摘要： This study aimed to evaluate the reduction of halitosis when using antimicrobial photodynamic therapy (aPDT) with Bixa orellana extract and blue light-emitting diode (LED). Methods: Forty-four UNINOVE students or employees with a diagnosis of sulfide (H2S) ≥ 112 ppb in gas chromatography were selected. The patients were randomly divided in groups: Group 1 (n=15): aPDT with annatto and LED; Group 2 (n=14): tongue scraping; Group 3 (n=15): tongue scraping and aPDT. For aPDT, a was Bixa orellana extract used in a concentration of 20% w/v (Fórmula e A??o?, S?o Paulo, Brazil) on the tongue for 2 minutes, associated with a blue-violet LED (Valo Cordless Ultradent? Products, Inc., South Jordan, UT, USA) (395-480 nm). Six points were irradiated on the back of the tongue, at wavelength 395-480 nm for 20 seconds, energy of 9.6 J and radiant energy of 6.37 J/cm2 per point. The results were compared before, immediately after treatment and 7 days after. The Friedman test was used for the intragroup analysis and the Kruskal Wallis test for the intergroup analysis. Results: In all groups, there was a difference between baseline and the value immediately after the treatment. In Groups 1 and 3, there was no difference between the baseline and the 7 days control. Conclusion: There was an immediate reduction of halitosis, but the reduction was not maintained after 7days.