How to bridge the gap? European medical plants used for treating oral mucositis: on the search for evidence.

Oral mucositis is a common, painful side effect of cancer treatment-be it locoregional (e.g. irradiation) or systemic (e. g. chemotherapy). Phytotherapy is often used by patients to alleviate symptoms. However, knowledge on which medical plants are recommended by literature about Traditional European Medicine (TEM), their effect(s) on symptoms and their efficacy is severely lacking. Therefore, we developed a novel approach to assess traditional knowledge of herbals used in TEM and searched the online databases for studies reporting effects of these plants.At first, online research did not yield a satisfying number of studies (MESH terms: "mucositis" OR "stomatitis" AND "herbal" OR "herbal medicine"). Trials were labelled by the country conducting the study. In parallel, we compiled a list of 78 plants recommended for treating oral mucositis by screening 14 books on TEM. Then, a "hit list" of the plants most often mentioned was composed and used further for a second online investigation using the Latin plant designations as MESH term. Studies of both online searches were pooled for analysis.There is a gap between traditional knowledge and trials investigating medical plants used by TEM. Overall, herbal remedies alleviate oral mucositis and especially, gingivitis well. There is good evidence for using Matricaria recutita L., Salvia officinalis L., Calendula officinalis L. and Thymus spp. L. for treating oral mucositis.Clinical trials investigating medical plants known in TEM are rare. However, following our research strategy, we could extrapolate four plants with good evidence for alleviating symptoms of oral mucositis and gingivitis.