Colic typically resolves on its own between 3 and 4 months of age. About 85% of cases have fully remitted by 3 months, and 90% of infants have outgrown it by 4 months. The condition is self-limiting, meaning it ends without any specific treatment, though it can feel like an eternity while you’re in the middle of it.
The Typical Colic Timeline
Colic follows a surprisingly predictable arc. It usually begins between the second and sixth week of life, with most parents noticing the first bouts of intense, inconsolable crying around weeks 2 or 3. Crying then escalates and hits its worst point around 6 weeks of age. After that peak, the episodes gradually become shorter and less frequent until they fade out entirely, usually somewhere between 12 and 16 weeks.
The formal definition of colic, sometimes called the “rule of threes,” describes it as crying that lasts at least 3 hours per day, happens on 3 or more days per week, and persists for at least 3 weeks, with no other obvious medical cause. Most of this crying clusters in the afternoon and evening hours. If your baby is right in the thick of it at 5 or 6 weeks, the hardest stretch is likely almost over.
Why It Happens (and Why It Stops)
No one has pinpointed a single cause of colic, but the strongest current evidence points to the gut. Babies with colic show signs of intestinal inflammation, with elevated levels of a protein called calprotectin in their stool that signals an immune response in the digestive tract. Their gut bacteria also look different from those of non-colicky babies. Specifically, colicky infants have significantly fewer beneficial Bifidobacterium (dropping from a median of about 10% of gut bacteria in healthy infants to just 0.3% in colicky ones) and higher rates of potentially irritating bacteria.
This imbalance likely contributes to gas, painful gut contractions, and the visible signs parents know well: legs pulled up to the belly, back arching, and a rigid, tense body. The reason colic resolves around 3 to 4 months may be that the infant gut microbiome matures and stabilizes during this window, reducing inflammation. The digestive system simply catches up.
Some researchers frame the broader pattern of early infant crying not as a disease but as a developmental phase. The “Period of PURPLE Crying” concept describes persistent, inconsolable crying that starts around 2 weeks and tapers off by 3 to 5 months, peaking during the second month. The name is meant to reassure parents that this crying has a beginning and, critically, an end.
What Helps While You Wait
Since colic resolves on its own, the goal of any intervention is to reduce suffering in the meantime, both for the baby and for you. The most widely recommended soothing approach involves five techniques designed to recreate the sensory environment of the womb: swaddling (a snug wrap), holding the baby on their side or stomach against your body, making a steady “shushing” sound that mimics blood flow through the placenta, gentle rhythmic swinging, and offering something to suck on. These techniques work best in combination and are most effective during the first two months, which happens to overlap with the worst of colic.
For breastfed infants, one specific probiotic strain (Lactobacillus reuteri DSM 17938) has shown real results in clinical trials. In one study, breastfed colicky babies given this probiotic daily for three weeks saw their median crying time drop to 35 minutes per day, compared to 90 minutes in the placebo group. The probiotic appeared to work by increasing beneficial bacteria and reducing gas-producing bacteria in the gut. This particular strain is available in commercial infant probiotic drops.
When Crying Signals Something Else
True colic happens in an otherwise healthy, well-fed, growing baby. The crying is intense but the baby is gaining weight normally, feeding well, and has no fever or other physical symptoms between episodes. If excessive crying comes alongside frequent vomiting, diarrhea, constipation, poor weight gain, feeding difficulties, or blood in the stool, those are signs of a different problem.
One condition that closely mimics colic is cow’s milk protein allergy. The overlap in symptoms is significant: both involve abdominal pain, gas, leg pulling, and back arching during crying. The key difference is that cow’s milk protein allergy almost always produces additional symptoms beyond crying alone, such as troublesome reflux, vomiting, diarrhea, or constipation. If your baby’s distress comes with any of these digestive symptoms, it is worth exploring whether a milk protein sensitivity is driving the problem, since that requires dietary changes rather than just time.
After Colic Resolves
For the vast majority of families, once colic ends, it’s simply over. Your baby will cry normal amounts, feed normally, and develop normally. That said, a large population-based study tracking children over five years found that kids with a history of colic had somewhat higher rates of functional gut issues later in childhood, including constipation, diarrhea, and irritable bowel syndrome. There was also a modest association with attention deficit hyperactivity disorder and allergic conditions like eczema and asthma. These are statistical trends across large groups, not certainties for any individual child, and they may reflect an underlying sensitivity in gut-brain signaling that showed up early as colic.
The practical takeaway: colic is temporary and harmless in itself, but if your child later develops persistent stomach complaints or behavioral concerns, the colic history is worth mentioning to their pediatrician. It can help piece the picture together.