Desquamative gingivitis is a clinical finding with several potential etiologies. Among the most common are oral lichen planus, cicatricial pemphigoid, and pemphigus vulgaris, though various other differential diagnoses exist. The presence of desquamative gingivitis often results in poor oral hygiene, which can have downstream consequences, including periodontitis and tooth loss. Though certain mucosal findings may be suggestive of a particular diagnosis, a thorough history, physical examination, and appropriate dermato- and immunopathologic assessment is necessary for narrowing this broad differential diagnosis. This article offers a comprehensive review on the subject, including how to differentiate between the different underlying causes and the best methods for diagnosis (eg, how best to obtain mucosal biopsy specimens). In addition, there is minimal information in the dermatology literature on evaluation of oral hygiene and the consequences of poor oral hygiene not only on disease activity but also overall health. Knowledge on appropriate oral cavity inspection and evaluation of dental hygiene is lacking, and this continuing medical education series discusses methods to evaluate for these consequences so that the dermatologist can be better equipped in managing these patients and recognizing complications early on.