Licorice root extract offers several potential benefits for the scalp, primarily through anti-inflammatory effects, antimicrobial properties, and possible hair growth promotion via specific bioactive compounds. The anti-inflammatory compound licochalcone A, found in Glycyrrhiza inflata root extract, significantly reduces scalp microinflammation and alleviates symptoms of dry, itchy scalp when applied topically.

[1] In a randomized half-head study of 30 subjects with dry and itchy scalp conditions, a tonic containing licorice root extract (along with urea, lactate, and polidocanol) significantly increased scalp moisture, reduced itching and tautness, and decreased pro-inflammatory markers after 4 weeks of application.

[1] 18-β-glycyrrhetinic acid, a major component of licorice, may promote hair growth through multiple mechanisms.

[2] This compound stimulates proliferation of both dermal papilla cells and outer root sheath cells from human hair follicles, inhibits 5α-reductase activity (IC50 of 137.1 µM), and suppresses transforming growth factor-β1 (TGF-β1) expression, potentially prolonging the anagen phase of the hair cycle.

[2] These properties suggest potential efficacy for androgenetic alopecia, though clinical evidence in humans remains limited. Licorice extracts also demonstrate antioxidant and antimicrobial properties that may benefit overall scalp health.[3][4][5] The general pharmacological effects include anti-inflammatory, antioxidative, anti-allergenic, and antimicrobial activities.

[3] However, it's important to note that most evidence for hair growth promotion comes from in vitro and animal studies, with limited clinical trial data specifically for scalp applications.

References

1. Efficacy of a New Tonic Containing Urea, Lactate, Polidocanol, and Glycyrrhiza Inflata Root Extract in the Treatment of a Dry, Itchy, and Subclinically Inflamed Scalp. Schweiger D, Baufeld C, Drescher P, et al. Skin Pharmacology and Physiology. 2013;26(2):108-18. doi:10.1159/000348473.

2. 18-Β-Glycyrrhetinic Acid Promotes Hair Growth by Stimulating the Proliferation of Dermal Papilla Cells and Outer Root Sheath Cells, and Extends the Anagen Phase by Inhibiting 5α-Reductase. Hagiwara K, Kiso A, Ono S, et al. Biological & Pharmaceutical Bulletin. 2024;47(7):1392-1395. doi:10.1248/bpb.b24-00302.

3. A Review of the Pharmacological Efficacy and Safety of Licorice Root From Corroborative Clinical Trial Findings. Kwon YJ, Son DH, Chung TH, Lee YJ. Journal of Medicinal Food. 2020;23(1):12-20. doi:10.1089/jmf.2019.4459.

4. Phytochemistry, Pharmacological Activity, and Potential Health Benefits of . Hasan MK, Ara I, Mondal MSA, Kabir Y. Heliyon. 2021;7(6):e07240. doi:10.1016/j.heliyon.2021.e07240.

5. Pharmacological Effects of Glycyrrhiza Spp. And Its Bioactive Constituents: Update and Review. Hosseinzadeh H, Nassiri-Asl M. Phytotherapy Research : PTR. 2015;29(12):1868-86. doi:10.1002/ptr.5487.

6. Can Plant Extracts Help Prevent Hair Loss or Promote Hair Growth? A Review Comparing Their Therapeutic Efficacies, Phytochemical Components, and Modulatory Targets. Choi JY, Boo MY, Boo YC. Molecules (Basel, Switzerland). 2024;29(10):2288. doi:10.3390/molecules29102288.

Saw palmetto (Serenoa repens) may stabilize hair loss in androgenetic alopecia (AGA) through 5α-reductase inhibition, though its efficacy appears less than finasteride. The extract also demonstrates additional hair growth-promoting mechanisms beyond androgen modulation. The primary mechanism involves inhibition of 5α-reductase type II, which converts testosterone to dihydrotestosterone (DHT), a key mediator of AGA.[1] A proprietary lipidosterolic extract demonstrated potent 5α-reductase inhibition with an IC50 of 0.39 μg/mL, more effective than standard saw palmetto extracts.

[2] The active fatty acids (lauric, oleic, myristic, and linoleic acids) contribute to this inhibitory activity with IC50 values of 42.1 to 67.6 μg/mL.

[3] Clinical evidence shows modest benefit. An RCT in 19 males with mild-to-moderate AGA showed 60% investigator-assessed improvement versus 11% with placebo after 5 months, though this difference was not statistically significant.

[1] A comparative trial in 100 men found finasteride more effective at improving hair loss, while saw palmetto stabilized hair loss after 24 months.

[1] Beyond 5α-reductase inhibition, saw palmetto exhibits 5α-reductase-independent mechanisms including prolongation of the anagen phase, enhanced hair follicle stem cell niche reinforcement, and activation of TGF-β and mitochondrial signaling pathways.

[2][4] These effects include increased dermal papilla cell proliferation and reduced apoptosis.[4][5] Adverse effects are generally mild (nausea, diarrhea, constipation), though sexual dysfunction can occur to a lesser extent than with finasteride.

[1] Physicians should note the theoretical risk of masking early prostate cancer detection due to 5α-reductase inhibition.

References

1. Evaluation of the Safety and Effectiveness of Nutritional Supplements for Treating Hair Loss: A Systematic Review. Drake L, Reyes-Hadsall S, Martinez J, et al. JAMA Dermatology. 2023;159(1):79-86. doi:10.1001/jamadermatol.2022.4867.

2. A Proprietary Lipidosterolic Extract of Serenoa Repens Promotes Hair Growth Through Mechanisms That Extend Beyond 5-Alpha Reductase Inhibition: Insights From Human Hair Follicle Organ Culture. Broadley D, Le Riche A, Guénin S, et al. International Journal of Cosmetic Science. 2025;. doi:10.1111/ics.70035.

3. Pharmacologically Relevant Receptor Binding Characteristics and 5alpha-Reductase Inhibitory Activity of Free Fatty Acids Contained in Saw Palmetto Extract. Abe M, Ito Y, Oyunzul L, Oki-Fujino T, Yamada S. Biological & Pharmaceutical Bulletin. 2009;32(4):646-50. doi:10.1248/bpb.32.646.

4. Serenoa Repens Extracts Promote Hair Regeneration and Repair of Hair Loss Mouse Models by Activating TGF-β and Mitochondrial Signaling Pathway. Zhu HL, Gao YH, Yang JQ, Li JB, Gao J. European Review for Medical and Pharmacological Sciences. 2018;22(12):4000-4008. doi:10.26355/eurrev_201806_15285.

5. Can Plant Extracts Help Prevent Hair Loss or Promote Hair Growth? A Review Comparing Their Therapeutic Efficacies, Phytochemical Components, and Modulatory Targets. Choi JY, Boo MY, Boo YC. Molecules (Basel, Switzerland). 2024;29(10):2288. doi:10.3390/molecules29102288.

Topical green tea extract, primarily through its active component epigallocatechin-3-gallate (EGCG), promotes hair growth, reduces inflammation, and provides antioxidant protection for the scalp. The hair growth-promoting effects occur through dual proliferative and anti-apoptotic mechanisms on dermal papilla cells (DPCs). EGCG stimulates DPC proliferation by upregulating phosphorylated ERK and AKT pathways while increasing the Bcl-2/Bax ratio to reduce apoptosis.

[1] In a mouse model of testosterone-induced hair loss, topical EGCG significantly reduced hair loss and diminished apoptosis of follicular epithelial cells, though this effect appeared independent of the androgen metabolic pathway.

[2] EGCG also demonstrates 5α-reductase inhibitory activity, suggesting potential utility in androgenetic alopecia.

[1] Beyond hair growth, green tea extracts exhibit anti-inflammatory properties beneficial for inflammatory scalp conditions. In psoriasis models, tea extracts reduced expression of IL-17 and TNF-α cytokines and ameliorated skin damage.[3] The anti-inflammatory effects are mediated through modulation of inflammatory signaling pathways and reduction of oxidative stress markers.

[4] Antioxidant and photoprotective properties help neutralize free radicals generated by UV radiation and environmental stressors, potentially preventing premature aging and cellular damage to the scalp.

[5][6] Green tea extracts also demonstrate antimicrobial effects and can modulate immune cell function related to skin microorganisms through dendritic cell signaling.

[4] For sebum regulation, topical green tea polyphenols may reduce sebum production, which could benefit scalp conditions associated with excess sebum.

[7] The stability of EGCG formulations depends on concentration, pH, and temperature, with higher concentrations and lower pH values generally providing better stability.

References

1. Human Hair Growth Enhancement in Vitro by Green Tea Epigallocatechin-3-Gallate (EGCG). Kwon OS, Han JH, Yoo HG, et al. Phytomedicine : International Journal of Phytotherapy and Phytopharmacology. 2007;14(7-8):551-5. doi:10.1016/j.phymed.2006.09.009.

2. Effects of Topical Application of EGCG on Testosterone-Induced Hair Loss in a Mouse Model. Kim YY, Up No S, Kim MH, et al. Experimental Dermatology. 2011;20(12):1015-7. doi:10.1111/j.1600-0625.2011.01353.x.

3. Anti-Psoriatic Activity of Black, Green and White Tea Extracts From Southeastern China. Zhang L, Huang Z, Xuan J, et al. Molecules (Basel, Switzerland). 2024;29(6):1279. doi:10.3390/molecules29061279.

4. Pleiotropic Effects of a Camellia Sinensis Leaf Extract on In vitro and In vivo Skin Health Characteristics. Shill DD, Stade HN, Goodson KC, et al. International Journal of Cosmetic Science. 2025;. doi:10.1111/ics.13073.

5. Epigallocatechin-Gallate (EGCG): An Essential Molecule for Human Health and Well-Being. Rovaldi E, Di Donato V, Paolino G, et al. International Journal of Molecular Sciences. 2025;26(18):9253. doi:10.3390/ijms26189253.

6. Green Tea Catechins and Skin Health. Zheng XQ, Zhang XH, Gao HQ, et al. Antioxidants (Basel, Switzerland). 2024;13(12):1506. doi:10.3390/antiox13121506.

7. Green Tea and Other Tea Polyphenols: Effects on Sebum Production and Acne Vulgaris. Saric S, Notay M, Sivamani RK. Antioxidants (Basel, Switzerland). 2016;6(1):E2. doi:10.3390/antiox6010002.

8. Great Green Tea Ingredient? A Narrative Literature Review on Epigallocatechin Gallate and Its Biophysical Properties for Topical Use in Dermatology. Frasheri L, Schielein MC, Tizek L, et al. Phytotherapy Research : PTR. 2020;34(9):2170-2179. doi:10.1002/ptr.6670.

Topical Spilanthes extract (Spilanthes acmella) offers potential scalp benefits through anti-inflammatory effects, hair growth promotion, and antioxidant properties, primarily mediated by its bioactive compound spilanthol. The anti-inflammatory effects are well-documented across multiple pathways. Spilanthol inhibits NF-κB and MAPK signaling pathways, reducing expression of inflammatory mediators including iNOS, COX-2, IL-6, IL-8, and TNF-α.

[1][2][3][4] In keratinocytes, spilanthol suppresses TNF-α-induced ICAM-1 expression and enhances heme oxygenase-1 (HO-1) expression while inhibiting JNK phosphorylation.[3] Topical application ameliorated allergic inflammation in DNCB-induced atopic dermatitis models, reducing epidermal thickness, mast cell infiltration, and serum IgE levels.

[5] For hair growth promotion, Spilanthes extract demonstrated significant effects on dermal papilla cells. The extract increased hDPC proliferation by 123-132% at concentrations of 15.6-31.3 μg/mL.[6] Mechanistically, it activated Wnt/β-catenin signaling, increased hepatocyte growth factor expression, decreased TGF-β1 and SMAD2/3 levels, and enhanced the Bcl-2/Bax ratio while activating ERK and Akt pathways.

[6] In male C57BL/6 mice, topical application induced anagen phase and significantly enhanced hair growth over 21 days.[6] Additionally, Spilanthes lipid extracts protected against oxidative stress-induced alopecia by reducing ROS levels by 90.7%, inhibiting ferroptosis pathways, and promoting antioxidant gene expression (1.55-3.52 times increase).

[7] In vivo application increased new hair length by 16.7% and new hair follicle length by 92.6%.[7] The extract also possesses antimicrobial properties against various organisms including Corynebacterium diphtheriae and Bacillus subtilis, potentially beneficial for scalp microbiome balance.

References

1. Anti-Inflammatory Effect of Spilanthol From Spilanthes Acmella on Murine Macrophage by Down-Regulating LPS-induced Inflammatory Mediators. Wu LC, Fan NC, Lin MH, et al. Journal of Agricultural and Food Chemistry. 2008;56(7):2341-9. doi:10.1021/jf073057e.

2. Spilanthol Inhibits Inflammatory Transcription Factors and iNOS Expression in Macrophages and Exerts Anti-Inflammatory Effects in Dermatitis and Pancreatitis. Bakondi E, Singh SB, Hajnády Z, et al. International Journal of Molecular Sciences. 2019;20(17):E4308. doi:10.3390/ijms20174308.

3. Spilanthol Inhibits TNF‑α‑induced ICAM‑1 Expression and Pro‑inflammatory Responses by Inducing Heme Oxygenase‑1 Expression and Suppressing pJNK in HaCaT Keratinocytes. Huang CH, Chang LC, Hu S, Hsiao CY, Wu SJ. Molecular Medicine Reports. 2018;18(3):2987-2994. doi:10.3892/mmr.2018.9245.

4. Spilanthes acmella Inhibits Inflammatory Responses via Inhibition of NF-κB and MAPK Signaling Pathways in RAW 264.7 Macrophages. Cho YC, Bach TT, Kim BR, Vuong HL, Cho S. Molecular Medicine Reports. 2017;16(1):339-346. doi:10.3892/mmr.2017.6555.

5. Topical Spilanthol Inhibits MAPK Signaling and Ameliorates Allergic Inflammation in DNCB-Induced Atopic Dermatitis in Mice. Huang WC, Huang CH, Hu S, Peng HL, Wu SJ. International Journal of Molecular Sciences. 2019;20(10):E2490. doi:10.3390/ijms20102490.

6. Hair Growth Potential of Extract and Its Associated Mechanisms. Jin GR, Zhang YL, Yap J, Boisvert WA, Lee BH. Pharmaceutical Biology. 2020;58(1):400-409. doi:10.1080/13880209.2020.1759654.

7. Sp. Extracted Lipids Prevent Alopecia by Enhancing Antioxidation and Inhibiting Ferroptosis of Dermal Papilla Cells. Zeng Z, Wang B, Ibrar M, et al. Antioxidants (Basel, Switzerland). 2023;12(7):1332. doi:10.3390/antiox12071332.

8. Bioactive Metabolites From Spilanthes Acmella Murr. Prachayasittikul S, Suphapong S, Worachartcheewan A, et al. Molecules (Basel, Switzerland). 2009;14(2):850-67. doi:10.3390/molecules14020850.

Lobelia extract demonstrates potential scalp benefits through anti-inflammatory, antioxidant, antimicrobial, and wound-healing properties, though most evidence comes from preclinical studies rather than specific scalp applications. The anti-inflammatory effects are well-documented across multiple Lobelia species. Lobelia chinensis extract inhibits pro-inflammatory mediators including iNOS, COX-2, TNF-α, IL-6, and IL-1β through suppression of the NF-κB pathway.

[1][2] In LPS-stimulated macrophages and keratinocytes, the extract significantly reduced nitric oxide production, ROS generation, and inflammatory cytokine expression.

[1] Lobelia laxiflora alkaloids also demonstrated anti-inflammatory activity by inhibiting complement activation, particularly via the classical pathway.

[3] Antioxidant properties provide protection against oxidative stress, a key factor in scalp inflammation and premature aging. Lobelia chinensis extracts showed significant free radical scavenging activity, while the essential oil and extracts demonstrated both anti- and prooxidant properties depending on concentration.

[2][4] For wound healing and tissue repair, Lobelia alsinoides topical ointment (10% w/w) significantly accelerated wound contraction (99.33% by day 16), shortened epithelialization time, enhanced collagen deposition, and promoted angiogenesis in rat models.

[5][6] The formulation outperformed silver sulfadiazine in burn wound healing, demonstrating increased fibroblast growth and improved extracellular matrix remodeling.

[6] Antimicrobial activity against both Gram-positive and Gram-negative bacteria has been reported, potentially beneficial for scalp microbiome balance and conditions like dandruff, though Lobelia was not specifically mentioned among anti-dandruff botanicals in comprehensive reviews.

[4][7] The phytochemical profile includes piperidine alkaloids (lobeline, lobinaline), phenolic compounds (caffeic acid, rosmarinic acid, luteolin derivatives), terpenoids, and tannins.

[4][8][9] Clinical studies in humans are needed to confirm these effects for scalp-specific applications.

References

1. Anti-Inflammatory and Antioxidant Properties of L. Extracts and : Potential Application for Skin Care. He BW, Wang FF, Qu LP. Evidence-Based Complementary and Alternative Medicine : eCAM. 2022;2022:7579572. doi:10.1155/2022/7579572.

2. Anti-Oxidative and Anti-Inflammatory Effects of Lobelia Chinensis in Vitro and in Vivo. Li KC, Ho YL, Huang GJ, Chang YS. The American Journal of Chinese Medicine. 2015;43(2):269-87. doi:10.1142/S0192415X15500184.

3. Phytochemical Study and Antiinflammatory Properties of Lobelia Laxiflora L. Philipov S, Istatkova R, Ivanovska N, et al. Zeitschrift Fur Naturforschung. C, Journal of Biosciences. 1998 May-Jun;53(5-6):311-7. doi:10.1515/znc-1998-5-603.

4. : Essential Oil and Extracts, Their Biological Activities, and Perspectives on the Development of New Medicinal and Cosmetic Products. Hudz N, Kobylinska L, Pokajewicz K, et al. Molecules (Basel, Switzerland). 2023;28(21):7444. doi:10.3390/molecules28217444.

5. Accelerated Full-Thickness Wound Healing by a Topical Ointment Formulated With Lobelia Alsinoides Lam. Ethanolic Extract. Samdavid Thanapaul RJR, Manikandan SK, Paulraj MS, Nadar MSAM. International Journal of Molecular Sciences. 2025;26(21):10663. doi:10.3390/ijms262110663.

6. Efficacy of Lobelia Alsinoides Lam Ethanolic Extract on a Third-Degree Burn: An Experimental Study on Rats. Samdavid Thanapaul RJR, Ranjan A, Manikandan SK, Nadar MSAM. Dermatologic Therapy. 2020;33(6):e14242. doi:10.1111/dth.14242.

7. Promising Essential Oils/Plant Extracts in the Prevention and Treatment of Dandruff Pathogenesis. Kumari KMU, Yadav NP, Luqman S. Current Topics in Medicinal Chemistry. 2022;22(13):1104-1133. doi:10.2174/1568026622666220531120226.

8. Novel Multifunctional Pharmacology of Lobinaline, the Major Alkaloid From Lobelia Cardinalis. Brown DP, Rogers DT, Pomerleau F, et al. Fitoterapia. 2016;111:109-23. doi:10.1016/j.fitote.2016.04.013.

9. HPLC-ESI-MS/MS of Brain Neurotransmitter Modulator Lobeline and Related Piperidine Alkaloids in Lobelia Inflata L. Kursinszki L, Szőke É. Journal of Mass Spectrometry : JMS. 2015;50(5):727-33. doi:10.1002/jms.3581.