Hand, foot, and mouth disease is almost always mild. About 86% of cases involve nothing more than a low fever, mouth sores, and a rash that clears up on its own within 7 to 10 days. Serious complications exist but are rare, affecting roughly 1% of cases, and deaths are extremely uncommon at about 0.03% of reported cases. If you or your child has it, the overwhelming odds are that it will be an uncomfortable but short-lived illness.
What a Typical Case Looks Like
Symptoms usually appear 3 to 6 days after exposure to the virus. The first signs are a fever and sore throat, sometimes with a general feeling of being unwell and a loss of appetite. Within a day or two of the fever starting, painful blister-like sores develop in the mouth, mostly toward the front or in the throat. A rash then appears on the hands, feet, and sometimes the buttocks. The rash can look like flat red spots or small blisters, and while it’s not usually itchy, the mouth sores can be genuinely painful, especially in young children.
Nearly all people recover in 7 to 10 days with little or no medical treatment. The fever typically breaks first, followed by gradual healing of the sores and rash. About 13% of infections are completely asymptomatic, meaning the person never develops symptoms at all.
When It Becomes More Than Mild
The seriousness of hand, foot, and mouth disease depends heavily on which virus caused it. The illness is most commonly caused by one of two viruses: coxsackievirus A16 and enterovirus A71. Coxsackievirus A16 is associated with mild, self-limiting illness and attracts very little clinical concern. Enterovirus A71 is a different story.
In one study, 21% of children infected with enterovirus A71 experienced severe complications, including problems affecting the brain and heart. This particular strain can cause encephalitis (brain inflammation), aseptic meningitis, acute flaccid paralysis (a polio-like weakness in the limbs), and in the most extreme cases, cardiopulmonary failure. These outcomes are rare in the overall population of HFMD cases but are the reason the disease occasionally makes headlines during outbreaks, particularly in parts of Asia. Between 2008 and 2014, China reported more than 10 million cases and approximately 3,000 deaths from HFMD, almost all linked to enterovirus A71.
You can’t tell at home which virus is responsible. In practice, the vast majority of cases in any given outbreak are mild regardless of the strain.
How Serious Cases Unfold
The rare progression from mild illness to dangerous complication follows a specific pattern. It starts with brainstem encephalitis, where the virus causes inflammation in the part of the brain that controls basic functions like breathing and heart rate. This brainstem damage triggers a flood of stress hormones that constrict blood vessels, force excess fluid into the lungs, and reduce the heart’s ability to pump effectively. At the same time, an overactive immune response increases the leakiness of blood vessel walls throughout the body. The combined effect can lead to heart failure and fluid in the lungs.
Warning signs that a case is becoming serious include high fever that won’t come down, unusual sleepiness or irritability, jerking or twitching movements, unsteady walking, rapid breathing, or a racing heartbeat. These symptoms typically emerge within the first few days of illness. Children under 5 are at highest risk for severe complications.
The Dehydration Problem
Even in mild cases, the most common practical concern is dehydration. The mouth sores can be so painful that young children refuse to eat or drink. This is the issue that most often sends families to a doctor or emergency room. Cold fluids, ice pops, and soft foods tend to be easier to tolerate than anything acidic or warm. If a child hasn’t urinated in several hours, has no tears when crying, or seems unusually lethargic, dehydration may be setting in.
Nail Shedding and Other Delayed Effects
One alarming but harmless aftereffect catches many parents off guard: nail shedding. Four to eight weeks after the illness resolves, some children (and adults) notice their fingernails or toenails loosening and partially or completely falling off. This is a known late complication of HFMD and, while it looks unsettling, the nails grow back normally without treatment. It doesn’t indicate that the illness was severe or that anything is still wrong.
Adults Can Get It Too
Hand, foot, and mouth disease is most common in children under 5, but adults are not immune. Adults who catch it tend to have the same symptoms: fever, mouth sores, and rash. The illness is generally mild in healthy adults, though the mouth pain can be surprisingly intense. People with weakened immune systems face a higher risk of prolonged or more severe illness.
How Long You’re Contagious
The virus spreads through saliva, blister fluid, nasal secretions, and stool. You’re most contagious during the first week of illness, but the virus can remain in stool for weeks after symptoms resolve. The CDC’s guidance for children returning to school or daycare is straightforward: they can go back once they have no fever, feel well enough to participate, and aren’t drooling excessively from mouth sores. There’s no mandatory exclusion period based on the rash alone, since the virus continues to shed regardless of whether blisters are still visible.
Frequent handwashing, especially after diaper changes and before preparing food, is the most effective way to limit spread within a household. Disinfecting shared surfaces and toys also helps, since the viruses that cause HFMD can survive on hard surfaces for several hours.