Thrush is a fungal infection that commonly occurs in infants and young children, especially those with weakened immunity due to prolonged use of immunosuppressants or steroids. It is caused by the infection of oral mucous membranes by Candida albicans. Commonly affected areas include the oral cavity, mucous membranes, gums, and tongue. It appears as white patches on the mucosa that generally cannot be wiped off with a cotton swab. Forceful wiping may lead to bleeding. Treatment mainly involves topical medication, a light diet, and maintaining good oral hygiene, which is very important.