Fever and red tongue may be caused by scarlet fever and other diseases, as follows. Scarlet fever is an acute respiratory infectious disease caused by group A hemolytic streptococcal infection, and the main clinical manifestations include fever, headache, sore throat, general malaise, diffuse bright red rash all over the body, and bacillary papillitis. Among them, bacillary papillitis is a swelling, congestion, burning of the bacillary papillae distributed in the anterior part of the tongue and the tip of the tongue, and its epithelium is thin and crimson, resulting in the anterior part of the back of the tongue resembling a prune, which is known as “prune tongue”. The patient may experience pain and discomfort. Fever and red tongue may have other causes, it is recommended to go to the hospital in a timely manner to clarify the cause of the disease for targeted treatment.