What causes oral thrush in babies?

What Causes Oral Thrush in Babies

Oral thrush in babies is caused by the yeast fungus Candida albicans, which infects the mucous membranes of the mouth, tongue, palate, cheeks, and lips. 1

Primary Causative Organism

• Candida albicans is the most frequent species causing oral candidiasis in infants, accounting for the majority of cases 2
• Candida parapsilosis and other Candida species occur less commonly in the infant population 2, 3

Key Risk Factors and Transmission Routes

Maternal Transmission

• Infants acquire Candida primarily from their mothers during or after birth 4, 5
• Maternal breast candidiasis serves as a continuous source of reinfection, requiring treatment of both mother and infant to prevent persistent thrush 5
• Maternal mastitis and antibiotic use are significantly associated with infant thrush development 3

Prematurity and Medical Interventions (for invasive candidiasis)

• Prematurity is the primary risk factor for serious neonatal candidiasis, particularly in extremely low-birth-weight infants (<1000g) 2
• Central vascular catheterization, broad-spectrum antibiotics (especially third-generation cephalosporins and carbapenems), parenteral nutrition, and endotracheal intubation increase susceptibility 2
• Abdominal surgery and necrotizing enterocolitis are additional risk factors in the NICU setting 2

Immunodeficiency States

• Various immunodeficiency conditions increase susceptibility to fungal infections, though persistent thrush without other immunodeficiency signs is uncommon 6

Important Clinical Distinctions

Mode of Delivery

• Cesarean delivery does NOT increase the risk of thrush development compared to vaginal delivery 7
• This finding suggests that delivery mode is not a significant contributing factor 7

Diagnostic Considerations

• Clinical diagnosis is typically based on thick, yellowish-white patches on oral mucosa 3
• Interestingly, recent research found that C. albicans was not detected in some infants with clinical thrush, suggesting the etiology of white patches may be more complex than traditionally understood 3

Common Pitfalls

• Do not assume all white oral patches are candidiasis—the etiology may remain unclear in some cases 3
• Always evaluate and treat maternal breast candidiasis concurrently to prevent reinfection cycles 5
• Avoid treating with acidic liquids (lingonberry or lemon juice), as this approach is not efficient 3