Bougainvillea has a history of use in traditional medicine systems, particularly in parts of South America and Asia, where it is sometimes applied topically or used in preparations to address skin conditions, including rashes and hives. Folk remedies may involve the use of bougainvillea leaves or flowers as poultices or infusions, with the belief that the plant possesses anti-inflammatory or soothing properties. However, documentation of these practices is generally found in ethnobotanical surveys or local herbal medicine records, rather than in rigorous clinical trials.

Scientifically, there is very limited evidence supporting the efficacy of bougainvillea for treating rashes or hives. While a few laboratory studies have highlighted the presence of bioactive compounds in bougainvillea species (such as flavonoids and saponins) with general anti-inflammatory or antimicrobial effects, there are no direct clinical studies or robust animal models specifically examining its effectiveness for dermatological conditions like rashes or hives. Overall, the use of bougainvillea for these conditions is supported more by traditional use and anecdotal reports than by scientific validation.