Conflict of interest: none declared. White sponge naevus (WSN) is a rare condition affecting the mucous membranes, especially the oral mucosa. WSN appears to follow a hereditary pattern, although cases with no family history have been reported.1 Genetic studies have associated the development of WSN with mutations in keratins 4 and 13.2 Treating WSN is still a challenge. Some benefits have been reported with the use of antibiotics such as penicillin and tetracycline.1, 3, 4 This study assessed the clinical response of WSN to 0.25% aqueous tetracycline mouth rinse. Four cases of WSN affecting three women (aged 23, 27 and 46 years) and one man (aged 24 years) were evaluated Bilateral involvement of the buccal mucosa was seen in three patients, and the fourth presented lesions only of the labial mucosa. WSN diagnosis was based on clinical and histopathological findings (Fig. 1a,b). Treatment consisted of 0.25% aqueous tetracycline mouth rinse (5 mL for 1 min) twice daily for up to 12 weeks. Responses to the treatment are summarized in Table 1. Patients 1 and 2 were more resistant to treatment, showing only partial improvement (Fig. 2a,b). The other two patients, who had no familial members affected (cases 3 and 4), showed excellent response (Fig. 3a,b). During this treatment, one patient tested positive for Candida and was treated with nystatin. Mild recurrence was observed in one patient and was given a further short course of tetracycline, which promptly resolved the lesions.