It's normal for a child's gas to be at least slightly smelly. But abnormally foul-smelling gas is usually related to constipation or something the child ate.

Children pass gas just as adults do, and it's normal for this gas to be at least slightly smelly. Truly foul-smelling gas is not as common, and if it occurs, it's usually related to constipation or something the child ate. Odorous gas may also be related to poor digestion or other medical conditions, so if this is an ongoing problem, speak to a pediatrician.

Why Does Gas Smell?

While some gas comes from swallowed air, most intestinal gas is a byproduct of digestion, and is formed when gut bacteria break down sugars and other carbohydrates in the colon.

The average person passes gas up to 21 times each day 2. Some of this gas is smelly, while most gas is barely noticeable. In a healthy child, the odor from gas is connected to the child's unique composition of gut bacteria, and also related to the specific foods consumed.

For instance, sulfur compounds found in a variety of foods including meat, nuts, dried fruits and cruciferous vegetables such as broccoli and cabbage give gas that rotten egg smell 2. Also, gas odor is influenced by the length of time the stool was in the gut. This is why a child who is constipated can have more smelly gas compared to a child who has daily, soft bowel movements.

Normal Stinky Gas

Some foul-smelling gas is to be expected in the average child, and sometimes this is related to constipation.

Children should also drink plenty of fluids and get active play time each day. Other foods can also cause smelly gas, so if the odor is an ongoing problem, keep a food and symptom diary to help determine which foods are causing the problem.

Common Causes of Flatulence in Children

Poor digestion or malabsorption of food is another reason for stinky gas. This occurs because gut bacteria have to spend more time processing these incompletely digested food particles, and as a result produce more gas. Intolerance to lactose, or the sugar in milk, can cause diarrhea, intestinal cramps and smelly gas.

Some children may not properly digest fructose, a natural sugar in fruit, so drinking apple juice or eating grapes, for instance, can lead to foul-smelling gas.

Potential Health Problems

Foul-smelling gas can be related to a medical condition which leads to improper digestion and absorption of certain food components 5. Celiac disease causes an immune reaction to gluten, found in wheat, barley and rye, and exposure to gluten leads to gut changes which include malabsorption.

Cystic fibrosis is a genetic disease which most notably impacts lung health, but can also cause poor nutrient absorption. Other conditions that can lead to excessive, foul-smelling gas because of improper digestion or absorption include Crohn disease, ulcerative colitis or pancreatitis.

Another temporary cause of foul-smelling gas is intestinal infections, such as food-borne illness or giardiasis, a water-borne illness caused fecal-contaminated water.

When to See a Pediatrician

If your child has diarrhea or if you suspect your child has an intestinal infection, she may require prompt medical attention to avoid dehydration. Also seek medical attention if your child has persistent foul-smelling gas, to evaluate if a food intolerance or medical condition is to blame.

Reviewed by Kay Peck, MPH RD