The spots, patches and discoloration that tongues can develop may be harmless, but occasionally they're a sign of something serious. Black spots on tongue .
These projections of tissue trap and collect bacteria and other substances, and this can cause tongue discoloration. Occasionally, shedding doesn't take place .
The image (Figure 1) shows small, hyperpigmented papules on the anterior and lateral aspects of the dorsal tongue. Dermoscopy shows light to dark brown .
Tongue Discoloration and Other Changes – Learn about the causes, symptoms, diagnosis & treatment from the Merck Manuals – Medical Consumer Version.