Thrush is an acute, subacute and chronic disease of the oral mucosa caused by infection with Candida spp. Thrush is one of the types, called acute pseudomembranous candidiasis. The clinical manifestations are scattered curd-like white patches on the oral mucosa, which are common in newborns and small infants, especially in patients who have been using antibiotics or hormones for a long time. Infants are infected at birth because their mothers have Candida infection in the vagina; adults are less common, but it can occur in the chronically ill and frail, and in those infected with HIV. With the widespread use of immunosuppressants, broad-spectrum antibiotics, anti-tumor drugs, radiation therapy, organ transplantation, catheterization technology, especially the increasing incidence of AIDS, resulting in dysbiosis of the organism and oral flora, lower immune function, the incidence of oral candidiasis has increased significantly, and has now become one of the most common clinical diseases of oral mucosa. Whether oral Candida can cause disease depends on the virulence of Candida, the number, the pathway of invasion and the adaptability of the organism, the resistance of the organism and other factors. Infants and children, whose immune systems are not yet well developed, are good candidates for Candida infections. Among the susceptibility factors of oral Candida infection in adults, the most influential are systemic diseases and other oral mucosal diseases, such as after major surgery, tumor radiotherapy, dry syndrome, HIV infection, etc.