Hand, foot, and mouth disease is one of many infections that cause mouth sores. Health care providers can usually identify mouth sores caused by hand, foot, and mouth disease by considering —
how old the patient is,
what symptoms the patient has, and
how the rash and mouth sores look.
Depending on how severe the symptoms are, samples from the throat or feces (stool) may be collected and sent to a laboratory to test for the virus.