The term colic is used to describe intense or excessive crying or fussiness in an otherwise healthy infant. This typically starts in the second or third week of life and resolves by three to four months (although it can persist longer). A variety of definitions of excessive crying have been used. Perhaps the most useful is Wessel's "rule of threes": more than three hours per day for more than three days per week for more than three weeks. The most common time of day seems to be early evening. In extreme cases the crying may occur throughout the day and night. Prospective studies have shown that colic is common. Dr. T.B. Brazleton, using crying diaries kept by parents, found that 35% of 6-week-old infants cried for more than three hours per day. Typically these infants cry longer, though not more frequently, than other infants and are more difficult to console.

The etiology of colic is unknown. The fact that it occurs in healthy babies, follows the crying pattern of normal infants and resolves without later sequelae has prompted its description as a disorder of development.

Colic occurs with equal frequency in breastfed and formula-fed infants. The question of milk intolerance as a possible cause of colic is frequently raised, and formula changes are a commonly tried intervention. Cow's milk protein sensitivity probably does cause colic in a small subgroup of infants. These infants may also experience weight loss, vomiting and diarrhea. With such a history, a trial of casein-hydrolyzed formula would be appropriate. The incidence of lactose or carbohydrate malabsorption does not appear to be different in patients with colic compared to those without.

Intestinal immaturity with delayed development of normal patterns of intestinal motor activity and resulting poor propulsion has been proposed as an etiology. Many infants with colic appear uncomfortable, draw their legs up and pass wind. This may be secondary to air swallowing with crying. Antispasmodics and antiflatulents have generally not been shown to help. There is evidence that one antispasmodic, dicylomine hydrochloride, may be effective; however, concern regarding respiratory distress and apnea preclude its use. Intestinal hormones may play a role in colic; this role is incompletely understood at this time, however.

At one time, colic was blamed on "overanxious mothers", but there is no scientific confirmation of this etiology. Certainly, prolonged crying in an infant can itself give rise to anxiety in parents.

In the evaluation of a patient with colic it is first essential to take a thorough history to rule out pathological causes of crying, inquire about feeding practices (including formula preparation and burping procedure) and soothing techniques. For an accurate description of duration of crying it is useful to have the mother keep a diary over a few days. A thorough physical examination must be performed to assess growth and development as well as rule out illness (particularly infection) or intestinal obstruction.

If no apparent cause is found for the crying it is first essential to relieve parental guilt and reassure parents that they do not cause the colic. Explaining the natural history of colic (frequency and duration) can be very helpful. Trials of soothing techniques (carrying the baby in a body carrier, car rides or automatic rockers) may be useful. Advising parents on obtaining relief - babysitting or even a weekend away - is often the best intervention. Finally, a trial of casein-hydrolyzed formula for the infant or a milk-free diet for the breastfeeding mother may be useful, particularly if additional symptoms suggesting food allergy are present.