Colic is intense, prolonged crying in an otherwise healthy baby, and the hallmark sign is crying that lasts three or more hours a day, happens at least three days a week, and continues for three weeks or longer. Up to 30 percent of healthy infants experience it, typically starting in the first six weeks of life and resolving on its own by three to four months, though some babies continue until six months.
The Crying Pattern That Points to Colic
All babies cry, so the distinction isn’t just volume or intensity. Colic follows a recognizable pattern. The crying tends to start at roughly the same time each day, most often in the late afternoon or evening. It seems to come out of nowhere, with no obvious trigger like hunger, a dirty diaper, or discomfort. And it resists the usual soothing attempts: feeding, rocking, and holding may do nothing to calm your baby down.
The episodes peak around six weeks of age. Before that, parents often assume the baby is just fussy or adjusting to life outside the womb. What separates colic from normal newborn fussiness is duration and consistency. A baby who has one rough evening isn’t colicky. A baby who screams inconsolably for three-plus hours most evenings, week after week, fits the pattern.
Physical Signs to Watch For
During a colic episode, your baby’s body will often tell you something is going on beyond ordinary crying. Common physical signs include:
- Clenched fists and stiff arms
- Pulled-up or rigid legs, sometimes drawn tight toward the belly
- Arched back, as if the baby is straining or in discomfort
- Tense, hard abdomen
- Flushed or reddened face
These signs suggest abdominal tension or gas-related discomfort. Some babies pass gas or have a bowel movement at the end of a crying spell and seem to feel better afterward, which supports the theory that gut discomfort plays a role. Between episodes, a colicky baby is otherwise normal: alert, feeding well, and gaining weight appropriately. That’s an important detail. If your baby seems unwell even when not crying, something else may be going on.
Why Colic Happens
There’s no single confirmed cause, which is one of the most frustrating things about colic. Current thinking is that it results from a combination of factors interacting at once. One leading theory focuses on the immaturity of a newborn’s digestive system. The gut is still learning to process milk, manage gas, and coordinate the muscle contractions that move food along. That immaturity can lead to cramping and discomfort.
Another well-studied theory involves gut bacteria. Colicky infants tend to have lower diversity in their gut microbiome compared to non-colicky babies. This skewed bacterial composition has been linked to excess gas production, altered motility in the intestines, and higher levels of inflammation markers in the gut. Researchers have even transplanted stool from colicky infants into mice and observed increased sensitivity to abdominal distension, which supports the idea that the bacterial environment itself contributes to discomfort.
An immature nervous system may also play a role. Some babies are simply more sensitive to stimulation, and by the end of the day, they’ve absorbed more sensory input than they can process. The crying may be a release valve. This would explain why colic episodes cluster in the evening and why dimming lights, reducing noise, and minimizing stimulation sometimes help.
How Colic Differs From Reflux
Colic and gastroesophageal reflux (GERD) share several symptoms, including crying, fussiness, and back arching, which makes them easy to confuse. The key differences lie in feeding behavior and weight gain. A baby with GERD often cries during or immediately after eating, may refuse feeds, and can have frequent forceful spit-up (six or more times a day). Some babies with GERD gag, choke, or wheeze regularly. Poor weight gain or actual weight loss is a red flag that points toward reflux rather than colic.
A colicky baby, by contrast, feeds normally and gains weight on track. The crying isn’t tied specifically to meals. Mild spit-up is common in all infants and doesn’t by itself suggest GERD. If your baby is growing well and the spit-up doesn’t seem to bother them, simple reflux is likely and not the same as GERD. But if your baby arches and screams specifically during feeds and is struggling to gain weight, that’s worth a medical evaluation.
Red Flags That Suggest Something More Serious
Colic is a diagnosis of exclusion, meaning a doctor rules out other causes first. Certain signs should prompt you to seek medical attention rather than assuming colic:
- Fever in a baby under three months
- Poor weight gain or refusal to eat
- Sudden onset of intense crying in a baby who was previously calm (this is different from the gradual pattern colic follows)
- Lethargy or unusual sleepiness between crying episodes
- Vomiting that is forceful, green, or bloody
- Unexplained bruising or swelling
- A rapidly growing head circumference
Some conditions that mimic colic require urgent attention, including inguinal hernias (a bulge in the groin area), intestinal blockages, infections, and even something as simple as a hair wrapped tightly around a finger or toe cutting off circulation. If the crying feels different from your baby’s usual pattern, or your baby seems sick rather than just upset, trust your instincts.
What Actually Helps
No single intervention reliably stops colic, but several strategies can shorten episodes or take the edge off. Physical comfort measures work best for many families: holding the baby face-down along your forearm with gentle pressure on the belly, giving a warm bath, or rubbing the baby’s abdomen in slow circles. Placing the baby on their tummy across your lap for a back rub can also help (though always put them on their back to sleep).
Environmental changes matter too. White noise from a machine, fan, or even a dryer running in the next room can be surprisingly effective. Dimming the lights and reducing stimulation during evening hours removes sensory input that may be overwhelming the baby’s nervous system. Heartbeat sounds or gentle shushing mimic the womb environment.
Feeding adjustments are worth trying. Burping more frequently during and after feeds reduces trapped air. If you’re bottle-feeding, curved bottles or those designed to collapse as they empty can minimize air intake. For formula-fed babies, your pediatrician may suggest a one-week trial of a hydrolyzed formula, where the proteins are broken into smaller pieces that are easier to digest. Some babies respond noticeably to this switch.
Probiotics have generated interest, particularly one specific strain that showed promising results in a clinical trial. Breastfed infants given this probiotic cried a median of 35 minutes per day after three weeks, compared to 90 minutes in the placebo group. However, the studies are small, and most experts don’t yet recommend probiotics as a standard colic treatment. Herbal remedies like fennel oil and sugar water have also been studied in small trials with mixed results, and the evidence isn’t strong enough to recommend them broadly.
The Hardest Part Is the Waiting
Colic resolves on its own. Most babies improve dramatically by three months, and nearly all are past it by six months. That timeline can feel unbearable when you’re in the middle of it, and parental exhaustion and distress are a real and significant part of colic. If you feel overwhelmed during an episode, it’s safe to put your baby down in their crib on their back and step out of the room for a few minutes. A crying baby in a safe space is fine. A parent at their breaking point needs a break.
Colic does not mean something is wrong with your baby, and it does not mean you’re doing something wrong. Babies who have colic develop normally and show no long-term effects from the crying. The condition is temporary, even when it doesn’t feel that way at 2 a.m.