Infantile colic is characterized by excessive crying (defined as crying that last at least 3 hours a day, for 3 days a week, for at least 3 weeks) in an otherwise healthy infant. The crying typically starts in the first few weeks of life and ends by 4-5 months of age. The condition is usually self-limited, with no long-term adverse effects; however, it may be very distressing to parents, hence, any safe and effective treatment would be desirable. Recently, it has been suggested that probiotics may offer some benefit.This is based on the results of one open randomized controlled trial. In this trial, 83 breast-fed infants with colic defined as >3 hours of crying on >3 days/week were randomly allocated to receive Lactobacillus reuteri DSM 17938 (108 colony-forming units, once daily 30 minutes after feeding) or simethicone (60 mg/day as 15 drops twice a day after feeding) for 28 days. Mothers followed a cow's milk free diet. By day 28 after randomization, mothers of infants in the probiotic group were significantly more likely than mothers of infants in the simethicone group to report a reduction from baseline in average crying time to less than 3 hours per day (95% vs. 7%). In addition, median crying times were significantly shorter in the probiotic group than in the simethicone group. No adverse effects of L. reuteri were reported.

Although the mechanism of action of L. reuteri for treating infantile colic has not been elucidated yet, the findings are very promising. However, there are some methodological limitations to the study, including no allocation concealment, no blinding, and no intention-to-treat analysis; these may result in selection, performance, and/or attrition biases and, eventually, invalidate the results. Another limitation of the study is the lack of a true placebo group. Given these consideration a new study is proposed that is aiming to overcome these limitations.

Eligible infants will be randomly assigned to receive either L. reuteri 108 CFU per day or placebo. Both the active treatment and placebo will be taken orally, 1 times daily, for 21 days.

All infants are eligible for screening. If a patient appears to meet the criteria for enrollment and express interest in the study, cow's milk elimination diet will be prescribed for 1 week to a breastfeeding mother (and to an infant, in case of formula fed infants). Care givers will be asked to record for 1 week symptoms of colic. Children fulfilling inclusion criteria will be asked to participate in the study.

Inclusion Criteria:

• Full-term infants age <5 months
• Infantile colic (>3 hours of crying on >3 days in the week) within 7 days prior to enrollment
• Exclusive or predominant (>50%) breastfeeding
• Informed consent

Exclusion Criteria:

• Acute or chronic illness
• Gastrointestinal disorders
• Use of any antibiotics and/or probiotic pharmaceutical products within 7 days prior to the study.