Gastroenteritis

Symptoms

• Diarrhea (more frequent and looser stools than usual)
• Nausea or vomiting
• Reduced appetite
• Fever and stomach ache (sometimes)
• Signs of dehydration (sometimes)

• Is under 3 months old
• Vomits more than 6 or 7 times a day
• Refuses to drink or throws up immediately after drinking
• Has a dry tongue
• Seems to be urinating less
• Has stools with traces of blood
• Has a hard, tender belly or bouts of severe abdominal pain

What is gastroenteritis?

Gastroenteritis (also known as stomach flu) is an inflammation of the digestive system usually caused by a virus.

Its main complication is dehydration. This can develop quickly, especially in children under 2.

Signs of dehydration

Dehydration is the loss of fluids (made up of water and minerals) that are essential for the body to function properly.

Signs of mild dehydration

• Decreased urine, saliva, and tears when crying
• Darker urine
• Dry skin, mouth, and tongue

Signs of severe dehydration

• Significant decrease in urine (no urine for more than 6 to 8 hours for an infant, or more than 8 to 10 hours for a child aged 2 or older)
• Dark, sunken eyes
• Drowsiness or disorientation
• Fever
• General weakness
• Sunken fontanelle (soft spot) on an infant

Treatment

Anti-nausea, anti-vomiting, and anti-diarrheal medications are not recommended to treat gastroenteritis. Some of these medications may even make the illness worse and cause significant side effects in children.

Antibiotics are also ineffective for viral gastroenteritis. In some cases, the doctor may order a stool test to determine the nature of the infection. If it is caused by a bacterium or parasite rather than a virus, the doctor will likely prescribe an antibiotic or antiparasitic.

The doctor’s main concern when treating gastroenteritis is making sure the child does not become dehydrated. If your child is severely dehydrated, they should be seen by a doctor as soon as possible.

In cases of severe or prolonged gastroenteritis, a child may develop a temporary lactase deficiency. The doctor may recommend switching to lactose-free milk.

How to prevent dehydration

If your child is vomiting or has diarrhea, it’s important to make sure they drink enough fluids to prevent dehydration.

If your child is vomiting

Have them drink an electrolyte solution (e.g., Pedialyte^®, Gastrolyte^®) for 24 to 48 hours. These products are also available as freezer pops.

Don’t give your child “sports drinks” like Gatorade®. They don’t contain the right balance of water, sugar, and salt, and can make your child’s symptoms worse. Soft drinks (even if flat), fruit juices, and broths should all be avoided for the same reason.

If your baby is breastfeeding, breastfeed more often but for shorter periods. You can also alternate between breastfeeding and bottle-feeding with an electrolyte solution. This can help them rehydrate more quickly, especially if they aren’t tolerating breast milk.

If your baby is only bottle-feeding, continue with their usual formula, but feed more often and in smaller amounts. Alternate the usual formula with bottles of electrolyte solution. Do not water down the formula.

To avoid causing more nausea and vomiting, give your child small amounts of liquid at very short intervals. The recommended quantities vary by age:

• Under 6 months: 30 to 90 ml (1 to 3 oz.) per hour, or about 5 ml (1 tsp) every 5 minutes. Gradually increase this amount and lengthen the intervals between feeds according to your baby’s tolerance.
• 6 months to 2 years: 90 to 125 ml (3 to 4 oz.) per hour, or about 10 ml (2 tsp) every 5 minutes. Gradually increase this quantity by lengthening the intervals according to your child’s tolerance.
• Over 2 years old: 125 to 250 ml (4 to 8 oz.) per hour, or about 15 ml (1 tbsp) every 5 minutes. Gradually increase this quantity by lengthening the intervals according to your child’s tolerance.

Feeding a child who is vomiting or has vomited

If your child is no longer vomiting or is vomiting very little (with or without diarrhea), or if they only have diarrhea:

• If your baby is only breastfeeding or bottle-feeding, return to their usual feeding schedule.
• If your child is older, resume their normal diet gradually as their vomiting subsides. Eating helps the intestines heal, so your child should start eating again as soon as possible. If they don’t eat, the diarrhea may persist longer, and they won’t be getting adequate calories, nutrients, minerals, or vitamins. For the same reasons, if your child has diarrhea without vomiting, they should stick to their usual diet as much as possible.
• Give your child small amounts of food several times a day (5 or 6 small meals) to start.
• Serve them whatever they feel like eating, including dairy products.
• Avoid fatty or sugary foods (chips, fries, pastries, cold cuts, ice cream, juice, sodas, sugary cereals, dried fruit, fruit in syrup, candy, chocolate, etc.). Store-bought broths and soups (in packets or cans) should also be avoided since they are too salty.

Prevention

The vaccine that protects against rotavirus gastroenteritis, the most common form of gastroenteritis in infants, is now part of the vaccination schedule. Two doses are needed to ensure your child is well protected: the first at 2 months and the second at 4 months. The vaccine comes in liquid form and is administered orally.

Children can still get gastroenteritis even if they’ve been vaccinated. This is because the vaccine protects only against rotavirus, and other viruses can also cause the illness.

Limiting the spread

Gastroenteritis is highly contagious. It spreads quickly among young children, as they are often in groups at daycare and wear diapers.

Here are some ways to limit the spread of the virus:

• Clean and disinfect objects and areas that have been in contact with your child’s vomit or feces, including the toilet.
• Make sure your child washes their hands thoroughly and frequently, especially after using the toilet and before eating. If they are too young to do this on their own, do it for them.
• Make sure that everyone who comes into contact with your child also washes their hands. Wash your hands after taking them to the toilet or changing their diaper, before feeding them or giving them medicine, etc.
• As much as possible, avoid direct contact between your baby and any older children who have diarrhea along with signs of a respiratory infection. This is even more important for infants under 3 months old. The gastroenteritis virus can also spread through respiratory droplets.

Preventing bacterial gastroenteritis

Most cases of gastroenteritis are caused by viruses, but your child may develop bacterial gastroenteritis—caused by bacteria like salmonella—after consuming contaminated food or water, or through contact with a person or animal whose feces contain bacteria.

To reduce the risk of bacterial gastroenteritis:

• Avoid drinking water from streams or springs unless you’re sure it’s safe.
• Follow basic hygiene rules in the kitchen:
     – Before preparing fruits and vegetables, peel them or rinse them under running water, especially if they will be eaten raw.
     – Disinfect surfaces that have come into contact with raw meat or fish.
     – Make sure meat is thoroughly cooked before eating.
• Keep pet bowls and litter boxes away from areas where food is prepared or eaten. Reptiles, turtles, and lizards can carry bacteria that cause diarrhea.
• When travelling to tropical countries, drink only bottled water. Peel fruit yourself and avoid foods that may have been washed in tap water. Avoid food sold at street stalls.

Scientific review: Dr. Isabelle Viel-Thériault, pediatrician and infectiologist at CHU de Québec Research and copywriting:The Naître et grandir team Updated: April 2025

Photo: Adobe Stock/ulza