Synopsis

Source of validity: Traditional
Rating (out of 5): 2

Knotweed, particularly Polygonum cuspidatum (Japanese knotweed), has a long history of use in traditional medicine systems, especially in East Asia. Its use for skin conditions, including psoriasis, is based primarily on traditional knowledge rather than robust scientific validation. In Traditional Chinese Medicine (TCM), knotweed is believed to "clear heat" and "remove toxins," which are concepts associated with inflammatory skin diseases such as psoriasis. Practitioners have historically prescribed extracts or decoctions of knotweed for various skin eruptions, itching, and redness.

From a modern scientific perspective, knotweed contains several bioactive compounds, most notably resveratrol and polydatin, which are known for their anti-inflammatory and antioxidant properties. Some laboratory studies suggest that these compounds may modulate inflammatory pathways relevant to psoriasis, such as reducing pro-inflammatory cytokines (e.g., TNF-α, IL-6). However, there are very few clinical studies directly evaluating knotweed or its extracts in the treatment of psoriasis in humans. Most available evidence comes from animal models or in vitro studies, which, while promising, are insufficient for strong clinical recommendations.

In summary, the use of knotweed for psoriasis is primarily grounded in traditional medicine, with limited scientific support. While its bioactive constituents have mechanisms that plausibly could benefit psoriasis, high-quality human trials are lacking. Therefore, its evidence rating is modest, and its use should be considered complementary rather than primary therapy.

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