Background: Oral melanoacanthoma is not common. It occurs mostly on the buccal mucosa. Since it happens suddenly and progresses rapidly, it clinically resembles melanoma. Melanoacanthoma occurs in regions susceptible to trauma. The clinical presentation of the lesion is not enough to diagnose it; therefore, tissue biopsy is necessary to exclude malignancy. Case report: We report a case of oral melanoacanthoma in a rare mucosal location in a 21-year old female patient in whom generalized gingival melanoacanthoma was related to the use of the teeth whitening strips. This irritating factor increased melanocyte activity in the gingival tissues and labial mucosa. Discussion: Oral melanoacanthoma is a rarely encountered pigmented lesion in the oral cavity and is especially uncommon in the gingiva. It is a reactive lesion affecting the mucous membranes with no risk of malignant transformation. This case report shows that teeth whitening strips may trigger oral melanoacanthoma in susceptible individuals. Long-term irritation of the oral tissues may increase the number of dendritic melanocytes throughout the epithelium and accordingly increase the brown pigmentation of the oral cavity. Eliminating all possible local sources of irritation and ruling out other causative factors are the standard first step in the treatment of oral melanoacanthoma. Conclusions: This case shows the importance of including oral melanoacanthoma in the differential diagnosis of diffuse gingival pigmented lesions.