Lactose Sensitivity in Babies: What Doctors Are Learning Baby lactose problems? Discover what experts know about the different types of lactose issues.

There are four different types of lactase deficiency—a lack of the enzyme that breaks down lactose into simple sugars that can then be used by the body, meaning that lactose may pass into the large intestine without being properly broken down—that may lead to intestinal discomfort.

Primary Lactose Intolerance

This type mainly occurs with aging. Lactose intolerance is uncommon in babies—most babies have normal quantities of lactase (the enzyme needed to break down lactose). However, as kids grow and their diet moves away from exclusively milk products, they sometimes develop primary lactose intolerance. This tendency may be inherited from the parents, and it often varies according to the baby’s ethnic or family background.

Secondary Lactose Intolerance

If your baby had an injury to her small intestine or has a digestive issue—like inflammatory bowel or celiac disease—lactose intolerance can result. However, the good news is that once the underlying issue is addressed, your baby’s lactose intolerance may eventually go away.

Developmental Lactase Deficiency

This issue primarily affects preemies due to insufficient lactase levels. The enzyme lactase increases in the digestive tract in the third prenatal trimester, so babies born early might not have had the chance for their digestive tract to develop properly. The good news is that this issue may last only a short time.

Congenital Lactose Intolerance

This extremely rare issue, in which a baby is born with a complete lack of lactase, is inherited through a gene from both mother and father. Since the baby is completely intolerant of the lactose in breast milk, it's important to talk to the baby's doctor about an infant formula suitable for someone with lactose intolerance. 

Ask Your Pediatrician

If you think your baby may have a lactose sensitivity, talk to your pediatrician about it. Read “Lactose Sensitivity in Babies: Questions to Ask Your Pediatrician” for advice on what to ask. And for more information about issues, read “Help for Baby’s Lactose Sensitivity: Everyday Tips.”