Medicinal plants (MP) have been used world-wide for the treatment or prevention of health conditions and due to their natural origin; they have been historically considered harmless. Semi-structured interviews were carried out with an intentional sample of twenty plant vendors in the city of Diadema to explore their knowledge and beliefs on the safety and efficacy of MP. Different levels of perceptions about the safety of MP were found, varying from "completely safe" to "completely harmful". The majority of the interviewees declared that "if herbs have an effect, they are also likely to have a side effect", depending on many factors such as dosage, concomitant use of other drugs, characteristics of the plant material and consumer related factors, specially those related to pregnant women, children and elderly people. Thirty-nine unexpected events related to 21 species of MP were reported. One case of serious gastrointestinal disease related to the consumption of a contaminated "slim mixture" was also described. Adverse events and other problems that result from MP are relatively uncommon, but they are almost certainly underreported and occur more often than acknowledged. This study strengthens the call for further research and educational efforts into this complex area.
medicinal herbs; plant vendors; qualitative research; safety
