This study consists of a literature review with the objective of evaluating whether there are important drug interactions between allopathic medicines and herbal medicines when used concomitantly, in addition to understanding how these interactions can manifest themselves, in order to maximize the therapeutic effect, listing the potential effects adverse triggers. Pubmed, Lilacs, Virtual Health Library (VHL), and Google Scholar databases were used. The main results showed that the main medicinal plants used as raw material for herbal medicines that are used together with allopathic medicines are: Matricaria recutita L. (Chamomile), Hypericum perforatum L. (St. John's wort), Ginkgo biloba L., Valeriana officinalis L. and Passiflora incarnata L. It was found that herbal medicines have the potential to cause, in addition to drug interactions, a series of adverse reactions, including, from effects on the central nervous system, to effects on metabolism, hormonal control, cardiac, digestive function, among others. This profile highlights the need for further studies to understand the mechanisms of interaction and promotion of training for health professionals for the rational use of herbal medicines.