Polygonum species, including Polygonum cuspidatum (Japanese knotweed), Polygonum aviculare (common knotgrass), and Polygonum multiflorum (He Shou Wu or Fo-ti), have a long history of use in traditional medicine systems such as Traditional Chinese Medicine (TCM). In this context, some Polygonum species are employed topically or internally to address skin ailments, including itching (pruritus), rashes, and eczema. The traditional rationale often involves concepts such as "clearing heat," "detoxifying," or "dispelling wind," which are believed to be underlying factors in skin discomfort and itching.

However, while there are scattered ethnobotanical reports and some inclusion in TCM materia medica, scientific studies directly evaluating Polygonum spp. for anti-pruritic (anti-itch) effects in humans are lacking. Some laboratory research indicates that Polygonum extracts possess anti-inflammatory, antioxidant, or antimicrobial properties, which could in theory help with skin irritation or conditions associated with itching. Still, clinical evidence in support of their use specifically for itching is minimal or absent. Thus, the use of unspecified Polygonum for itching is grounded in traditional practice, with only indirect scientific support from related bioactivities, and not from robust clinical research.