Feeding time should be comforting, but for some babies, it leads to gas, bloating, and fussiness. This could be a sign of lactose intolerance, caused by a lack or absence of lactase. When there's not enough of this enzyme, undigested lactose stays in the gut, causing discomfort.

Lactose intolerance is more common in older children and adults, but babies can experience it too. It’s usually temporary and triggered by gut infections like rotavirus. Knowing what to watch out for can help parents manage symptoms and keep their babies comfortable.

In this article, we will discuss the signs of lactose intolerance in babies, what causes it, and how to manage it effectively.

What Is Lactose Intolerance?

Lactose intolerance happens when the body doesn't produce enough lactase, the enzyme needed to break down lactose, the sugar found in milk. Gut infections or premature birth often cause temporary lactose intolerance in babies.

In rare cases, there is a congenital lactase deficiency, where lactase is absent from birth. This condition can occur in breastfed babies, but it's more common in formula-fed babies.

Lactose intolerance can also be genetic, and in some cases, it's inherited (it runs in families). This is especially true for congenital lactase deficiency, a rare genetic condition where babies are born with little to no lactase, the enzyme needed to digest lactose.

Lactose Intolerance Symptoms In Babies

Babies with lactose intolerance may show a variety of symptoms, usually appearing 30 minutes to 2 hours after feeding. Some of the most common signs include:

• Diarrhea – Stools may be watery, frothy, and bulkier than usual.

• Bloating and gas – Excessive gas can cause discomfort and irritability.

• Stomach pain – Babies may clench their fists, arch their back, or kick their legs in discomfort.

• Crying and fussiness – Digestive discomfort can make babies more irritable, especially after feeding.

• Feeding difficulties – Frequent pauses during feeding or reluctance to feed.

• Poor weight gain – Some babies struggle to gain weight due to difficulty digesting lactose.

• Diaper rash – Frequent diarrhea may lead to redness and skin irritation.

While these symptoms can indicate lactose intolerance, they can also be linked to other conditions, such as milk allergies or general digestive sensitivities.

How is Lactose Intolerance Diagnosed?

If you notice recurring symptoms, especially after illnesses like rotavirus, a pediatrician might recommend some diagnostic tests. A stool test can help determine if lactose intolerance is the cause. They might also suggest an elimination diet trial, where dairy products are removed from your baby's diet for a short period to see if symptoms improve.

If a milk allergy is suspected, additional allergy tests may be needed to help differentiate between the two conditions.

Treating Lactose Intolerance in Babies

Managing lactose intolerance in babies often involves dietary adjustments. These changes can include:

For formula-fed babies: Lactose-free formula may be recommended.
For breastfeeding babies: Breastfeeding can usually continue unless the intolerance is severe. In such cases, switching to lactose-free breast milk (if available) or formula may be necessary.

When introducing solids:

• Avoid high-lactose foods like yogurt and soft cheeses.

• Hard cheeses (e.g., cheddar) are often better tolerated due to their lower lactose content.

• Beverages: Steer clear of sweetened drinks like juice or cordial.

When it’s time to reintroduce lactose, do so gradually. Start with small amounts and increase the intake slowly over 5–7 days to allow the baby’s digestive system to adjust. This step-by-step process can help babies transition back to regular breast milk or formula without causing discomfort.

Managing Lactose Intolerance in Babies

Lactose intolerance symptoms in babies are rare and can be tough to deal with, but they’re usually manageable with the right adjustments. Signs like diarrhea, stomach discomfort, and feeding issues are common, so recognizing them early can help parents take the necessary steps to keep their baby healthy and comfortable. 

If you suspect that your baby may be suffering from lactose intolerance, make sure to consult with a pediatrician for a proper diagnosis and advice. With the right care, most babies can thrive, even with lactose intolerance.