Twenty patients will be selected from the outpatient clinic of the department of Oral Medicine, Periodontology, and Oral diagnosis, Faculty of Dentistry, Ain Shams University and will be divided into two groups (test group and control group), 10 in each group. Ten patients will receive Nigella Sativa oil mouth rinse. Ten patients will receive the placebo isotonic (normal saline) with concentration 0.90% of sodium chloride (NaCl). At the screening visit, patient history will be documented, and subjects who met the inclusion/exclusion criteria were asked to complete the survey to determine the severity of their symptoms prior to clinical examination. The oral examination will be a routine visual assessment to document the presence, location and size of an ulcerative oral mucosal lesion.

Patients will be asked to use the NS oil mouth rinse (10 ml each 6 hrs.) four times daily. Subjects will be provided with 72 hours supply of the study product.

Patients will be instructed to use it for 72 hours with a minimum frequency of four times per day, swished for one minute at each use, in which the first dose was used upon awakening and the last dose just before evening sleep. Patients will be instructed not to use over the counter (OTC) or pharmacy formulated oral rinses or gels during the active treatment phase. The same procedure will be done in the control group but by using isotonic (normal saline) with concentration 0.90% of sodium chloride (NaCl). The patients will be re-examined after 24, 48, 72 hrs. from the beginning of the treatment until the complete healing of the (RAU). When patients completed the follow-up phase after product use, they will be asked to repeat the surveys in which they documented the pain scores and oral symptoms. The ulcer size will be measured using periodontal calibrated probe before treatment and after 24, 48, 72 hrs. of treatment until the complete healing of the (RAU).Clinical photographs of the ulcers will be taken using a digital camera preoperatively and after 24, 48, 72 hrs. of treatment until the complete healing of the (RAU). Patients of discomfort and pain severity will be rated at baseline, 24, 48, 72 hours and day seven after using the study product by numeric rating scale (NRS) and visual analog scale for pain (VAS) since, the association between NRS and VAS would be stronger.

The salivary TNF-α levels in RAS patients can be detected by using saliva as a convenient medium and it will be measured prior to the definitive therapy and at the end of using the study product. Distilled water was given to the patients to rinse their oral cavity for 1 minute to remove any debris. Under aseptic conditions, a minimum of 2 ml of saliva will be collected from the patient through 'Spit Technique' after oral rinse with water at room temperature into sterilized tubes every minute for 8-10 minutes. The saliva samples will be collected after one hour or more since the last food intake. The patients will be asked to avoid drinking one hour before sampling. Samples will be immediately frozen at -20°C .The estimation salivary contents of TNF-α will done by enzyme linked immunosorbent assay using a commercial ready-made ELISA kit.