Black tongue (BT) is a benign, self-limiting black discoloration of the lingual mucosa due to different factors. Only a few pediatric cases of BT related to drug intake are described. We report a child with BT developed after amoxicillin/clavulanic acid intake and also made a review of the pediatric cases of black tongue reported in literature after drugs. The child underwent allergy work-up with in-vivo and in-vitro tests, showing a positive lymphocyte transformation test (LTT) for amoxicillin and amoxicillin/clavulanic acid. For the first time, BT was proved to be a hypersensitivity reaction to drugs, suggesting a possible role of a T-cell mediated mechanism. Even if already reported as a mild side effect, according to our results, allergy investigations are essential to make a confident diagnosis and to give further indications to patients about the discontinuation of the culprit drug.