Yarrow (Achillea millefolium) has a long history of traditional use for supporting the circulatory system, including capillaries. Historically, yarrow has been employed in European, Native American, and Chinese herbal medicine to aid wound healing, stop bleeding, and promote blood vessel health. The plant's astringent properties were believed to help strengthen blood vessels, including capillaries, and reduce minor bleeding or bruising. Yarrow contains flavonoids and other phytochemicals that have been suggested to contribute to these effects.

However, scientific studies specifically examining yarrow's effects on capillary strength or capillary health in humans are limited. Some in vitro and animal studies suggest anti-inflammatory and vasoprotective properties, but direct evidence in humans is lacking. The use of yarrow for capillary support is therefore primarily justified by traditional medicine rather than robust scientific validation. Its traditional application persists in modern herbal practices, especially for minor wounds and circulatory support, but with only modest scientific support for its efficacy in capillary health.