Managing Lactose Intolerance in Infants: Diagnosis, Dietary Adjustments, and Formula Options

Lactose intolerance in infants is usually secondary (post-infectious, cow's milk protein allergy) rather than primary (congenital lactase deficiency is rare).

Diagnostic Approach

• Clinical: Watery, frothy, acidic stools; perianal excoriation; bloating, irritability after feeds.
• Trial of lactose-free diet: Resolution in 48–72 hours supports diagnosis.
• Tests: Reducing substances in stool (Clinitest), fecal pH <5.5, hydrogen breath test (older infants), genetic testing (congenital).

Management

1. Breastfed infants: Mother continues breastfeeding; lactose in breast milk is constant. If secondary to CMPA, maternal dairy elimination for 2–4 weeks.
2. Formula-fed: Switch to lactose-free formula (soy-based if >6 mo, or extensively hydrolyzed/amino acid-based if CMPA suspected).
3. Gradual reintroduction: After 2–4 weeks, reintroduce lactose-containing formula/breast milk to assess tolerance recovery.
4. Probiotics: L. reuteri, B. lactis may shorten duration of secondary lactase deficiency.

Key Distinction: Lactose Intolerance vs. Cow's Milk Protein Allergy (CMPA)

CMPA involves immune reaction (IgE/non-IgE) to casein/whey—requires strict dairy elimination. Lactose intolerance is enzymatic (lactase deficiency). They often coexist post-gastroenteritis.

Pediatrician guidance ensures adequate nutrition (calcium, vitamin D) during dietary modifications.