Is There a Test for Hand, Foot, and Mouth Disease?

Lab tests for hand, foot, and mouth disease do exist, but most children never get one. The illness is usually recognized on sight and clears up by itself, so a test rarely changes what you do at home.1News-Medical. Diagnosis of hand foot and mouth disease Where testing earns its place is in working out which virus is behind an unusual or serious case, more than in confirming an ordinary one.

How Doctors Usually Diagnose It Without a Test

Doctors usually diagnose hand, foot, and mouth disease from a physical exam alone.2News-Medical. Diagnosis of hand foot and mouth disease The illness has two telltale features: ulcers in the mouth and small blisters on the hands, feet, buttocks, genitals or diaper area.3News-Medical. Diagnosis of hand foot and mouth disease The doctor also weighs your child’s age and symptoms alongside what the rash looks like.4Mayo Clinic. Hand-foot-and-mouth disease: Diagnosis and treatment

The pattern matters more than any single spot, because mouth sores alone or a rash alone show up in many childhood illnesses. The rash on the palms and soles can be flat red spots or small blisters, and it isn’t always itchy or painful. Some children have only a few spots, or only the mouth sores, and a doctor can still reach the diagnosis when the other features and the exposure fit.

The doctor is also quietly checking for signs that the illness is more than routine, such as dehydration, a stiff neck or unusual drowsiness. Finding none is part of why a test can be skipped: the child can safely recover at home. If the picture doesn’t fit, the doctor may consider other causes and decide whether a test is needed.

Skipping the test is usually reasonable because most cases are uncomplicated and clear on their own in 7 to 10 days.5News-Medical. Diagnosis of hand foot and mouth disease Treatment is the same whether or not a lab confirms it: fluids, rest and pain relief. An exam-based diagnosis is usually enough for a daycare or school note.

When a Lab Test Is Worth Doing

One strain, coxsackievirus A6, has spread and causes rashes that don’t look like classic hand, foot, and mouth disease.6PubMed Central. Atypical Hand-Foot-Mouth Disease Associated with Coxsackievirus A6 Infection When the rash is widespread or atypical, doctors may order a lab test to confirm the diagnosis.7PubMed Central. Atypical Hand-Foot-Mouth Disease Associated with Coxsackievirus A6 Infection Atypical cases can look so much like chickenpox that symptoms alone can’t reliably tell them apart.8PubMed Central. Clinical features of poorly distinguishable HFMD and chickenpox in children: a retrospective analysis

With this strain, the rash may spread beyond the hands, feet and mouth to the arms, legs, face or trunk. The spots can look like larger blisters or crusted, eczema-like patches, particularly where a child already has irritated skin. Because the picture is so different from the classic one, a parent may not suspect the illness, and a doctor may want the lab to confirm it.

Severe illness is another reason. In a child admitted with possible meningitis, testing spinal fluid for enterovirus can confirm a viral cause.9AAP Grand Rounds. Utility of Enterovirus PCR Testing of CSF In one hospital study, a positive result meant shorter stays (median 42 vs 72 hours), fewer extra tests and fewer days of antibiotics.10AAP Grand Rounds. Utility of Enterovirus PCR Testing of CSF

Spinal fluid is sampled with a needle in the lower back, a step reserved for a child who appears seriously ill. Doctors often start antibiotics for possible meningitis until they know whether the cause is bacterial or viral.

Pregnancy is a third case. When a pregnant woman has the illness, swabbing a blister found the virus in about 7 of 10 cases, while blood tests rarely did.11PubMed. Hand, foot, and mouth disease in pregnancy: 7 years Tuscan experience and literature review If you are pregnant and have symptoms, tell your obstetrician, who can decide whether testing is useful.

Health departments also sometimes test samples to learn which virus is circulating. This helps spot more dangerous strains like enterovirus 71 early. The result usually doesn’t change care for your individual child.

Call the doctor or go back if your child:

  • refuses to drink or has few wet diapers, which are signs of dehydration
  • has a fever lasting more than three days, or a very high fever
  • has a stiff neck, unusual sleepiness, jerking movements or trouble walking
  • breathes fast or with effort
  • is a baby under a few months old with fever and rash

What the Test Involves and Which Sample Works Best

If testing is done, the doctor usually takes a throat swab or stool sample and sends it to a lab.12Mayo Clinic. Hand-foot-and-mouth disease: Diagnosis and treatment The lab runs a PCR test, which looks for the virus’s genetic material. PCR detects tiny amounts of genetic material, so it works even when little virus is present, and it is faster than growing the virus in a dish. Some lab tests can detect enterovirus 71 and other enteroviruses at the same time in one run.13PubMed Central. Diagnosis of hand, foot, and mouth disease caused by EV71 and other enteroviruses by a one-step, single tube, duplex RT-PCR

The choice of sample makes a big difference:

A throat swab takes a few seconds and may cause brief gagging. A stool sample can be collected at home from a diaper or potty into a cup. A rectal swab is quick and used when stool isn’t available. Blister fluid is gently swabbed from an open or opened blister.

Stool is the most reliable sample in the figures, but a throat swab is easier to take, so doctors often weigh convenience against accuracy. If the first sample is negative but suspicion remains, a second sample type can improve the chance of finding the virus.

A negative result doesn’t rule the illness out. A single swab misses about 1 in 5 infections, and results usually take one to several days, often after symptoms are easing. If the test is negative but the signs fit, doctors still rely on the exam.

Blood antibody tests aren’t the main tool. Antibodies made against one enterovirus often react to related ones too,19PubMed Central. Cross-Reactive Antibody Responses against Nonpoliovirus Enteroviruses so a blood antibody result can’t reliably tell enterovirus 71 from coxsackievirus A16.20PubMed. Cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with Enterovirus 71 and Coxsackievirus A 16 Coxsackievirus A6 isn’t picked up by standard antibody tests and grows poorly in lab cultures, so PCR is needed.21Cutis. Hand-foot-and-mouth Disease Caused by Coxsackievirus A6 on the Rise

Telling HFMD Apart From Chickenpox and Other Rashes

Classic hand, foot, and mouth disease and chickenpox can usually be told apart by where the rash is and how it looks.22PubMed Central. Clinical features of poorly distinguishable HFMD and chickenpox in children: a retrospective analysis Sores inside the mouth and spots on the limbs and around the lips point toward hand, foot, and mouth disease. A very itchy or widespread rash points toward chickenpox.23PubMed Central. Clinical features of poorly distinguishable HFMD and chickenpox in children: a retrospective analysis

How the spots develop helps too. Chickenpox typically appears in crops, so new bumps, blisters and scabs can all be present at once. Classic hand, foot, and mouth spots usually concentrate on the hands, feet and around the mouth rather than spreading across the whole body, though the coxsackievirus A6 strain can spread more widely. Mouth sores are common in the illness, though chickenpox can occasionally cause them too, so a doctor weighs the whole picture rather than one sign.

Other look-alikes are easier to separate. Herpes mouth sores tend to involve swollen, bleeding gums and lips. Strep throat causes sore throat and fever but no hand or foot rash. Insect bites appear in clusters on exposed skin, without mouth ulcers. Eczema flares are dry and itchy and not tied to a fever, though coxsackievirus A6 can cluster on eczema-prone skin.

Chickenpox is worth ruling out because it can be risky for newborns and for pregnant people who aren’t immune. Unlike hand, foot, and mouth disease, it has a vaccine and an antiviral treatment.

How Long Your Child Stays Contagious

People are contagious while ill and possibly for several weeks after.24Sarpy County Health Department. Hand, Foot and Mouth Disease Fact Sheet The virus can stay in saliva and mucus for about 2 to 3 weeks and in stool for up to 11 weeks.25Sarpy County Health Department. Hand, Foot and Mouth Disease Fact Sheet Children with severe enterovirus 71 illness tend to shed it in stool longer, up to 10 weeks in one study.26PubMed. Intestinal detoxification time of hand-foot-and-mouth disease in children with EV71 infection and the related factors Careful handwashing after diaper changes therefore matters long after the rash fades.

Spread is greatest in the first week, when the child is sickest, and gradually falls afterward. Some infected people have no symptoms at all and can still pass it on, which is one reason it moves so easily through daycares.

For the same reason, a test can’t clear a child to go back. It can detect leftover virus in stool or saliva for weeks, so a positive result wouldn’t mean your child is still ill or needs to stay home. Waiting for a negative would keep a healthy child out of daycare for weeks, longer than anyone requires.

Most programs let children return once the fever is gone and they feel well. Keeping a child home until stool shedding stops isn’t practical or required. Check your daycare’s own policy, since some ask that blisters be dried.

At home, a few habits cut spread:

  • Wash hands with soap after diapers and before food.
  • Clean toys and surfaces with a bleach-based cleaner.
  • Don’t share cups, utensils or towels.
  • Avoid popping blisters, whose fluid carries the virus.