Can a breastfeeding mother's diet cause allergies in her baby?

In rare cases, proteins from foods a mother eats (especially cow's milk, eggs, or peanuts) can pass through breast milk and cause reactions in sensitive babies — symptoms include excessive fussiness, eczema flare-ups, bloody stools, or vomiting. However, most babies tolerate breast milk regardless of maternal diet. Do not eliminate foods preemptively without medical guidance, as unnecessary restrictions can affect your nutrition. Talk to your pediatrician before making dietary changes.