Colic is a state of excessive crying seen in infants, typically during the late afternoon or early evening. From 15% to 20% of infants develop colic, and it seems to be more common in firstborns and in boys than in later-born infants and in girls. Colic is not a disease or syndrome caused by bacteria or viruses. It is seen in otherwise healthy infants and can begin as early as 2 weeks of age. It is self-limited, only rarely lasting until the infant is 6 months old.

No cause has been proven for this disorder, but theories include those listed below.

• Stage in the development of an immature central nervous system or digestive system
• Response to emotional and family stress—need for comfort
• Reflection of differences in infant temperament and physiology
• Intolerance to foods in mother's diet, specifically, dairy products, caffeine, or gas-producing foods
• Introducing food into infant's diet too early
• Over-stimulation or under-stimulation of infant
• Second-hand smoke
• Antibiotics given at birth or to mother during labour

• Inconsolable crying that lasts more than three hours for three or more days a week in a healthy infant 2 weeks to 3 months of age
• Crying accompanied by vigorous kicking, pulling the legs up tightly to the body, and making tight fists
• May have swollen or distended stomach, burp, or pass gas often
• Infant appears to be in pain
• Arched back and clenched fists
• Frequent vomiting after feeding