When a baby cries excessively and for long stretches with no clear cause, it’s called colic. An estimated 20 to 30 percent of infants experience it during their first three months of life, making it one of the most common reasons new parents seek help from a pediatrician. Colic isn’t a disease. It’s a pattern of intense, prolonged crying that peaks around 6 weeks of age and almost always resolves on its own by 3 to 4 months.
How Colic Is Defined
Doctors use a framework known as the “rule of threes” to identify colic: crying that lasts at least 3 hours per day, happens on 3 or more days per week, and continues for at least 1 week. The crying typically starts in the first few weeks of life and has no obvious medical explanation. It tends to cluster in the afternoon and evening hours, and the baby may look like they’re in pain even when nothing is physically wrong.
A modified version of these criteria is sometimes used in clinical research, requiring parents to report that their baby has cried or fussed for 3 or more hours per day during 3 or more days in the preceding week. But in everyday practice, most pediatricians won’t ask you to track hours on a stopwatch. If your baby is crying intensely for long periods and nothing seems to help, that pattern alone is enough to start the conversation.
The Period of PURPLE Crying
Some healthcare providers describe this phase using the acronym PURPLE, which stands for: Peak of crying, Unexpected, Resists soothing, Pain-like face, Long-lasting, and Evening. The framing is intentional. It shifts the focus from “something is wrong with my baby” to “this is a normal developmental phase.” Babies in this period can cry for five hours a day or longer, and the crying may come and go for no apparent reason.
The PURPLE framework was designed partly to protect babies. When parents understand that the crying is temporary and not caused by anything they’re doing wrong, they’re better equipped to cope with the frustration and exhaustion that come with it.
When Colic Peaks and When It Ends
Crying intensity typically builds week by week, reaching its worst point around 6 weeks of age. After that, it gradually tapers off. Most babies show significant improvement by 12 weeks, and 90 percent have outgrown colic entirely by 3 to 4 months. For parents in the middle of it, those weeks can feel endless, but the condition has a clear expiration date for the vast majority of families.
What’s Happening in a Colicky Baby’s Gut
Colic doesn’t have a single known cause, but research increasingly points to the gut. A study published in the Journal of Pediatrics found that babies with colic had significantly higher levels of a gut inflammation marker called fecal calprotectin, about 95 micrograms per gram higher than babies without colic. This held true regardless of whether the baby was breastfed or formula-fed.
The gut bacteria of colicky babies also looked different. They had notably fewer Bifidobacteria, a type of beneficial bacteria common in healthy infant guts. In babies without colic, Bifidobacteria made up about 10 percent of the gut’s total bacteria. In colicky babies, that number dropped to just 0.3 percent. Colicky babies were also more likely to carry certain bacteria associated with gut imbalance. None of this means colic is an infection or that antibiotics are warranted. It suggests the immature digestive system is still sorting itself out, and some babies have a rougher time during that process.
What Helps (and What Doesn’t)
There’s no single soothing technique that works for every colicky baby, which is part of what makes the experience so draining. That said, many parents find partial relief with rhythmic motion (gentle rocking, car rides, vibrating bassinets), swaddling, white noise, or holding the baby in different positions. Some babies respond to skin-to-skin contact. Others calm temporarily with a pacifier or thumb sucking.
You may have heard that probiotics can help. The evidence is mixed. One well-designed trial published in The BMJ found that a commonly recommended probiotic strain made no difference in crying or fussing for breastfed infants. For formula-fed infants, it actually increased fussing by an average of 78 minutes per day compared to a placebo. That doesn’t mean all probiotics are harmful, but it does mean the popular claim that a specific strain reliably fixes colic is not well supported.
If your baby is formula-fed, your pediatrician may suggest trying a different formula, particularly a hydrolyzed version, since a small percentage of colicky babies turn out to have an intolerance to cow’s milk protein. For breastfeeding parents, some providers recommend a trial elimination of dairy from the mother’s diet. These are worth discussing with your baby’s doctor, but they don’t help every baby.
Signs That Something Else Is Going On
Colic is a diagnosis of exclusion, meaning it only applies when other causes have been ruled out. Certain red flags suggest the crying is not colic and needs medical evaluation:
- Sudden onset of persistent crying in a baby who was previously calm
- Fever, vomiting, or bloody stools
- Poor weight gain or feeding difficulties
- Rapid increase in head size
- Unexplained bruising or injuries
A baby who has been crying excessively since their first weeks and is otherwise growing well, feeding normally, and alert between episodes fits the typical colic pattern. A baby whose crying changes suddenly or comes with other symptoms may have something different going on.
Taking Care of Yourself Through It
Caring for a baby who cries for hours every day is one of the hardest experiences in early parenthood. Exhaustion, frustration, guilt, and even anger are all normal responses. None of those feelings mean you’re failing as a parent.
If you feel overwhelmed, it is always safe to place your baby on their back in a crib and step away for a few minutes to collect yourself. A crying baby in a safe space is not in danger. A shaken baby is. That distinction matters more than any soothing technique. If you’re experiencing thoughts of harming yourself or your child, that’s a medical emergency, and immediate help is available through your local emergency department or a crisis line.
Tag-teaming with a partner, family member, or friend can make the difference between coping and crisis. Even 30 minutes of quiet while someone else holds the baby can reset your capacity to get through the next stretch. Colic is temporary, but the weeks it lasts are genuinely hard, and asking for help is one of the most effective things you can do.