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Gastroenteritis (Stomach Flu)

Reviewed by: Mary L. Gavin, MD
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What Is Gastroenteritis?

Gastroenteritis, often called the stomach flu, is a common illness that causes nausea, vomiting, diarrhea, and belly cramps. It usually lasts a few days and isn't serious. Most kids get better at home by resting and drinking plenty of liquids.

What Causes Gastroenteritis?

Gastroenteritis (gass-troh-en-teh-RYE-tis) happens when germs (viruses, bacteria, or parasites) infect the stomach or intestines, causing inflammation.

In kids, viruses are the most common cause of gastroenteritis. Rotavirus causes many cases of stomach flu in children, but the rotavirus vaccine can help prevent them.

Many of the germs that cause gastroenteritis spread easily. So someone can get sick if they:

  • Touch something contaminated and then touch food or their mouth.
  • Share food or drinks with someone who is sick.
  • Live with someone who’s infected, even if that person isn’t sick.

What Are the Signs & Symptoms of Gastroenteritis?

The most common signs of gastroenteritis are vomiting and diarrhea. Many children also have a fever.

When kids have diarrhea or vomiting, they lose lots of fluid in their poop or vomit. This can lead to dehydration (not having enough water in the body). If that happens, the body can have trouble working as it should.

How Is Gastroenteritis Diagnosed?

Doctors usually can tell if someone has stomach flu by hearing about the symptoms. Usually, no tests are needed. If a child is very sick or has blood or mucus in the poop, doctors might order a stool (poop) test, urine (pee) test, or blood test to check for dehydration and to see what’s causing it.

How Is Gastroenteritis Treated?

There is no specific treatment for gastroenteritis, and most kids can be treated at home. Keep your child hydrated by offering plenty of liquids. Kids with more severe dehydration may need treatment in the ER or hospital.

Mild dehydration is treated with oral (by mouth) rehydration. This usually includes giving oral rehydration solution (such as Pedialyte, Enfalyte, or a store brand). It has the right amounts of water, sugar, and salt to help with dehydration. You can buy it without a prescription at drugstores or supermarkets. If you can’t get oral rehydration solution, talk to your doctor.

If your child has mild dehydration and your doctor says it’s OK to start treatment at home:

  • Give your child an oral electrolyte solution as often as possible. If your child throws up, start with small sips, about 1 or 2 teaspoons every few minutes.
  • Babies can continue to breastfeed or take formula as long as they are not throwing up repeatedly.
  • Don't give babies plain water instead of oral rehydration solution. It doesn't have the right nutrients for babies with dehydration.
  • Older children can have frozen electrolyte popsicles.
  • Do not give your child full-strength juice (undiluted), soda, or sports drinks. These have a lot of sugar, which can make diarrhea worse.

When your child stops vomiting, you can offer small amounts of solid foods, such as toast, crackers, rice, or mashed potatoes. Yogurt, fruits, vegetables, and lean meat, like chicken, are also OK. 

A child who isn’t throwing up can eat a regular diet, if they feel up to it. It may take time for them to feel like eating. There's no need to avoid dairy unless it makes the vomiting or diarrhea worse. Avoid fatty foods, which can make diarrhea worse.

To help your child feel better, let your child rest as needed. You can give medicine for fever or pain, like acetaminophen or ibuprofen (do not give ibuprofen to babies under 6 months old), if your doctor says it’s OK. Follow the package directions for how much medicine to give and how often. Don't give aspirin to your child or teen. It's linked to a rare but serious illness called Reye syndrome.

Don't give medicines for diarrhea or vomiting unless your doctor tells you to.

Keep your child out of school or childcare until 24 hours without vomiting or fever and diarrhea has improved. Your child also should stay out of swimming pools until all symptoms have stopped.

When Should I Call the Doctor?

Call the doctor if your child:

  • can’t drink for several hours
  • is peeing less often (more than 4–6 hours for babies and 6-8 hours for older children)
  • has signs of dehydration, such as crying with few or no tears, having a dry mouth or cracked lips, feeling dizzy or lightheaded, acting very sleepy or less alert
  • has a high fever
  • has blood in their poop or vomit
  • is vomiting for more than 24 hours or the diarrhea doesn’t get better after several days

Can Gastroenteritis Be Prevented?

Germs that cause gastroenteritis are contagious. That best way to avoid the illness is to keep the germs from spreading:

  • Teach all family members to wash their hands well and often. They should wash for at least 20 seconds with soap and water. This is especially important after using the bathroom and before preparing or eating food.
  • Clean tabletops, doorknobs, and other surfaces that get touched a lot with a cleaner that kills viruses.
  • Follow food safety guidelines to prevent bacteria and viruses from getting into food and drinks (food poisoning).
  • Make sure your kids get all recommended immunizations on time.
Reviewed by: Mary L. Gavin, MD
Date reviewed: September 2021