Materials and methods. Thirty patients participated in this randomized clinical trial from April 2010 to June 2010 (Trial Registration Number: NCT01375101). Patients were randomly allocated in two groups. Both groups received the standard treatment (dexamethasone mouthwash and nystatin suspension). Experimental group received oral 250 mg quercetin hydrate capsules (bid) and the control group received placebo capsules. The pain and severity of the lesions were recorded at the initial visit and the follow-ups. All recorded data were analyzed with chi-square, Mann-Whitney, t-test, Wilcoxon and Friedman tests using SPSS 11.5.

Results. There were no significant differences between the two groups in severity of the lesions and pain in the follow-ups. According to the Friedman test, there was a significant reduction in pain (P = 0.01) and severity indices (P = 0.00) in the case group. These differences were not observed in the control group (P = 0.26, SI and P = 0.86, PI). No adverse effect of quercetin was reported. 

Conclusion. According to the results, no significant therapeutic effect can be considered for quercetin in treatment of OLP.