Hand, Foot and Mouth Disease (HFMD): What Causes It, How a Dermatologist Tells the Blisters Apart from Herpes and Chickenpox, Symptoms in Adults, Warning Signs, and Why Nails Fall Off After Recovery
Hand, Foot and Mouth Disease (HFMD) is a viral infection caused by enteroviruses. It causes fever, painful sores in the mouth, and blisters on the palms, soles and buttocks. It is common in young children during the rainy season and when school terms begin, but adults can get it too, and sometimes the illness is more severe than expected.
Most articles on the first page of Google explain this disease from a pediatrician’s point of view: “fever, blisters, clears up on its own in 7 days.” That is correct, but it is not enough, because the questions that really worry patients are often ones that need a dermatologist’s eye to answer: “Are these blisters really hand, foot and mouth disease, or herpes, chickenpox or an allergic rash?” In this article, Dr. Patara Voravutinon, a dermatologist, explains how the disease works, how to tell it apart from look-alike conditions, symptoms in adults, warning signs that need urgent medical attention, and something patients are often alarmed by but few people explain: why nails fall off after the illness has cleared.
What causes hand, foot and mouth disease?
Hand, foot and mouth disease is caused by infection with a group of viruses called enteroviruses (Human enterovirus). It is not caused by poor hygiene or poor parenting. A handful of virus strains are the main causes, and the differences between strains explain why some people have mild illness and others become seriously ill.
Coxsackievirus A16 — the most common strain, usually mild and resolving on its own.
Coxsackievirus A6 — causes a wider rash than usual that spreads beyond the palms and soles, and is an important cause of skin peeling and nail loss after recovery. It has been seen more often in recent years in both children and adults.
Enterovirus 71 (EV71) — the strain that needs the closest watch, because it is linked to complications of the brain and nervous system such as brainstem encephalitis and meningitis, which have caused deaths in several outbreaks in Asia.
The virus spreads in several ways at once: through nasal mucus, saliva, fluid from the blisters and stool, by close contact and by contaminated toys and objects. One important point many people do not know is that the virus can still be shed in stool for several weeks after the symptoms have gone, so washing hands after using the toilet and after changing diapers matters just as much as when the rash is still present.
What are the symptoms of hand, foot and mouth disease?
Symptoms usually appear in sequence rather than all at once on the first day. Understanding the sequence helps you recognize the illness sooner.
Early phase (first 1–2 days) — low to moderate fever, sore throat, tiredness and loss of appetite. Young children may be fussy and drool more.
Mouth sores (Enanthem) — red spots turn into small blisters that then break open into shallow, painful sores on the tongue, inside the cheeks, the palate and the throat, which makes children refuse to eat or drink.
Skin rash and blisters (Exanthem) — grayish blisters with a red ring around them appear on the palms, soles, between the fingers, around the nails and on the buttocks. Some people also get them on the arms, legs or genitals. The blisters of classic hand, foot and mouth disease are usually not very itchy, but feel painful or tight.
Overall, this illness clears up on its own within 7–10 days in most people and leaves no scars. What needs attention is not the rash itself, but preventing dehydration when a sore mouth makes a person refuse to eat or drink, and watching for the warning signs described below.
Incubation period, and how many days until recovery
Incubation period: about 3–6 days after exposure before symptoms begin. This is why it often spreads in groups at school or at home without anyone realizing.
Most contagious period: the first week of symptoms, but the virus can still spread through stool for several more weeks.
Recovery time: fever usually settles within 2–3 days, and the rash and mouth sores gradually improve and clear within 7–10 days.
A practical guideline is to stay out of school or work until the fever has gone and the blisters have dried and crusted over, which takes about 7 days, rather than returning as soon as the fever drops, because the period when the blisters still contain fluid is when the infection spreads most easily.
How to tell hand, foot and mouth disease from look-alike conditions (a dermatologist’s view)
This is the part that general information often skips, yet it is the heart of correct care, because “blisters” are not caused by just one disease. Telling them apart correctly changes both the treatment and what you need to watch for.
Herpes simplex
Herpes appears as clusters of small blisters packed together on a red base and often recurs in the same spot. In young children with a first herpes infection of the mouth, the sores are spread across the gums and the front of the mouth, unlike hand, foot and mouth disease, where the sores are usually at the back of the mouth and come with blisters on the palms and soles. If a painful blister keeps coming back on the tip of just one finger, think of herpes of the finger first. You can read more in our article on what causes herpes.
Chickenpox (Varicella)
Chickenpox usually appears all over the body, starting on the trunk and then spreading outward, with spots at several stages at the same time (red bumps, blisters and scabs). It is clearly itchy and often involves the scalp too. Hand, foot and mouth disease, on the other hand, concentrates on the hands, feet and inside the mouth, rarely affects the scalp, and is usually less itchy.
Herpangina
It is caused by the same group of viruses, but the sores are limited to the back of the mouth and the soft palate along with fever, and there is no rash on the hands and feet. It is a relative of hand, foot and mouth disease that shows up only in the mouth.
Allergic rash and itchy blisters on the hands (contact dermatitis / sweat blisters, pompholyx)
This group is mainly itchy, with no fever and no mouth sores. Small clear blisters that look like sago pearls usually appear on the sides of the fingers and on the palms and come and go repeatedly, which points to an inflammatory skin condition rather than a viral infection.
The fastest clue for telling them apart: hand, foot and mouth disease usually comes as a set, that is fever + painful mouth sores + blisters on the palms and soles together. If the mouth or fever element is missing, keep an open mind that it may be another condition.
Is hand, foot and mouth disease in adults more dangerous than people think?
Many people believe this disease only affects children, but adults can catch it too, especially parents and teachers who care for sick children. Some adults are infected with no symptoms or very mild ones, yet they can still pass the virus to others.
On the other hand, some adults, particularly those infected with Coxsackievirus A6, may have a wider rash and blisters than children, a lot of pain, and later peeling of the skin on the palms and soles and loss of nails. Groups who need particular care are pregnant women close to delivery and people with weakened immunity, who should consult a doctor if they suspect infection.
Treating hand, foot and mouth disease, and how much can be done at home
The key point to understand is that there is no specific antiviral medicine for this disease. All treatment is supportive, based on symptoms, so the body can clear the virus itself. The real goal is therefore to keep the person able to eat and drink and to watch for complications.
Reduce fever and pain with paracetamol dosed according to weight and age. Avoid taking more than the recommended dose.
Focus on fluids. Give frequent sips. Cold items such as cold water or ice cream can ease mouth pain. Avoid very hot, very sour or spicy foods and fizzy drinks.
Eat soft foods that are mild in flavor and cold or at room temperature, so they are easier to swallow.
Care for the skin blisters by keeping them clean and dry. Do not pop or squeeze the blisters, as this risks a secondary bacterial infection.
Use separate personal items and rest at home until the fever is gone and the blisters have dried.
Home care is appropriate when symptoms are mild, the fever is not very high and the person can still eat and drink normally, but you need to know where the “line” is, when home care is no longer enough, which is covered in the next section. What is not necessary and should not be done is buying antibiotics to take on your own, because this illness is caused by a virus, so antibiotics do not help and may cause unnecessary side effects.
Warning signs of hand, foot and mouth disease that need urgent medical attention
Although most cases clear up on their own, a small number progress to involve the brain or heart, especially with the EV71 strain. These signs usually appear within the first 2–3 days of fever, so this is the period to watch closely. Go to the hospital immediately if any one of the following occurs.
A fever above 39 degrees Celsius or a fever that does not come down for more than 48–72 hours.
Drowsiness, difficult to wake, not playing, not responding as usual.
Repeated startling jerks, muscle twitching, unsteady walking or seizures.
Fast breathing, breathlessness or a bluish color of the skin.
Heavy vomiting, or being unable to eat or drink at all, with signs of dehydration such as a dry mouth, much less urine, or crying without tears.
Dehydration from a sore mouth is the most common complication, while brain and heart complications are uncommon but serious. Knowing these signs in advance is the most important part of caring for this illness.
Why nails fall off or skin peels after recovering from hand, foot and mouth disease
This is a question that alarms parents a great deal, yet almost no article explains it. 2–8 weeks after recovering from hand, foot and mouth disease, some people find that their fingernails or toenails peel off (Onychomadesis) or that the skin on the palms and soles peels in sheets. This is seen more often in people infected with Coxsackievirus A6.
What we want you to be reassured about is that this condition is temporary and not dangerous. It results from the growth of the nail and skin being interrupted during the illness, and it is not a nail infection. A new nail normally grows in to replace it on its own without any special treatment. However, if only one nail is abnormal, thickened, misshapen, dark in color, or the problem lasts longer than expected without a clear history of hand, foot and mouth disease, you should have a dermatologist check it to rule out other causes, such as a fungal infection or other nail disorders. You can read more in our articles on nail disorders: telling abnormal nail changes apart, and what causes black nails and whether they are dangerous.
When the rash is unusually widespread, or occurs in people who already have eczema
In people who already have atopic dermatitis, infection with Coxsackievirus A6 may cause blisters to appear densely in the areas previously affected by eczema, a condition called Eczema coxsackium. It can look alarming and resemble other, more severe infections. A case like this should be examined by a dermatologist to reach a clear diagnosis, because caring for already inflamed skin together with a viral infection needs special care. You can read more about eczema in our article on atopic dermatitis.
Common myths about hand, foot and mouth disease
“Once you’ve had it, you won’t get it again” — not true. The disease is caused by several virus strains, and having had one strain does not protect against the others, so it can recur.
“Putting toothpaste or aloe vera on the blisters will help” — it does not, and it may cause irritation or reinfection. Let the blisters dry on their own and keep the area clean.
“It happens because the child isn’t kept clean” — not true. The disease spreads through contact with a virus that passes easily among children, and it is not the fault of the caregiver. Hand washing helps reduce spread, but it does not mean that people who get the disease are unclean.
“You need antibiotics to get better faster” — not true. Antibiotics have no effect on viruses. They are used only when a secondary bacterial infection occurs and must be prescribed by a doctor.
How to prevent spread at home and at school
Wash hands often with soap, especially before eating, after using the toilet and after changing diapers.
Clean toys, doorknobs and shared surfaces. These viruses resist alcohol gel better than many other viruses, so washing with soap and water or using a suitable disinfectant is important.
Keep personal items separate such as drinking glasses, spoons and towels while symptoms are present.
Keep a sick child home from school until the fever is gone and the blisters have dried, to reduce outbreaks in groups.
As for the vaccine, a vaccine against the EV71 strain is used in some countries, but it is not yet a standard general vaccine in Thailand. If you are interested, consult a doctor for an assessment based on your situation.
When to see a dermatologist
Most hand, foot and mouth disease clears up on its own and can be managed at home according to symptoms, but you should see a doctor if you are not sure whether the rash and blisters really are this disease, if the rash is unusually widespread or occurs in someone who already has eczema, if there is a nail abnormality that does not fit the history of hand, foot and mouth disease, or if there are any of the warning signs mentioned above. A correct diagnosis from the start allows care to be targeted, avoids unnecessary worry, and does not miss a condition that needs prompt treatment.
If you or someone in your household has a blistering rash and you are not sure what it is, the dermatologists at Siam Dermatology are glad to give advice and examine you so the condition is clearly identified before care begins.
Frequently asked questions about hand, foot and mouth disease
What is the incubation period of hand, foot and mouth disease?
About 3–6 days after exposure before symptoms begin, which is why it often spreads in groups at school or at home before anyone realizes.
How many days does hand, foot and mouth disease last?
In general, fever settles within 2–3 days, and the rash and mouth sores clear within 7–10 days. Stay out of school or work until the fever has gone and the blisters have dried and crusted over, which takes about 7 days.
Can adults get hand, foot and mouth disease?
Yes, especially people who care for sick children. Some have mild symptoms or none but can still spread the virus, while others have a widespread, very painful rash. Pregnant women close to delivery and people with weakened immunity should consult a doctor if they suspect infection.
How is hand, foot and mouth disease different from chickenpox and herpes?
Hand, foot and mouth disease centers on blisters on the palms and soles and sores in the mouth, and is usually not itchy. Chickenpox appears all over the body starting on the trunk, with spots at several stages at once, and is clearly itchy. Herpes appears as clusters of blisters packed together and often recurs in the same place.
Can hand, foot and mouth disease be treated at home?
Mild cases in which the person can still eat and drink can be managed at home by reducing fever and pain, focusing on fluids and eating soft foods. Do not squeeze the blisters. Watch for warning signs such as a fever that will not come down, drowsiness, twitching, breathlessness or dehydration, and seek medical care immediately if any of these appear.
Why do nails fall off after recovering from hand, foot and mouth disease?
Nail growth is interrupted during the illness, so the nail can peel off 2–8 weeks after recovery. It is common with the Coxsackievirus A6 strain. It is temporary and not dangerous, and a new nail grows in on its own. But if only one nail is abnormal or the problem lasts unusually long, have a dermatologist check it.
Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed August 8, 2026
The information in this article is for general education only and cannot replace diagnosis and treatment from a doctor who examines you personally. If you have unusual symptoms or any warning signs, consult a doctor.
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