In this randomized, single-blind clinical trial, infants younger than year with allergy to cow's milk protein referred to pediatric gastroenterology clinic of Bouali Sina Hospital of Sari are evaluated. In case of consuming probiotics and prebiotics within 2 months and receiving antibiotics within 2 weeks patients are excluded. Patients are randomly divided into two intervention and control groups with table of random numbers. Limitation of dairy cattle consumption for mother and infants are applied. For the intervention group, in addition to diet protocol, one sachet Protexin probiotic made by Health care co. is administered daily for 4 weeks and the control group receives the same package containing Aptamil Pepti Junior formula one sachet per day for 4 weeks. At the beginning of the study, stool cultured and analysis and fecal calprotectin are performed for all patients and then at second, 4th, 8th, 12th and 16th week, WBC and RBC level and occult blood and fecal calprotectin are measured. At 4th and 16th week, stool culture is done to determine the intestinal flora. During the first 16 weeks of the treatment, the number of stools per week, mucoid stools per week, number of stool bleeding in week, pain in week are recorded and compared between two groups.