Colic is intense, prolonged crying in an otherwise healthy baby, typically defined by the “rule of three”: crying that lasts more than three hours a day, happens more than three days a week, and continues for more than three weeks. It affects roughly 10% to 40% of infants worldwide, usually starting in the first few weeks of life, peaking around six weeks, and resolving on its own by three to four months in most cases. By six months, it’s almost always gone.
Colic isn’t a disease or an injury. It’s a pattern of extreme fussiness that doesn’t have an obvious explanation. Your baby isn’t hungry, wet, tired, or sick, yet the crying won’t stop. That distinction is what makes colic so frustrating for parents: there’s nothing visibly wrong, but something is clearly bothering the baby.
How Colic Looks and Sounds
All babies cry, so the difference between normal fussiness and colic comes down to intensity, duration, and physical signs. A colicky baby’s cry tends to be louder, higher-pitched, and harder to soothe than typical crying. The episodes often start in the late afternoon or evening with little warning, and nothing you do (feeding, rocking, changing) seems to help.
During a colic episode, you’ll often notice distinct body language: stiff or pulled-up legs, clenched fists, an arched back, and a visibly tense belly. The baby’s face may turn red or flushed. These episodes can last minutes or hours, and they tend to end as abruptly as they begin, sometimes after the baby passes gas or has a bowel movement.
What Causes It
There’s no single confirmed cause, which is part of why colic has been so difficult to treat. But research increasingly points to the gut as a major contributor. Babies with colic tend to have a different mix of bacteria in their digestive systems compared to non-colicky infants. Specifically, they show higher levels of gas-producing bacteria and lower levels of anti-inflammatory bacteria that help keep digestion comfortable. This imbalance can lead to excess gas and intestinal inflammation, which likely drives much of the discomfort.
Other factors that may play a role include an immature digestive system still learning to process milk, sensitivity to proteins in cow’s milk (whether from formula or passed through breast milk), and an underdeveloped nervous system that makes it harder for the baby to self-regulate after overstimulation. Some babies may simply have a lower threshold for sensory input, and the crying is their only way to discharge that overwhelm.
What doesn’t cause colic: it’s not a sign of bad parenting, it doesn’t mean your baby is in danger, and it occurs at equal rates regardless of birth order, feeding method, or sex.
When Crying Signals Something Else
Colic is a diagnosis of exclusion, meaning your pediatrician will want to rule out other causes first. Certain signs suggest the crying has a medical cause rather than colic:
- Fever, especially in a baby under eight weeks old
- Vomiting that’s forceful or contains bile (green fluid)
- Blood in the stool or jelly-like stools
- Poor feeding or weight loss
- Lethargy or unusual sleepiness between crying episodes
- Bruising or swelling anywhere on the body
- A high-pitched, inconsolable cry that sounds distinctly different from normal fussiness
These can point to conditions like an ear infection, a urinary tract infection, a hernia, acid reflux, or cow’s milk protein intolerance. A hair tourniquet, where a strand of hair wraps tightly around a toe or finger and cuts off circulation, is a commonly overlooked cause of sudden, unexplained crying that’s worth checking for.
Dietary Changes That Help
For formula-fed babies, switching to a hydrolyzed formula (where the milk proteins are broken into smaller pieces) can reduce crying by about an hour per day. In one study, 40% of colicky babies on a hydrolyzed formula no longer met the criteria for colic after just one week, compared to 28% on standard cow’s milk formula. This suggests that some cases of colic involve a sensitivity to intact cow’s milk proteins, even when it doesn’t rise to the level of a full allergy.
For breastfed babies, what the mother eats can make a measurable difference. A study published in Pediatrics found that when breastfeeding mothers eliminated common allergens from their diet, including cow’s milk, eggs, peanuts, tree nuts, wheat, soy, and fish, their infants’ crying and fussing decreased by about 21% on average. That’s a meaningful reduction, though it does require a significant dietary commitment. If you want to try this approach, eliminating cow’s milk alone is the most common starting point since it’s the most frequent trigger.
Probiotics and Gut Health
Because colicky babies tend to have fewer beneficial gut bacteria, probiotics have become one of the more promising interventions. In a clinical trial, colicky infants given a specific probiotic strain had their daily crying time drop to about 35 minutes per day by three weeks, compared to 90 minutes in the group that received a placebo. That’s a significant difference, and the results align with the broader finding that increasing levels of beneficial bacteria in the gut correlates with less crying.
Probiotics appear to work best in breastfed infants, and the evidence is stronger for certain strains than others. If you’re considering this option, your pediatrician can recommend an infant-specific product with strains supported by research.
Soothing Strategies That Work in the Moment
No single technique works for every baby, but several approaches can take the edge off a colic episode. Rhythmic motion, like rocking, swinging, or going for a car ride, mimics the movement babies experienced in the womb. White noise or shushing sounds can have a similar calming effect. Swaddling gives the baby a sense of containment that reduces the startle reflex. Holding the baby face-down along your forearm with gentle pressure on the belly (the “colic carry”) can help with gas discomfort.
Smaller, more frequent feedings and careful burping during and after feeds can also reduce the amount of air swallowed, which contributes to gas pain. If you’re bottle-feeding, anti-colic bottles designed to minimize air intake are worth trying.
The Toll on Parents
Colic is a baby problem, but its biggest impact is often on the adults. Hours of inconsolable crying, night after night, is genuinely one of the hardest experiences of early parenthood. Research bears this out: mothers of colicky infants are roughly twice as likely to develop symptoms of postpartum depression compared to mothers of non-colicky babies. When the inconsolable crying exceeds 20 minutes a day, that risk quadruples.
This isn’t a weakness. It’s a predictable response to an extremely stressful situation. If you’re feeling overwhelmed, angry, or emotionally numb during colic episodes, those reactions are common and worth talking to someone about. The most important safety rule during a colic episode is simple: if you feel yourself reaching a breaking point, put the baby down in a safe place like a crib and walk away for a few minutes. The baby will be fine. You need the break more than they need the holding in that moment.
Colic is temporary, even though it doesn’t feel that way at 2 a.m. Babies who have colic develop normally and show no long-term behavioral or health differences compared to babies who didn’t have it.