Bittersweet (Solanum dulcamara) has a long history of use in traditional European herbal medicine for skin conditions, including rashes and hives. Historical texts from the 16th through 19th centuries reference its use as a topical and internal remedy for various dermatological complaints, such as eczema, psoriasis, and other eruptive skin diseases. The plant contains glycoalkaloids, such as solanine and dulcamarine, which were believed by herbalists to have anti-inflammatory and depurative (blood-purifying) effects. Traditional herbalists often prepared ointments or decoctions from the stems or leaves for external application to inflamed skin.

Despite its traditional use, modern scientific studies specifically evaluating Bittersweet for the treatment of rashes or hives are lacking. There is no robust clinical evidence supporting its efficacy or safety for these conditions. Moreover, the presence of toxic alkaloids in the plant raises safety concerns, especially with internal use. While the historical record demonstrates its longstanding use for dermatological issues, contemporary herbal pharmacopoeias generally caution against its use due to potential toxicity.

In summary, Bittersweet's application for rashes and hives is primarily rooted in tradition, with minimal scientific validation and notable safety concerns.