Smartweed (Polygonum hydropiper), also known as water pepper, has a long history of traditional use in herbal medicine for a variety of ailments, including skin conditions such as carbuncles. Historical herbal texts and ethnobotanical records indicate that traditional healers in Europe, Asia, and North America used poultices or topical preparations of smartweed leaves to address boils, carbuncles, and other localized skin inflammations. The rationale behind its use primarily stems from its reputed astringent, anti-inflammatory, and mildly antiseptic properties, which were believed to help reduce swelling, draw out infection, and promote healing.

However, scientific validation for these practices is limited. While smartweed contains various phytochemicals such as flavonoids and tannins, which have demonstrated anti-inflammatory and antimicrobial activity in laboratory settings, there is a lack of controlled clinical studies specifically investigating its efficacy for carbuncles or similar skin infections. The rating of 2 reflects that, although the traditional use is well-documented, the supporting scientific evidence remains preliminary and indirect. Most modern medical guidelines do not include smartweed as a recommended treatment for carbuncles, and its use persists mainly in folk and complementary medicine traditions.