New parents know what colic is, but clinically, colic is defined as excessive crying in an otherwise well infant. More specifically, when an infant who is less than 3 months old, cries for more than three hours a day, more than three days in a week, he or she is labeled as colicky.

Chances are his parents are exhausted, frustrated, depressed, and feeling insecure about their parenting skills. They have probably tried walking their baby around, swaddling him with a blanket, changing her formula if she isn't breastfeeding, changing his mother's diet if he is breastfeeding.

Parents may try stimulating him, keeping her in a quiet environment, picking him up, and letting her cry it out by herself. Well−meaning friends and relatives will have offered their diagnoses: stomachache, gas, boredom, tension, and a host of other causes.

Colicky babies have a greater number of hydrogen-producing bacteria that in turn may cause discomfort to the infant.

Hopefully, his or her parents have taken him to the doctor to be carefully examined for treatable causes of discomfort, including ear infection, hair or thread wrapped around a finger or toe, rectal fissure or irritated diaper rash and others. And in spite of it all, the baby is still crying.

Since living with a colicky infant causes so much parental anguish and family stress, there are many theories about what causes it, and its causes and treatment have been the subject of extensive and diverse research. High strung babies, depressed parents, immature digestive systems, intolerance to mother's diet in breast feeding infants, intolerance to cow's milk formula, overstimulation, swallowed air, and stress are among the many explanations. It is likely that one explanation will not fit all infants.

A new study published in the July issue of the Journal of Pediatrics provides evidence that bacteria may play a major role in causing the discomfort of colicky babies. Using methods from studies on older patients with diagnosed gastrointestinal problems such as celiac disease and irritable bowel syndrome, they used specific laboratory techniques to identify signs of inflammation of the gastrointestinal tract and to explore differences in the types of bacteria found in the digestive system of colicky vs. non−colicky infants.

By measuring a compound that identifies inflammation in the intestines of children with inflammatory bowel syndrome, researchers found that colicky infants had twice as much evidence of inflammation as their non− colicky peers. Common causes of inflammation of the bowel include food allergy, intestinal infection, and abnormal types of bacteria in the bowel. They felt that food allergy could be ruled out by the lack of other signs of allergy and the fact that formula changes didn't improve colic. They postulated that colicky infants might have excessive growth of bacteria in their small bowels, or excessive fermentation of carbohydrate in the colon.

Everyone has bacteria in their gastrointestinal tracts that act on the undigested food as it is passing through. Some types of bacteria are more likely to produce gas by causing fermentation of incompletely digested carbohydrates in the colon. This is similar to individuals with lactose intolerance, who have excess gas and abdominal discomfort from fermentation of undigested lactose (a milk−sugar) in the large bowel. Researchers found evidence that colicky babies have a greater number of hydrogen−producing bacteria that in turn may cause discomfort to the infant.

Adding to the evidence for abnormalities of colonic bacteria in colicky infants, the researchers also found that colicky infants had fewer different types of bacteria in their digestive tracts than infants without colic. This has been found in older patients with celiac disease who cannot digest gluten properly and have abdominal pain and decreased ability to absorb nutrients from digested food.

The gastrointestinal differences found in colicky infants could be both cause and effect. Changes in intestinal bacteria could cause inflammation of the bowel by changing the acidity and liquid content of fecal material passing through the bowel. Alternatively, the presence of inflammatory compounds in the bowel could influence the types of bacteria that grow in the bowel. Nonetheless, the researchers found clear evidence of gastrointestinal changes in infants with colic which had been thought to be based on temperament and environment, more than physical abnormalities. Their findings pave the way for new investigations into approaches to treat colic. This group of researchers plans to study the impact of probiotics, the "good" bacteria found in yoghurt, on colicky babies.

Parents with colicky infants often benefit from having a trusted babysitter stay with their infant so they can get a break from the nerve−wracking effect of constant crying. If you are the parent of a colicky baby, consulting regularly with your baby's doctor for reassurance and advice and to rule out physical causes of pain and discomfort to the infant. Although it seems endless, colic lasts just a few months and parents move on to other, perhaps quieter, challenges.