The sugar lactose is found in all mammalian milks, including human breast milk and the cow's milk used as the base for most infant formulas. Someone with lactose intolerance cannot produce enough lactase, the enzyme that breaks down lactose in the small intestines. Most people with lactose intolerance develop the problem in late adolescence or adulthood and lactose intolerance in infants remains rare. Nonetheless, some babies develop temporary lactose intolerance that lasts only a short time.
Causes
Unlike a permanent lactose intolerance, a temporary lactose intolerance in infancy isn't something a baby is born with. Instead, a severe bout of diarrhea is usually to blame. Any illness or food sensitivity that causes irritation to the intestinal lining can lead to a breakdown in the cells that normally produce lactase. Parasitic infections and celiac disease are other potential causes of intestinal damage that can lead to temporary lactose intolerance.
Symptoms
A baby with lactose intolerance might develop green, frothy stools or diarrhea. He also will probably become extremely gassy due to the breakdown of lactose by bacteria in the colon. This can lead to irritability and crying. A baby over about 3 months of age can be tested for hydrogen in his breath, which can indicate the presence of a lactose intolerance. Babies younger than that naturally have high levels of respiratory hydrogen, so this test is unreliable.
Solution
If the lactose intolerance is mild, a breastfeeding mother may continue to nurse her child as long as the baby continues to grow properly. The healthy components in breast milk will help heal the intestines even though lactose is present in her milk. In severe cases, such as when the baby is losing weight or is formula-fed, the doctor might suggest switching to a soy-based formula while the infant's intestines heal. In most cases, temporary lactose intolerance resolves itself within about four weeks, although some infants take up to eight weeks to fully recover.
Considerations
A temporary lactose intolerance cannot be treated by reducing the dairy consumption of the breastfeeding mother, since breast milk contains its own lactose. However, since food allergies can cause intestinal damage and some babies are allergic to milk proteins that come through a mother's breast milk, it is possible to have both a milk allergy and temporary lactose intolerance in the same baby at the same time.
