Whitish patches on the tongue, similar to those sometimes found inside the cheeks, may be due to Fever Dehydration Mouth breathing Secondary syphilis Oral candidiasis (thrush) Lichen planus Leukoplakia Changes in the Mouth and Tongue Candidiasis (Oral) Oral candidiasis takes many forms, including angular cheilitis and pseudomembranous plaques on the oral mucosae, which can be associated with dentures, as in this image (top), or develop on the tongue (bottom) or pharynx.