Colic is intense, prolonged crying in an otherwise healthy baby, and the classic pattern follows what pediatricians call the “Rule of Three”: crying for more than three hours a day, more than three days a week, for more than three weeks. If your newborn fits that pattern and is feeding well, gaining weight, and healthy between episodes, colic is the most likely explanation. It affects 10 to 30 percent of infants worldwide.
When Colic Typically Starts and Stops
Most parents first notice colic between the third and sixth week after birth, though some babies show signs as early as the second week. The crying tends to peak around 6 weeks of age, which is often the hardest stretch for families. By 12 weeks, symptoms usually fade significantly, and most babies are completely past it by 3 to 4 months. This predictable arc is one of the hallmarks of colic: it arrives on a rough schedule, gets worse, then resolves on its own.
What Colic Crying Looks and Sounds Like
Colic crying is different from ordinary fussiness. The episodes tend to be louder, higher-pitched, and more urgent sounding, almost as if the baby is in pain. They often start suddenly, without an obvious trigger, and resist your usual soothing methods. Feeding, rocking, diaper changes, and holding may do nothing to stop it.
During an episode, you may notice your baby’s face turning red or flushed, their fists clenching tight, their legs pulling up toward their belly, or their back arching. These physical signs suggest abdominal discomfort, though your baby is not in any danger. Many colicky babies also pass gas or seem bloated during crying spells, which may bring brief relief before the crying starts again.
The timing tends to follow a pattern too. Colic episodes cluster in the late afternoon and evening for most babies, often starting around the same time each day. Between episodes, a colicky baby acts completely normal: feeding well, sleeping in their usual pattern, and gaining weight on track.
Why Some Babies Get Colic
There is no single established cause, which is part of what makes colic frustrating for parents. Several theories exist, and multiple factors likely contribute.
One of the strongest lines of evidence points to the gut. Research published in the Journal of Pediatrics found that colicky babies had significantly different gut bacteria compared to calm babies. Specifically, colicky infants had much lower levels of Bifidobacterium, a beneficial type of bacteria that helps keep the gut lining calm. In healthy infants, Bifidobacterium made up about 10 percent of gut bacteria; in colicky babies, it dropped to just 0.3 percent. Colicky babies also harbored higher levels of bacteria associated with inflammation. The theory is that in the first weeks of life, a baby’s gut is still being colonized by microbes, and an imbalance toward inflammatory bacteria may cause the kind of gut discomfort that drives prolonged crying.
Other proposed causes include an immature nervous system that has trouble processing stimulation, cow’s milk protein sensitivity (in formula-fed babies or through breastmilk), and gastroesophageal reflux. None of these fully explain colic on their own, and many colicky babies have no identifiable underlying issue at all.
How to Tell It’s Colic and Not Something Else
The key distinction is that a colicky baby is otherwise healthy. Between crying spells, they eat normally, produce the expected number of wet and dirty diapers, and gain weight. If any of those basics are off, something other than colic may be going on.
Watch for these red flags that suggest a different problem:
- Fever. Any fever in a baby younger than 3 months needs immediate medical attention.
- Vomiting after feedings. Occasional spit-up is normal, but forceful or repeated vomiting is not part of colic.
- Signs of dehydration. Fewer wet diapers than usual, crying without tears, or a dry mouth all warrant a call to your pediatrician.
- Poor weight gain. If your baby isn’t gaining weight steadily, the crying may signal a feeding problem or food intolerance.
- Blood in the stool. This can indicate a milk protein allergy or other gastrointestinal issue.
- Floppiness or extreme lethargy. A baby who seems unusually limp or difficult to wake between episodes needs prompt evaluation.
- Pain that keeps getting worse. Colic episodes come and go. Fussiness that escalates continuously or never lets up is a different pattern.
Getting a Diagnosis
There is no blood test or scan for colic. Your pediatrician diagnoses it by ruling other things out. They’ll check your baby’s growth, do a physical exam, and ask about the crying pattern: when it happens, how long it lasts, what you’ve tried, and whether the baby seems well between episodes. If everything checks out and the pattern matches the Rule of Three, the diagnosis is colic.
In some cases, your doctor may suggest a short trial of switching formula or, if you’re breastfeeding, eliminating dairy from your diet for a couple of weeks. This helps rule out a cow’s milk protein sensitivity, which can look identical to colic. If the crying improves, the sensitivity was likely a factor. If nothing changes, standard colic is the more likely explanation.
What Actually Helps
No single remedy works for every colicky baby, but several strategies consistently help parents manage episodes. Rhythmic motion, like gentle bouncing, swaying, or going for a car ride, often provides some relief. White noise or shushing sounds mimic the constant noise of the womb and can calm some babies mid-episode. Swaddling gives a sense of security, and holding your baby on their side or stomach across your forearm (the “colic carry”) puts gentle pressure on the belly.
Some parents find relief with infant probiotic drops containing Lactobacillus reuteri, which aligns with the gut bacteria research. The evidence is more promising for breastfed babies than formula-fed ones, and results vary. Talk with your pediatrician before starting any supplement.
What matters just as much is protecting yourself during this phase. Colic is one of the leading triggers for caregiver frustration and exhaustion. If you feel overwhelmed during a crying spell, it is always safe to place your baby on their back in the crib and step away for a few minutes. Trading off with a partner, family member, or friend gives you the breaks you need to get through the weeks until the crying resolves. The predictable timeline is the most reassuring thing about colic: it ends, and it does not cause lasting harm to your baby.