This study aims to explore the different connotations and potential offensiveness of ten mechanistic labels in newly referred Mexican patients with rheumatic symptoms as well as in Mexican and Canadian rheumatologists. Patients with musculoskeletal complaints newly referred for a rheumatology assessment were interviewed consecutively before they saw the rheumatologist. Patients were asked to choose one of nine feelings provoked by ten different illness mechanism labels. Rheumatologists gave a medical diagnosis after seeing the patients. Mexican and Canadian rheumatologists were invited to answer a structured questionnaire about their feelings at the moment they identified each of the ten different provided scenarios. Patients' and rheumatologists' feelings were classified as "offended" or "nonoffended." The "offensive score" was used to calculate a "number needed to offend" (NNO). One hundred and fifty patients were included. Inherited, immunological, and inflammatory labels had the fewest negative connotations (NNOs 17, 12, and 14, respectively), and psychological, functional, idiopathic, and sleep disturbance labels had the most (NNO 2 and 3, respectively). Functional labels were almost four times more offensive than organic labels. Stratified by rheumatologist diagnosis, patients with functional disorders were more accepting of organic-based mechanistic labels. A higher potential to offend was observed when patients with functional somatic conditions were given functional mechanistic labels (NNOs 1 to 4). The survey was completed by 186 Mexican rheumatologists and 71 Canadian rheumatologists. Primarily functional disorders such as somatization and anxiety had a high potential to evoke offensive feelings (NNOs 3 to 7). No significant differences in the NNO were found between Mexican and Canadian rheumatologists. Getting or giving mechanistic/explanatory labels is emotional. Both patients and rheumatologists experienced offended feelings with functional or idiopathic labels.