with water. It can also be prepared as a decoction with a reduction in dosage.

Actions: Boosts qi, secures the exterior, and checks sweating.

Indications: Exterior vacuity spontaneous sweating, and easy contraction of wind evil.

Analysis

When defense qi is weak, it is unable to secure the exterior, so the interstices are loose and empty. Construction-yin cannot be safeguarded, so the fluids discharge outwards; this causes spontaneous sweating from exterior vacuity, as well as aversion to wind and a vacuous pulse.

When there is exterior vacuity and the qi is weak, the skin and hair are loose and slack. This allows for easy contraction of wind evil, causing common colds. The appropriate treatment is to boost qi, secure the exterior, and check sweating.

Huáng qí is regarded as the sovereign, and some texts indicate that its dosage should be equal to that of bái zhú. Huáng qí boosts qi and secures the exterior.

Bái zhú fortifies the spleen and boosts qi, and it assists huáng qí to strengthen the qi-boosting and exterior-securing effect. It is a minister.

The combination of these two medicinals fills the exterior so that sweat no longer discharges outward and evil no longer easily invades.

Fáng fēng moves to the exterior and dispels wind. It guards against wind evil and is used here as both an assistant and a courier.

When huáng qí is combined with fáng fēng, it is able to secure the exterior without retaining evil. When fáng fēng is combined with huáng qí, it dispels evil without damaging right. This complementary opposition provides supplementation within dispersing, and dispersing within supplementation.

This formula is named Jade Windscreen Powder because boosting qi, securing the exterior, and stopping the discharge of sweat protects against the invasion of wind evil. The name uses the analogy of blocking wind with a protective screen, and the word “jade” is used to indicate its value.

This formula and guì zhī tāng (Cinnamon Twig Decoction) both treat exterior vacuity spontaneous sweating, but yù píng fēng sǎn primarily reaches the exterior to secure the exterior and check sweating, and it primarily treats spontaneous sweating due to defense vacuity. By contrast, guì zhī tāng (Cinnamon Twig Decoction) regulates construction and defense, and is used to treat spontaneous sweating due to disharmony of construction and defense. Guì zhī tāng also resolves the exterior, so it is used to treat externally contracted wind-cold in exterior vacuity patterns.