Prunella Vulgaris (Self-Heal)
A mint-family herb used in Chinese medicine for thyroid nodules and, in the West, for herpes. The thyroid trials are small and low quality, and the antiviral work is entirely in cells and animals.
Evidence last reviewed: August 2026
What the science says
- Thyroid nodules Limited evidence
A meta-analysis of Chinese randomized trials reported that Prunella preparations added to standard care reduced thyroid nodule size. The included trials were small, poorly blinded and at high risk of bias, so the effect size is unreliable.
- Herpes simplex virus Limited evidence
Polysaccharide and lignin-carbohydrate fractions from Prunella block herpes simplex virus in cell culture and in animal models. No human trial has tested it for cold sores or genital herpes.
Dosage & safety
Studied doseChinese trials used decoctions of roughly 15–30 g of dried spike per day. Western capsules typically supply 500 mg of extract once or twice daily, a dose that has not been studied.
SafetyLittle modern safety data exists. It may affect thyroid function and blood pressure, so people with thyroid disease, those on levothyroxine or antihypertensives, and pregnant women should avoid it without supervision.
Scientific references
- Safety and efficacy of Prunella vulgaris preparation in adjuvant treatment of thyroid nodules: A meta-analysis
- Prunella vulgaris polysaccharide inhibits herpes simplex virus infection by blocking TLR-mediated NF-κB activation
- Chemical properties, mode of action, and in vivo anti-herpes activities of a lignin-carbohydrate complex from Prunella vulgaris
Where to buy
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