The most common complication of hand-foot-and-mouth disease (HFMD) is dehydration. The illness can cause painful lesions in the mouth and throat, making swallowing difficult. Therefore, it is crucial for patients, especially children, to maintain adequate fluid intake to prevent dehydration. In cases of severe dehydration, intravenous (IV) fluid therapy may be required in a hospital setting.

Although HFMD is generally a mild illness, it can rarely lead to serious complications. The enteroviruses causing the disease can, in some instances, reach the central nervous system and result in life-threatening conditions. These potential severe complications include:

* Viral Meningitis: This is an infection and inflammation of the membranes (meninges) surrounding the brain and spinal cord, and the cerebrospinal fluid.
* Encephalitis: A serious and potentially life-threatening condition involving inflammation of the brain.