Supplements

Skullcap

Updated · 26 sources · Editorial policy

Skullcap usually means American skullcap (Scutellaria lateriflora), a North American plant in the mint family. Its dried leaves and stems are sold as teas, tinctures and capsules for anxiety, stress and insomnia, often mixed with other sedative herbs such as valerian (LiverTox: Skullcap).

It should not be confused with Chinese or Baikal skullcap (Scutellaria baicalensis), whose root is a traditional Chinese medicine and the main commercial source of the flavonoid baicalin. The two plants share some chemistry and are both linked to rare liver injury, but they are used for different purposes and have separate evidence bases. This page is about American skullcap and covers Chinese skullcap only where it matters for safety.

The single most important fact: human evidence for American skullcap is limited to three small trials, while LiverTox rates skullcap a “very likely but rare” cause of clinically apparent liver injury, with some cases traced to adulteration with germander. This page summarizes what the trials and the NIH LiverTox database report. It is for education only and is not medical advice.

Property Detail
Type Herbal supplement made from the aerial parts (leaves, stems, flowers) of Scutellaria lateriflora
Not the same as Chinese/Baikal skullcap (S. baicalensis), which uses the root
Other names Scullcap, helmet flower, hoodwort, mad weed, mad dog skullcap, Quaker bonnet, blue pimpernel
Main constituents Flavonoids, chiefly baicalin, baicalein, wogonin, scutellarin and lateriflorin; also GABA
Forms Tea powder, liquid tincture, capsules; often part of multi-herb sleep or stress blends
Doses used in trials 350 mg three times daily for 2 weeks; 400 mg/day of a 10%-baicalin extract for 8 weeks
Half-life Not established for the herb; baicalin half-life 4.2–10.8 h after oral baicalein in healthy adults
Liver safety (LiverTox) Likelihood score B: very likely but rare cause of clinically apparent liver injury
US status Sold over the counter as an herbal supplement; not an approved drug
WADA status Not named on the 2026 Prohibited List

What it is

Scutellaria is a large genus with hundreds of species. Several are used medicinally, and they differ in chemistry and potential toxicity (Cole et al., Planta Med 2008; LiverTox: Skullcap). The two that matter for supplements are:

Feature American skullcap Chinese/Baikal skullcap
Species Scutellaria lateriflora Scutellaria baicalensis (Huang Qin)
Part used Aerial parts (leaves, stems) Root
Traditional use Western herbal “nervine” for anxiety, sleeplessness and spasms Chinese medicine for inflammation, fever, cough, dysentery and high blood pressure
Typical products Sleep and stress teas, tinctures, capsules Joint supplements and medical foods (e.g. flavocoxid/Limbrel), Kampo and Chinese herbal formulas

Sources for the table: LiverTox: Skullcap, Lin et al., Phytochem Anal 2009, Gao et al., J Pharm Pharm Sci 2008, Li et al., J Ethnopharmacol 2014, LiverTox: Flavocoxid.

Native Americans used American skullcap for menstrual problems, nervousness, and digestive and kidney complaints. It was later used for “nervous disorders” such as hysteria, epilepsy and chorea, and today mainly as a sedative and sleep aid. The name refers to the flower’s resemblance to a soldier’s helmet (LiverTox: Skullcap).

Chemistry

The ethanol extract of American skullcap is dominated by flavonoids, mainly baicalin, lateriflorin, dihydrobaicalin and baicalein (Gafner et al., J AOAC Int 2003). One analysis measured baicalin at 40 mg/g in a 50% ethanol extract, baicalein at 33 mg/g in a 95% ethanol extract, and GABA at about 1.6 mg/g (Awad et al., Phytomedicine 2003). Wogonin and scutellarin have also been measured in the leaves and stems (Cole et al., Planta Med 2008).

Proposed mechanism

Baicalin and baicalein bind the benzodiazepine site of the GABA-A receptor, the receptor targeted by benzodiazepine drugs. This is the leading explanation for skullcap’s claimed calming effect (Awad et al., Phytomedicine 2003; LiverTox: Skullcap). The supporting data come from laboratory and animal work. In rats, an oral skullcap extract increased exploration of open areas in standard anxiety tests (Awad et al., Phytomedicine 2003). Whether ordinary oral doses produce this effect in people has not been shown.

How it works in the body

No human pharmacokinetic study of American skullcap itself has been published that we could find. What is known comes from purified baicalein and from Chinese skullcap root:

Study Population and dose Finding
Li et al., J Ethnopharmacol 2014 72 healthy adults; single oral baicalein doses of 100–2800 mg Baicalein peaked at 0.75–3.5 h; half-life 1.9–15.0 h. Its metabolite baicalin had a half-life of 4.2–10.8 h. Under 1% was cleared in urine; about 27% of baicalein left unchanged in feces
Lai et al., Biol Pharm Bull 2003 10 healthy men; 5.2 g Scutellariae Radix (Chinese skullcap root) powder Urinary baicalein was recovered as sulfate and glucuronide conjugates, totaling 7.2% of the dose

These data point to low urinary recovery and extensive conjugation of the skullcap flavones. They cannot be transferred directly to American skullcap teas or tinctures, whose flavonoid content varies widely (see Quality and contamination below).

What the research shows

Three small controlled trials have tested American skullcap in people. None enrolled patients with a diagnosed anxiety disorder.

Trial Design and n Dose and duration Main result
Wolfson & Hoffmann, Altern Ther Health Med 2003 Double-blind, placebo-controlled; 19 healthy volunteers Single doses: 350 mg freeze-dried herb, or 100 mg or 200 mg extract Authors reported anxiolytic effects; assessed with a non-validated scale
Brock et al., Phytother Res 2014 Randomized, double-blind, placebo-controlled crossover; 43 healthy adults 350 mg three times daily, 2 weeks per arm No difference vs placebo on anxiety (BAI, p = 0.191); mood score improved from baseline on skullcap
Di Minno et al., Nutrients 2025 Randomized, double-blind, placebo-controlled crossover; 66 adults with mild to moderate primary insomnia 400 mg/day extract standardized to 10% baicalin, 56 days per arm, 28-day washout Better self-rated sleep quality vs placebo; no adverse effects reported

Dose details for the 2003 study are from Tsuchiya, Molecules 2017.

Anxiety and mood

The first trial, by Wolfson and Hoffmann, gave single doses to 19 healthy volunteers and reported reduced anxiety. Reviewers have described its methods as weak and its results as poorly reported (Sarris et al., Evid Based Complement Alternat Med 2012). Its outcome measure was a non-validated, subjective scale (Lin et al., Phytochem Anal 2009).

The larger crossover trial in 43 healthy adults found no significant difference from placebo on the Beck Anxiety Inventory (p = 0.191). Total mood disturbance fell significantly from baseline during skullcap (p under 0.001) but not during placebo (p = 0.072). The authors noted that 81% of participants were at most mildly anxious, that baseline anxiety differed between groups, and that there was a carryover effect between periods (Brock et al., Phytother Res 2014). A within-group change from baseline is weaker evidence than a direct comparison with placebo.

Sleep

In the 2025 crossover trial, 66 adults with mild to moderate primary insomnia took a commercial extract (400 mg/day, standardized to 10% baicalin) or placebo for 56 days each (Di Minno et al., Nutrients 2025). Mean values from the paper:

Measure Placebo, start Placebo, day 56 Skullcap, start Skullcap, day 56
PSQI score (higher is worse) 11.5 13.3 13.0 9.5
Total sleep time (h) 5.4 5.0 5.0 6.2
Sleep efficiency (%) 75.7 73.8 71.3 80.3

The Pittsburgh Sleep Quality Index (PSQI) is a questionnaire scored 0–21. The treatment-by-time effect was significant (p under 0.001). Limitations named by the authors include self-reported outcomes and a carryover effect suggesting the 28-day washout was too short. Scores also worsened on placebo, and baseline values differed between periods. The supplement and placebo were supplied by the extract’s manufacturer. This is a single trial of one branded extract and has not been replicated.

Side effects and risks

The controlled trials reported few or no adverse effects, but they were small and short (Di Minno et al., Nutrients 2025). The main documented risk is liver injury, mostly from case reports.

Liver injury with American skullcap

LiverTox, the NIH database on drug-induced liver injury, gives skullcap a likelihood score of B: “very likely but rare” cause of clinically apparent liver injury (LiverTox: Skullcap). Its summary:

  • Confounding. In most cases several herbs were taken together, so skullcap’s role was unclear. Common co-ingredients were valerian, mistletoe, comfrey, chaparral and pau d’arco.
  • Timing and pattern. Jaundice began 1–12 weeks after starting the product. Enzyme rises were typically hepatocellular (liver-cell injury rather than bile-flow blockage).
  • Course. Most patients recovered quickly after stopping, but at least one case progressed to acute liver failure. No chronic liver disease or cirrhosis has been linked to skullcap.
  • Mechanism. Unknown.

Selected published cases:

Report Products Outcome
MacGregor et al., BMJ 1989 Four women aged 41–57 using UK stress remedies believed to contain skullcap and/or valerian Jaundice 2–8 weeks after starting; resolved 2–19 months after stopping
Hullar et al., Am J Med 1999 28-year-old man taking skullcap and pau d’arco for 6 months Liver failure, transplant, death; explant showed sinusoidal obstruction syndrome
Estes et al., Arch Surg 2003 20 patients referred for fulminant liver failure in Oregon, 2001–2002 10 used potentially hepatotoxic supplements; LiverTox lists one as skullcap
LiverTox case 1 53-year-old woman taking a skullcap and valerian sleep aid Jaundice at 4 weeks (ALT 1208 U/L); liver tests normal 3 months after stopping

LiverTox also notes that a 2014 reanalysis scored the reported re-exposure in two skullcap cases as negative, and that large US and European liver-injury registries have not specifically attributed cases to American skullcap (LiverTox: Skullcap).

Germander adulteration

Some suspected skullcap cases may have been caused by a different plant. LiverTox states that phytochemical analysis has found germander or mislabeling in some cases of suspected skullcap liver injury (LiverTox: Skullcap). American skullcap has been adulterated with the germanders Teucrium canadense and Teucrium chamaedrys. Laboratory methods have been developed to tell them apart (Gafner et al., J AOAC Int 2003; Lin et al., Phytochem Anal 2009).

Germander is a well-established liver toxin, rated likelihood score A by LiverTox (LiverTox: Germander):

  • Toxins. Furan-containing diterpenoids such as teucrin A are oxidized by liver cytochrome P450 enzymes into reactive metabolites. American skullcap’s own diterpenes have a different ring structure (Lin et al., Phytochem Anal 2009).
  • French outbreak. In France, where germander was sold as a drug or tea to aid weight loss, 26 cases of acute hepatitis were reported to pharmacovigilance centers. Re-exposure caused prompt recurrence in 12 cases, and the French Ministry of Health prohibited all germander-containing medicinal products (Castot & Larrey, Gastroenterol Clin Biol 1992).
  • Clinical picture. Hepatitis appeared 3–18 weeks after starting germander, with full recovery in 1.5–6 months after stopping in a 7-patient series (Larrey et al., Ann Intern Med 1992). Acute liver failure, death and chronic hepatitis have also been reported (LiverTox: Germander).

Liver injury with Chinese skullcap (baicalin products)

LiverTox notes several reports and small case series of acute liver injury with jaundice 1–3 months after starting products containing Chinese skullcap, resembling the injury seen with American skullcap (LiverTox: Skullcap). Several involved joint products that combine Chinese skullcap with black catechu (Acacia catechu):

  • Move Free Advanced. Two patients developed liver injury that resolved after stopping; the authors judged Chinese skullcap the most likely cause (Linnebur et al., Pharmacotherapy 2010). Another case had jaundice plus lung infiltrates (Dhanasekaran et al., Case Reports Hepatol 2013).
  • Rechallenge case. A 78-year-old woman developed jaundice (ALT 1626 U/L) on a Chinese skullcap mixture; it resolved on stopping and recurred within 2 weeks of restarting (Yang et al., World J Hepatol 2012).
  • Flavocoxid (Limbrel). This prescription medical food of baicalin and catechins was linked to four cases of acute liver injury in women aged 57–68 (Chalasani et al., Ann Intern Med 2012). In premarketing trials, aminotransferase rises occurred in up to 10% of users, and over 3 times the upper limit in 1–2%. Its status as an FDA medical food was withdrawn in December 2017 (LiverTox: Flavocoxid).

By contrast, single oral doses of purified baicalein up to 2800 mg showed no liver or kidney toxicity in a 72-person phase 1 trial (Li et al., J Ethnopharmacol 2014). Which component of these products harms the liver, and why, is unknown.

Interactions and who should be cautious

We found no formal human drug-interaction studies for American skullcap. Because it is marketed as a sedative and is often combined with other herbs, the reported liver cases usually involved several products at once (LiverTox: Skullcap). LiverTox advises against re-exposure after germander-related liver injury (LiverTox: Germander).

Quality and contamination

Product content varies widely. In 11 commercial tinctures, baicalin ranged from 0 to 12.66 mg/mL in the seven American skullcap tinctures, so at least one contained no detectable baicalin (Gao et al., J Pharm Pharm Sci 2008).

Several laboratory methods can detect germander in skullcap:

These methods exist, but buyers cannot verify which, if any, a given manufacturer uses.

Skullcap is sold over the counter as an herbal supplement and appears in many multi-ingredient herbal mixtures (LiverTox: Skullcap). It is not an approved drug for any condition. Neither skullcap nor its flavonoids are named on the WADA 2026 Prohibited List.

Key takeaways

  • Two different plants share the name. American skullcap (S. lateriflora, leaves and stems) is the sleep and anxiety herb; Chinese skullcap (S. baicalensis, root) is the baicalin source used in joint products and Chinese medicine.
  • Human evidence is thin. Three small trials in people without anxiety disorders: one showed no anxiety benefit over placebo, and one manufacturer-supplied extract improved self-rated sleep in 66 adults.
  • Mechanism is plausible but unproven in people. Baicalin and baicalein bind the GABA-A benzodiazepine site in laboratory studies.
  • Rare but serious liver injury. LiverTox rates skullcap a “very likely but rare” cause, including at least one case of liver failure. Most cases involved multi-herb products.
  • Germander adulteration is a documented hazard. Some suspected skullcap cases were linked to germander, an established liver toxin whose medicinal products were banned in France.
  • Product quality is inconsistent. Commercial tinctures range from substantial to undetectable flavonoid content.

Sources

  1. National Institute of Diabetes and Digestive and Kidney Diseases. LiverTox: Skullcap. Updated March 28, 2020. NCBI Bookshelf.
  2. National Institute of Diabetes and Digestive and Kidney Diseases. LiverTox: Germander. Updated March 12, 2018. NCBI Bookshelf.
  3. National Institute of Diabetes and Digestive and Kidney Diseases. LiverTox: Flavocoxid. Updated January 30, 2018. NCBI Bookshelf.
  4. Wolfson P, Hoffmann DL. An investigation into the efficacy of Scutellaria lateriflora in healthy volunteers. Altern Ther Health Med. 2003;9(2):74–78. PubMed.
  5. Brock C, Whitehouse J, Tewfik I, Towell T. American Skullcap (Scutellaria lateriflora): a randomised, double-blind placebo-controlled crossover study of its effects on mood in healthy volunteers. Phytother Res. 2014;28(5):692–698. PubMed.
  6. Di Minno A, Morone MV, Buccato DG, et al. Efficacy and tolerability of a chemically characterized Scutellaria lateriflora L. extract-based food supplement for sleep management: a single-center, controlled, randomized, crossover, double-blind clinical trial. Nutrients. 2025;17(9):1491. PubMed.
  7. Sarris J, Moylan S, Camfield DA, et al. Complementary medicine, exercise, meditation, diet, and lifestyle modification for anxiety disorders: a review of current evidence. Evid Based Complement Alternat Med. 2012;2012:809653. PubMed.
  8. Tsuchiya H. Anesthetic agents of plant origin: a review of phytochemicals with anesthetic activity. Molecules. 2017;22(8):1369. PubMed.
  9. Awad R, Arnason JT, Trudeau V, et al. Phytochemical and biological analysis of skullcap (Scutellaria lateriflora L.): a medicinal plant with anxiolytic properties. Phytomedicine. 2003;10(8):640–649. PubMed.
  10. Cole IB, Cao J, Alan AR, et al. Comparisons of Scutellaria baicalensis, Scutellaria lateriflora and Scutellaria racemosa: genome size, antioxidant potential and phytochemistry. Planta Med. 2008;74(4):474–481. PubMed.
  11. Gafner S, Bergeron C, Batcha LL, et al. Analysis of Scutellaria lateriflora and its adulterants Teucrium canadense and Teucrium chamaedrys by LC-UV/MS, TLC, and digital photomicroscopy. J AOAC Int. 2003;86(3):453–460. PubMed.
  12. Lin LZ, Harnly JM, Upton R. Comparison of the phenolic component profiles of skullcap (Scutellaria lateriflora) and germander (Teucrium canadense and T. chamaedrys), a potentially hepatotoxic adulterant. Phytochem Anal. 2009;20(4):298–306. PubMed.
  13. Gao J, Sanchez-Medina A, Pendry BA, et al. Validation of a HPLC method for flavonoid biomarkers in skullcap (Scutellaria) and its use to illustrate wide variability in the quality of commercial tinctures. J Pharm Pharm Sci. 2008;11(1):77–87. PubMed.
  14. Sandasi M, Vermaak I, Chen W, Viljoen AM. Skullcap and germander: preventing potential toxicity through the application of hyperspectral imaging and multivariate image analysis as a novel quality control method. Planta Med. 2014;80(15):1329–1339. PubMed.
  15. Li M, Shi A, Pang H, et al. Safety, tolerability, and pharmacokinetics of a single ascending dose of baicalein chewable tablets in healthy subjects. J Ethnopharmacol. 2014;156:210–215. PubMed.
  16. Lai MY, Hsiu SL, Chen CC, et al. Urinary pharmacokinetics of baicalein, wogonin and their glycosides after oral administration of Scutellariae Radix in humans. Biol Pharm Bull. 2003;26(1):79–83. PubMed.
  17. MacGregor FB, Abernethy VE, Dahabra S, et al. Hepatotoxicity of herbal remedies. BMJ. 1989;299(6708):1156–1157. PubMed.
  18. Hullar TE, Sapers BL, Ridker PM, et al. Herbal toxicity and fatal hepatic failure. Am J Med. 1999;106(2):267–268. PubMed.
  19. Estes JD, Stolpman D, Olyaei A, et al. High prevalence of potentially hepatotoxic herbal supplement use in patients with fulminant hepatic failure. Arch Surg. 2003;138(8):852–858. PubMed.
  20. Larrey D, Vial T, Pauwels A, et al. Hepatitis after germander (Teucrium chamaedrys) administration: another instance of herbal medicine hepatotoxicity. Ann Intern Med. 1992;117(2):129–132. PubMed.
  21. Castot A, Larrey D. Hepatitis observed during a treatment with a drug or tea containing Wild Germander. Evaluation of 26 cases reported to the Regional Centers of Pharmacovigilance [in French]. Gastroenterol Clin Biol. 1992;16(12):916–922. PubMed.
  22. Linnebur SA, Rapacchietta OC, Vejar M. Hepatotoxicity associated with Chinese skullcap contained in Move Free Advanced dietary supplement: two case reports and review of the literature. Pharmacotherapy. 2010;30(7):750, 258e–262e. PubMed.
  23. Yang L, Aronsohn A, Hart J, Jensen D. Herbal hepatoxicity from Chinese skullcap: a case report. World J Hepatol. 2012;4(7):231–233. PubMed.
  24. Dhanasekaran R, Owens V, Sanchez W. Chinese skullcap in move free arthritis supplement causes drug induced liver injury and pulmonary infiltrates. Case Reports Hepatol. 2013;2013:965092. PubMed.
  25. Chalasani N, Vuppalanchi R, Navarro V, et al. Acute liver injury due to flavocoxid (Limbrel), a medical food for osteoarthritis: a case series. Ann Intern Med. 2012;156(12):857–860, W297–W300. PubMed.
  26. World Anti-Doping Agency. World Anti-Doping Code International Standard: Prohibited List 2026. WADA 2026 Prohibited List.