Supplement analysis backed by scientific evidence · PT

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Limited evidenceImmunity

Yin Qiao San

A classical Chinese formula built on honeysuckle and forsythia, taken at the first sign of a cold. One placebo-controlled trial is positive but was stopped early and badly underpowered.

Evidence last reviewed: August 2026

What the science says

  • Common cold symptoms Limited evidence

    A randomised, placebo-controlled, multicentre trial in Korea (where the formula is called Eunkyosan) found better symptom and quality-of-life scores on the WURSS-21 than placebo. It enrolled only 128 of a planned 375 participants before being terminated because of the COVID-19 pandemic, and the authors themselves call for a definitive full-scale study.

  • Quality of the wider trial base Limited evidence

    A PRISMA-compliant systematic review of randomised trials of the formula for the common cold found few studies, small samples and methodological weaknesses that prevented firm conclusions.

  • Antiviral mechanism Limited evidence

    Laboratory work reports antiviral and anti-inflammatory actions for constituents such as wogonin in cell and animal models. This explains plausibility but says nothing about clinical benefit.

Dosage & safety

Studied doseTraditional decoction or granules taken three times daily at the onset of symptoms; the Korean trial used a standardised granule preparation three times daily for up to eight days. Product strengths vary widely.
SafetyGenerally well tolerated over short courses, with no serious adverse events in the trial. Chinese patent medicines are variably regulated and have been found adulterated with pharmaceuticals or contaminated with heavy metals, so brand matters. Avoid in pregnancy without professional advice. Not a substitute for medical care if symptoms are severe or persist beyond about ten days.

Scientific references

Where to buy

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