Herpes stomatitis (or oral herpes) is an acute infection of the mouth cause by the herpes simplex virus The infection is common and often asymptomatic. However, some children get numerous small, shallow ulcers on the tongue, gums and mucosa inside the cheeks. As the ulcers are very painful the child salivates and often refuses to eat or drink. The child is also pyrexial and generally unwell. The stomatitis slowly resolves by 10 days. An important complication of herpes stomatitis is dehydration.

Undernourished children with measles, and children with AIDS, are at high risk of severe herpes stomatitis. Children may also have severe stomatitis due to oral candidiasis.