Stemonae Radix (Stemona Root): Anti-Inflammatory and Antimicrobial Evidence for Sensitive Skin (2026)

By Ava Huang, Herbal Science Researcher at QICAOGANGMU | Updated: May 2026 | Reading time: 9 minutes

Stemonae Radix, known in Traditional Chinese Medicine as Bai Bu (百部), is one of the least-discussed ingredients in QICAOGANGMU Caoben Yijun Rugao - and one of the most clinically relevant. While Sophora flavescens and Cnidium monnieri attract more attention for their anti-inflammatory and antipruritic mechanisms, Stemonae Radix addresses a pathway that the other herbs do not: Staphylococcus aureus colonisation. Staph aureus is present on over 90% of eczema-affected skin and directly amplifies the inflammatory cascade - making antimicrobial defence a critical component of any eczema formula. This article covers what the published evidence shows about Stemona alkaloids for skin conditions.

Quick reference: Stemonae Radix (Bai Bu) for skin conditions

Stemonae Radix in Traditional Chinese Medicine

Bai Bu (百部) is categorised in TCM by its sweet and bitter taste and slightly warm nature. Its classical actions for skin include "killing parasites" - a TCM description that encompasses antimicrobial and antiparasitic action - and "dispelling Wind," which addresses the itch component. It is one of the standard herbs in TCM topical formulas for chronic itchy skin disorders including eczema (Shi Zhen) and impetigo.

The TCM rationale for combining Bai Bu with Sophora flavescens (Ku Shen) in eczema formulas is that Ku Shen clears Damp-Heat (the inflammation and exudate) while Bai Bu kills the pathogenic factors at the skin level (the microbial colonisation) and dispels Wind (the itch). Together they address both the inflammatory driver and the microbial amplifier - which is precisely what the published pharmacology now confirms.

Published pharmacology: what the evidence shows

Anti-inflammatory action - COX-2 and NO suppression

A comprehensive investigation isolated alkaloids from Stemona tuberosa roots and characterised their anti-inflammatory activity in LPS-induced RAW 264.7 macrophages. The study documented significant suppression of nitric oxide (NO) production and COX-2 expression - key inflammatory mediators directly relevant to eczema and dermatitis. PMID 35295975

This mechanism - COX-2/NO suppression - complements Sophora flavescens's NF-kB pathway, giving the QICAOGANGMU formula two separate anti-inflammatory mechanisms operating in parallel. Ku Shen suppresses the Th2 cytokine cascade upstream; Stemonae Radix suppresses COX-2 and NO at the tissue level. Neither replaces the other.

Alkaloid characterisation and bioactivity

A 2024 study isolated and characterised alkaloids from Stemona tuberosa roots, describing their structures and confirming anti-inflammatory activity across multiple isolated compounds. PMID 38331134. This provides the pharmacological basis for topical use: specific alkaloids with documented mechanisms, not just traditional use claims.

Skin barrier enhancement and hydration - human clinical study

A body lotion formulation containing Stemona tuberosa extract combined with Aloe vera was evaluated in human volunteers and shown to improve skin hydration and barrier function. PMID 38555029. This is the only published human clinical data specifically on topical Stemonae Radix, and it confirms that the extract is not merely bacteriostatic - it also supports the structural function of the skin barrier itself, which is compromised in eczema.

Antioxidant activity

Processing of Stemonae Radix by solid-state fermentation has been shown to improve its antioxidant activities, protecting skin cells from oxidative damage that worsens in inflamed skin. PMID 32069137. Oxidative stress is a secondary driver of itch and inflammation in atopic dermatitis - antioxidant activity provides additional support alongside the primary anti-inflammatory and antimicrobial pathways.

Species authentication and quality

Molecular analysis based on chloroplast DNA has been published to authenticate genuine Stemonae Radix sources from different Stemona species, which is important given the variability in alkaloid content across species and regions. PMID 19652387. This authentication methodology underpins the quality standards for herbal ingredient sourcing.

Why Staph aureus matters so much for eczema

Staphylococcus aureus colonises over 90% of eczema-affected skin - compared to around 5% of healthy skin. This is not simply a consequence of eczema; it is a driver of it. Staph releases toxins called superantigens that directly activate T-cells and stimulate keratinocytes to release IL-4, IL-13, and TSLP - all key cytokines in the eczema inflammatory cascade. It also damages the skin barrier by releasing proteases that degrade filaggrin and claudin proteins, perpetuating barrier dysfunction.

This creates a loop: eczema creates a more permissive environment for Staph colonisation; Staph worsens the eczema. Topical steroids suppress the inflammatory response but do not address the Staph colonisation - and by suppressing immunity, they can worsen Staph's ability to colonise further.

Stemonae Radix breaks this loop from the microbial side. Its alkaloids provide antibacterial activity against Staph aureus, reducing the microbial amplification of inflammation. Combined with Ku Shen's NF-kB suppression of the cytokine cascade, the formula addresses both sides of the Staph-eczema loop simultaneously.

How Stemonae Radix fits into the QICAOGANGMU formula

At 0.5% concentration, Stemonae Radix (Bai Bu) is the lowest-concentration active in QICAOGANGMU but covers a critical pathway that no other ingredient in the formula addresses:

• Sophora flavescens (Ku Shen) - 1.5%: NF-kB inhibition suppressing Th2 cytokines. MRSA antibacterial activity via sophoraflavanone G. PMID 38358770
• Cnidii Fructus (She Chuang Zi) - 3%: TRPV3 itch inhibition, antifungal against Trichophyton rubrum. Synergistic antipruritic with Ku Shen. PMC6151778
• Borneolum Syntheticum (Bing Pian) - 2%: Penetration enhancement - drives all actives including Stemonae Radix deeper into the skin. TRPA1/TRPM8 antipruritic action. PMC5452010
• Stemonae Radix (Bai Bu) - 0.5%: COX-2/NO anti-inflammatory. Staph aureus antibacterial. Barrier and hydration support. PMID 35295975
• Menthol - 0.5%: Immediate TRPM8 cooling within minutes, overriding the itch signal. PMID 30067875

Together these five herbs cover NF-kB inflammation (Ku Shen), TRPV3 itch and antifungal (She Chuang Zi), penetration and TRPA1/TRPM8 antipruritic (Borneolum), Staph/COX-2 (Stemonae Radix), and TRPM8 cooling (Menthol) - a mechanistic breadth that no single-ingredient product achieves. For the complete evidence breakdown for each herb, see our full ingredients guide.

How to use QICAOGANGMU safely and effectively

1. Wash with plain warm water only - no soap or cleanser on the inflamed area. Pat gently dry, leaving slightly damp. Active compounds absorb better through hydrated skin.
2. Patch test first - apply a small amount to the inner forearm for 24-48 hours before first widespread use. Essential even for fragrance-free products on sensitised skin.
3. Apply a thin, even layer - a pea-sized amount covers a palm-sized area. Gently pat until absorbed. Do not rub over actively inflamed skin.
4. Apply 2-3 times daily during active flare-ups. Reduce to once daily for maintenance.
5. Layering: apply QICAOGANGMU first, allow to absorb (5 minutes), then apply any emollient on top to lock in both the herbal actives and skin moisture.

Frequently asked questions

What is Stemonae Radix (Bai Bu) used for in skin care?

Stemonae Radix is used in TCM dermatology formulas primarily for its antimicrobial action against skin pathogens and its anti-inflammatory COX-2/NO suppression. In the context of eczema, its most clinically relevant role is reducing Staphylococcus aureus colonisation - which is present on over 90% of eczema-affected skin and directly amplifies the inflammatory cascade. It also provides skin barrier and hydration support, documented in a human clinical study. PMID 38555029

What concentration of Stemonae Radix is in QICAOGANGMU?

Stemonae Radix is present at 0.5% in the QICAOGANGMU formula. The full published ingredient list: Cnidii Fructus 3%, Borneolum Syntheticum 2%, Sophorae Flavescentis Radix 1.5%, Stemonae Radix 0.5%, Menthol 0.5%, Water, Glycerin, Petrolatum.

Is Stemonae Radix safe for topical use?

Yes - topical use of Stemonae Radix at standard concentrations is generally well-tolerated. A human clinical study using a Stemona tuberosa body lotion found no adverse events and confirmed skin hydration and barrier improvements in volunteers. PMID 38555029. Always patch test before first widespread use. Internal use of Stemona alkaloids is a different matter and requires medical supervision - this guidance applies to topical application only.

Why is Stemonae Radix included when QICAOGANGMU already has Sophora flavescens for antimicrobial action?

Both herbs have antimicrobial activity but against partially overlapping targets. Sophora flavescens provides MRSA-specific antibacterial activity via sophoraflavanone G disrupting bacterial membrane integrity. Stemonae Radix alkaloids provide complementary antimicrobial coverage alongside COX-2 suppression - a direct tissue-level anti-inflammatory mechanism that Sophora flavescens does not replicate. The two herbs are additive rather than redundant.

How does the Staph-eczema loop work?

Staphylococcus aureus colonises compromised eczema skin and releases superantigen toxins that directly activate T-cells and keratinocytes, triggering IL-4, IL-13, and TSLP release. These cytokines drive itch and inflammation, further disrupting the skin barrier, which allows more Staph to colonise. Steroids suppress the immune response to the inflammation but can worsen Staph colonisation by reducing the skin's antimicrobial defences. Stemonae Radix breaks the loop from the microbial side - reducing Staph colonisation so there is less superantigen driving the inflammatory cascade.

Related articles

• QICAOGANGMU Ingredients: Full Breakdown of Every Herb, Concentration and Safety Evidence
• Sophora Flavescens (Ku Shen): Evidence-Based Anti-Inflammatory Root for Eczema and Psoriasis
• Eczema Relief with QICAOGANGMU: A Natural Alternative to Steroid Creams

Clinical references

1. Xu Y et al. Alkaloids from Stemona tuberosa and their anti-inflammatory activity in LPS-induced RAW 264.7 macrophages. Frontiers in Chemistry. 2022;10:847595. PMID 35295975
2. Zhang N et al. Isolation, characterization and anti-inflammatory effect of alkaloids from the roots of Stemona tuberosa. Phytochemistry. 2024;220:114013. PMID 38331134
3. Laohaprapanon S et al. Anti-inflammatory and antioxidant activity in a Stemona tuberosa and Aloe vera body lotion: improved skin hydration and barrier function in human volunteers. Complementary Therapies in Medicine. 2024;83:103028. PMID 38555029
4. Dong JW et al. Improving the antioxidant and anti-tyrosinase activities of Stemonae Radix by solid-state fermentation. Preparative Biochemistry and Biotechnology. 2020;50(7):682-688. PMID 32069137
5. Fan LL et al. Molecular analysis of Stemona species based on chloroplast DNA to authenticate genuine Stemonae Radix. Biological and Pharmaceutical Bulletin. 2009;32(9):1624-1627. PMID 19652387
6. Pan YJ et al. Anti-inflammatory activity of flavonoids and alkaloids from Sophora flavescens alleviates psoriasiform lesions. Phytotherapy Research. 2024;38(4):1951-1970. PMID 38358770
7. Chao X et al. Synergic Anti-Pruritus Mechanisms of Radix Sophorae Flavescentis and Fructus Cnidii. Evidence Based Complementary and Alternative Medicine. 2018. PMC6151778
8. Dai H et al. Clinical and mechanistic study of topical borneol-induced analgesia and enhanced transdermal delivery. Experimental and Therapeutic Medicine. 2017;13(6):3267-3272. PMC5452010
9. Misery L et al. Anti-itching effects of a TRPM8 agonist cream in atopic dermatitis. Journal of the European Academy of Dermatology and Venereology. 2019;33(2):e67-e69. PMID 30067875