What Causes Diarrhea in Breastfed Infants?

Generally, diarrhea in breastfed infants may result from factors such as overfeeding, lactose intolerance, allergy, intestinal dysbiosis, or enteritis. It is recommended to seek prompt medical evaluation to identify the underlying cause and initiate targeted treatment. A detailed analysis follows:

1. Overfeeding

Infants have relatively small gastric capacities. Excessive breast milk supply, rapid feeding, or large single feed volumes may overwhelm the infant’s digestive capacity, leading to indigestion and subsequent diarrhea. Stools are typically soft or semi-formed and may contain undigested curds (“milk curds”). To prevent this, caregivers should regulate feeding volume and pace—opting for smaller, more frequent feedings—to allow adequate time for digestion and absorption.

2. Lactose Intolerance

Lactose intolerance arises when infants lack sufficient lactase enzyme to break down lactose in breast milk. Undigested lactose ferments in the intestine, producing excess gas and acidic metabolites that accelerate intestinal motility, resulting in diarrhea. Stools are typically yellow or yellow-green, watery, frothy, and emit a sour odor. Under medical guidance, supplemental lactase enzyme may be administered to aid lactose digestion.

3. Allergy

In some infants, the immature immune system mistakenly identifies cow’s milk protein (transmitted via maternal diet into breast milk) as a foreign antigen, triggering an allergic reaction. This can damage the intestinal mucosa, causing symptoms such as diarrhea and even bloody stools. Mothers are advised to eliminate cow’s milk and dairy products from their diet to reduce allergen exposure in breast milk and thereby alleviate the infant’s allergic symptoms.

4. Intestinal Dysbiosis

Infants’ gut microbiota are still developing and thus vulnerable to disruption—for example, by inappropriate antibiotic use or concurrent illness. Such disturbances may deplete beneficial bacteria while allowing pathogenic bacteria to proliferate and produce toxins, irritating the intestinal mucosa and precipitating diarrhea. Under physician supervision, probiotic agents—such as triple-strain bifidobacterial powder or quadruple-strain bifidobacterial tablets—may be prescribed to restore microbial balance and improve the intestinal microenvironment.

5. Enteritis

Infection of the intestine by bacterial, viral, or fungal pathogens induces inflammation, impairing normal intestinal absorption and secretion functions. This leads to increased intestinal fluid secretion, frequent loose stools, and often accompanying symptoms such as vomiting and fever. Symptomatic management may include medications such as smectite powder, lactobacillus tablets, or roxithromycin granules, as prescribed by a healthcare provider.

In daily life, maintaining healthy habits is essential: avoid spicy or irritating foods—including Sichuan pepper, chili peppers, and garlic—as these may hinder recovery.