Immediate systemic allergic reaction in an infant to fish allergen ingested through breast milk.

This is a rare case report of systemic allergic reaction to fish allergen ingested through breast milk. Mother ate raw fish more than 3 times a week. Her consumption of fish was associated with urticaria and wheeze in an infant via breast-feeding. Fish-specific IgE antibodies were detected by skin prick test but not by in vitro IgE test. This case demonstrates that fish protein ingested by mother can cause an immediate systemic allergic reaction in offspring through breast-feeding. Although fish intake is generally recommended for prevention of allergy, one should be aware that frequent intake of fish by a lactating mother may sensitize the baby and induce an allergic reaction through breast-feeding.