目的：探讨纯母乳喂养婴儿少量便血的原因。方法：研究对象为75例以少量便血为症状的纯母乳喂养婴儿，记录便血症状出现的年龄、伴随症状及实验室检查（血常规、大便常规、肝功能、大便培养、结肠镜及肠黏膜活检等）的结果。75例患儿的母亲均被指导进行膳食回避，即去除饮食中的动物及植物蛋白类食物4周，观察便血症状改善情况。结果：患儿出现便血症状的平均年龄为7.4周，最常见的伴随症状是腹泻（71%），实验室检查中以轻度贫血最多见（60%），大便常规可见红、白细胞，但大便培养均为阴性。结肠镜检查提示结肠炎，20例患儿行肠黏膜活检提示嗜酸性粒细胞增多。母亲去除蛋白饮食后的72~96 h，患儿肉眼可见的便血消失。结论：纯母乳喂养的婴儿可因对母亲摄入的蛋白过敏而出现便血。

OBJECTIVE: To investigate the causes of haematochezia in exclusively breast fed infants. METHODS: Seventy-five babies presenting with haematochezia were enrolled. These babies were exclusively breast fed. The age of haematochezia occurrence, concomitant symptoms and laboratory findings (including routine blood test, routine stool test, liver function, stool culture, colonoscopy and histological examination) were recorded. The mothers of the 75 babies were given a diet without animal and floristic proteins for four weeks. The symptoms of haematochzia in the babies were observed after maternal protein-free diets. RESULTS: Haematochezia occurred at an average age of 7.4 weeks. Diarrhea was the most common concomitant symptom (71%). The laboratory testing showed that mild anaemia was the most common (60%). Red cells and white cells were found in the routine stool test. Stool culture was negative. Colonitis was proved through colonoscopy. Twenty babies underwent histological examinations and eosinophilia was noted. Gross hematochezia disappeared 72-96 hrs after maternal protein-free diets. CONCLUSIONS: Exclusively breast fed infants may be sensitive to protein taken by their mothers and may appear with haematochazia.