Then there are the cries that seem to have no rational cause and don't respond to soothing for very long. This may mean a baby is venting at the end of a long day, but if the crying goes on for hours every day, at roughly the same time, several days a week, then you can feel justified in calling it colic. Some pediatricians use the Rule of Three to diagnose colic: crying for no apparent physical reason for three hours a day, three days a week, for three weeks. By this definition, one out of five babies has colic.

In spite of trying for more than fifty years, doctors haven't pinpointed the cause of colic. Historically, it is believed to be some kind of abdominal pain (the word colic is derived from kolon, which is Greek for large intestine), but even that's not certain.

Colic may be caused by an immature digestive system that spasms rather than uses smooth muscle contractions. Or it may be that certain babies just notice the workings of their digestive system more. Some researchers have suggested that it may be an allergic reaction to something in the mother's diet — cow's milk in particular. This theory is controversial, as colicky babies don't have any symptoms of the stomach problems associated with such an allergy, like diarrhea or vomiting. Colic may be the reaction of a baby worn out by trying to make sense of a busy day. Or, colic may simply be the ordinary crying of a particularly strong-willed and persistent baby.

Colic Remedies

Since no one really knows what colic is, no one really knows how to fix it. You can try laying him face-down with his stomach over a small roll of towels or a slightly warm (comfortable to the touch) hot-water bottle. Here are some other suggestions.

• Motion: Rocking, riding in a stroller or a car, swinging in a baby swing (or even a car seat swung back and forth), dancing, bicycling his legs.

• Medication: Simethicone is an over-the-counter remedy that is given to the baby in the form of drops and breaks down gas bubbles (brand names include Mylicon and Mylanta). While commonly used, evidence does not support its efficacy in treating colic. Your doctor may prescribe the drug Levsin, or hyoscyamine sulfate. This smooth muscle relaxant is believed to help relieve intestinal spasms, but it may work by generally calming the central nervous system. Use caution, as the possible side effects include drowsiness, dizziness, urinary retention, and increased sensitivity to heat because of decreased sweating.

• Dietary changes: Try eliminating dairy products from your diet if you're nursing, or, after consulting your pediatrician, switch to a soy formula if you're bottle-feeding. The connection between cow's milk and colic is anecdotal at best, but some mothers have had success with this.

And If That Doesn't Work …

In spite of reports that all of these strategies work for some babies some of the time, odds are if your baby is truly colicky none of this will help much and you'll just have to wait it out.

Colic is tough. When your baby first starts crying, you may be calm, soothingly saying, “Oh my poor sweetie, let's change your diaper and see if that helps.” By the third hour you'll feel like shouting, “WHAT? WHAT IS IT? TELL ME WHAT'S WRONG SO I CAN FIX IT!”

The point is to keep trying (and enlisting your partner, your relatives, and your friends to help.) Hold your baby, rock your baby, dance with your baby, or just sit and pat him — do anything that seems to help him calm down, even a little. It may seem pointless but you will know you're trying, and maybe your baby will know, too.

You may be surprised what works. One mother discovered it was the sound of the hairdryer that was the answer (sound, not heat). What works for one baby may not work for the next, but take the peace and quiet where you can get it.