Prune tongue is mainly manifested as smooth tongue surface like flesh red, the tongue body may appear enlarged, congestion and redness, etc. Some patients may have superficial fissures on the tongue surface, and the tongue body extends out of the oral cavity like a ripe prune, so it is called prune tongue. Generally speaking, prune tongue is a typical symptom of scarlet fever and Kawasaki disease.1. Scarlet fever: Scarlet fever is an acute respiratory infectious disease caused by group A hemolytic streptococcal infection, patients have fever, mostly accompanied by headache, general malaise, and other symptoms, most of them have a rash on the second day of fever, which spreads all over the body from the back of the ear, neck, and upper chest, and the swelling of the papilla of the tongue can appear at the same time as the rash, covering the white moss, and the swollen papilla of the tongue protrudes beyond the white moss, and forms a thick, red tongue. The swollen papilla of the tongue protrudes beyond the white moss, forming strawberry tongue or prune tongue. The treatment is based on antibacterial therapy, and penicillin is often applied; 2. Kawasaki disease: it is a common acute self-limiting vasculitis in childhood, which may be related to infection, autoheredity, immune abnormality, etc. It manifests as persistent high fever, with congested conjunctiva of the eyeballs and conjunctiva, red mouth and lips accompanied by dry cracks, and a rash appears 2-3 days after the onset of the disease, accompanied by hard edema of the back of the hands and feet and swelling of the lymph nodes in the neck. Treatment may include aspirin to inhibit platelet aggregation, intravenous immunoglobulin or glucocorticoids such as methylprednisolone to reduce coronary artery damage, and surgery if necessary.