For new parents, the sound of their baby crying is the most unsettling experience of early parenthood. When the crying is prolonged, high-pitched, and inconsolable happening day after day despite feeding, changing, and every attempt to comfort the word that usually follows is colic. Colic is not an illness, and it is not something parents cause. It is one of the most common and most misunderstood conditions of early infancy. Understanding what causes colic in babies, what can be done to soothe it, and when crying is something more than colic, gives parents a clearer, calmer framework for one of the most testing periods of a child's first year.
What Is Colic?
Colic is defined by the "Rule of Threes": crying for more than three hours a day, at least three days per week, for more than three weeks in an otherwise healthy, well-fed baby.
It typically begins at two to three weeks of age, peaks between six and eight weeks, and in most cases resolves on its own by three to four months. The baby may clench their fists, pull their knees to their chest, arch their back, and appear to be in significant distress. Their abdomen may look bloated, and the crying is often worse in the late afternoon and evening.
Colic does not indicate illness. Babies with colic eat normally, gain weight appropriately, and are otherwise healthy. The crying, however intense, is not a signal that something is medically wrong.
What Causes Colic in Babies?
This is the question parents ask most urgently, and the honest answer is that no single confirmed cause has been identified. Researchers do not know the exact reason babies get colic. What current research does suggest is that several factors likely contribute, often in combination.
Digestive Immaturity
The digestive system of a newborn is still developing. The intestinal muscles that propel food through the gut, the enzyme systems that break down certain sugars, and the nerve signalling between gut and brain are all immature in the first weeks of life.
This immaturity means gas can accumulate more easily, intestinal contractions may be more irregular, and the baby may experience discomfort from normal digestive processes that an older infant or adult would not notice. The legs-up, tummy-tensed position that colicky babies adopt is consistent with intestinal discomfort.
Gut Microbiome Differences
Research over the past decade has identified gut microbiome composition as one of the most promising areas of investigation in understanding what causes colic in babies.
Studies consistently find that babies with colic have different gut bacterial populations compared to non-colicky babies, with lower levels of protective Lactobacillus reuteri species and higher levels of gas-producing bacteria. This altered microbiome may increase intestinal gas production and gut permeability, contributing to the pain and discomfort that drives colic crying.
This finding is also the scientific basis for the growing interest in probiotics as a colic management strategy, discussed further below.
Cow's Milk Protein Sensitivity
In a proportion of babies both formula-fed and breastfed sensitivity to cow's milk proteins is a contributing factor to excessive crying.
In formula-fed babies, cow's milk proteins in standard formula can trigger gut inflammation and discomfort
In breastfed babies, cow's milk proteins from the mother's diet transfer into breast milk and can cause the same response in a sensitive infant
Associated features such as eczema, a rash around the mouth, mucousy or bloody stools, and diarrhoea alongside excessive crying make cow's milk protein allergy more likely than simple colic A paediatrician may recommend a trial of hypoallergenic formula for formula-fed babies, or elimination of dairy from the breastfeeding mother's diet, to assess whether this is contributing.
Overfeeding and Feeding Technique Issues
Feeding-related factors are among the most modifiable contributors to what causes colic in babies. Overfeeding stretches the stomach and speeds gastric emptying, causing gas and discomfort Swallowing excess air during feeding, from a bottle with too fast a flow, poor latch during breastfeeding, or vigorous sucking, introduces air into the gut
Bottle-fed babies often swallow more air than breastfed babies unless feeding position and pacing are specifically managed
In breastfed babies, an oversupply of foremilk (low-fat, high-lactose milk at the start of a feed) before the baby reaches the fattier hindmilk can cause increased gas and gut discomfort
Adjusting feeding position, bottle teat flow rate, and ensuring the baby is properly burped after feeds can make a meaningful difference in feeding-related colic.
Sensory Sensitivity and Nervous System Immaturity
Some babies appear to have a lower threshold for sensory stimulation. Noise, light, activity, and the general stimulation of the environment outside the womb can be genuinely overwhelming for certain infants, producing a state of overstimulation that expresses itself as prolonged, inconsolable crying. The nervous system that regulates responses to external stimuli is still developing in the first months of life. Babies who have not yet developed effective self-regulation mechanisms the ability to calm themselves in response to overstimulation may cry more intensely and for longer than others in the same environment.
Gastro-Oesophageal Reflux
Gastro-oesophageal reflux (GOR), where stomach contents travel back up the oesophagus, is common in young infants because the lower oesophageal sphincter is not yet fully mature. In most babies, reflux is entirely silent and causes no distress. In some, it causes discomfort, arching of the back, and crying, particularly after feeds.
Reflux is frequently assumed to be the cause of colic, but evidence does not support treating all colicky babies for reflux. A paediatrician can assess whether the baby's symptoms suggest genuine reflux disease (GORD) rather than simple colic, and whether any intervention is warranted.
What Does Not Cause Colic
Several commonly held beliefs about what causes colic in babies are not supported by evidence.
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Colic is not caused by bad parenting or by a parent being anxious or stressed
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It is not caused by breastfeeding or by the specific foods a breastfeeding mother eats, unless cow's milk protein sensitivity is specifically identified
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It is not a sign that the baby is ill, hungry, or not bonded with their parents
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It is not caused by a specific feeding schedule or routine
Parents should hear this clearly: colic is not something you are doing wrong.
What Actually Helps Soothing Strategies With Evidence
No single technique reliably calms all colicky babies. However, several approaches have enough evidence behind them to be genuinely worth trying.
Probiotics
Lactobacillus reuteri supplementation has the strongest evidence base of any pharmacological or nutritional intervention for colic in breastfed babies. Multiple studies have shown significant reductions in daily crying time in breastfed infants who received L. reuteri probiotic drops compared to placebo. The benefit appears less consistent in formula-fed infants.
Probiotic drops for infants are widely available and safe. A paediatrician should be consulted before starting, particularly for premature infants.
Abdominal Massage
A scoping review published in 2025 examined seven randomised controlled trials of manual interventions for colic including abdominal massage, paediatric Tuina, and reflexology. Five of seven trials found significant reductions in daily crying time (ranging from 0.6 to 6.6 hours) and three found meaningful gains in infant sleep duration. Abdominal massage in particular is safe, free, and something parents can learn to do at home.
Soothing Techniques That May Help
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Holding and carrying the baby, particularly upright against the chest
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Gentle rhythmic rocking or movement
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Swaddling snugly in a blanket (until the baby begins rolling)
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White noise, including the sound of running water or a fan
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Offering a pacifier (non-nutritive sucking can be calming)
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Reducing stimulation: dim lights, quieter environment, calm interactions
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A warm bath for mild soothing relief
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Changing the baby's position during and after feeds to reduce gas
What Is Not Recommended
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Simethicone (gripe water / anti-gas drops): widely used but clinical trial evidence does not consistently support its effectiveness over placebo
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Herbal teas or supplements not specifically recommended by a paediatrician
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Eliminating multiple food groups from the breastfeeding mother's diet without paediatric guidance, which risks maternal nutritional deficiency
When Is Crying Not Colic? When to See a Paediatrician
Colic resolves on its own. But not all excessive crying in infants is colic, and it is important for parents to know the signs that indicate a different, potentially serious cause.
Consult a paediatrician promptly if:
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The baby has a fever alongside the crying
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The baby is vomiting forcefully or repeatedly
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There is blood or mucus in the stools
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The baby is losing weight or not gaining weight adequately
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The crying began suddenly after a period of relative calm (colic does not typically appear suddenly)
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The crying is accompanied by a distended or hard abdomen that does not soften
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The baby appears pale, limp, unusually lethargic, or difficult to rouse
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The crying persists beyond four months of age without any improvement
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You notice a rash, particularly around the mouth or in the nappy area, alongside crying Any of these features mean the crying has a cause that needs to be found and treated, not simply managed with soothing techniques at home.
Meet Dr. R. Ezhilarasan: Paediatrician and Neonatologist at Humayun Hospital
When colic is severe, persistent, or when parents are not sure whether their baby's crying fits the colic pattern or something more, the right specialist makes a meaningful difference.
Dr. R. Ezhilarasan is a Paediatrician and Neonatologist at Humayun Hospital, T Nagar, Chennai, holding qualifications of MBBS, MD, and DM, with over 23 years of expertise in neonatology and paediatrics.
His clinical scope covers:
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Neonatal intensive care and management of premature newborns
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Advanced respiratory support in neonates
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Nutritional management in early infancy
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Cardiac and neurological conditions in newborns
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Neonatal jaundice management
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Developmental follow-up in infants and young children
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Infection control in the neonatal and paediatric setting
Beyond clinical care, Dr. Ezhilarasan is passionate about family support, ensuring that both the infant and the family are guided through the challenges of early life with expertise and compassion. He also serves as a Visiting Teaching Professor of Neonatology, shaping the next generation of neonatal specialists.
For parents in T Nagar and across Chennai who are concerned about their baby's crying, Dr. Ezhilarasan provides a thorough clinical assessment that distinguishes straightforward colic from conditions that require treatment, and supports families through one of the most demanding phases of early parenthood.
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