Infantile colic is the incessant, inconsolable, and unexplained crying or discontent of an infant within its first 5 months of life. It is very common, affecting from 10% to 40% of all infants.^{[1][2][3][4][5]}

Excessive infant crying is the most frequent reason for pediatric consultations and hospital emergency department visits in the first few weeks of life.^[1]

Fortunately, only about 5% of infants without a fever presenting to hospital with colic have a serious underlying condition.^[6] In fact, due to the low risk of serious conditions plus the possibility of infants picking up an infection in the hospital,^[7] it’s recommended that infants suspected of colic first be assessed in a non-hospital setting, when safely possible.^[8] If there is any possibility of an emergency, the infant should, of course, be seen as soon as possible in whatever setting is immediately available.

Infantile colic is most likely to occur within the first 6 weeks of life, and to resolve by 3–4 months of age.^{[9][10][11][12]}

Infantile colic can also affect caregivers: it is associated with caregiver exhaustion, depression, anxiety, and breastfeeding cessation, as well as with severe infant injury or death as a result of abuse.^[1]

Crying is the main sign of colic, but flushing of the face, clenched fists, drawing up of the legs, and flatulence can also occur.^[8] These signs of colic are more likely to occur in the late afternoon and evening hours of the day.^[13]

There are typically few, if any, quantifiable signs of colic, though fecal calprotectin can occasionally be higher in infants with colic.^{[14][15][16][17]}

The most recent diagnostic criteria for infantile colic are from the Rome IV committee. They are: recurrent and prolonged periods of crying or fussing (i.e., not crying, but not content) without an obvious cause, and without evidence of failure to thrive or illness, in infants younger than 5 months of age.^[4][1] Additionally, there is a set of criteria from 1954 that is still widely used. The Wessel criteria, or “rule of threes,” defines colic as attacks of irritability, fussing, or crying lasting 3 or more hours per day on 3 or more days per week for 3 or more weeks in an otherwise healthy baby aged 2 weeks to 4 months.^[18] Abdominal distension, fever, and prolonged lethargy are seldom found in simple colic and require investigation to rule out other significant disease.^[5]

Practice guidelines widely differ on recommendations for colic, but they do consistently agree on:

• clinical evaluation of the mother and baby
• parenting information, advice, support, and reassurance
• continuation of breastfeeding
• probiotic supplementation in breastfed-only infants^[1]

Pharmacological treatment of colic is seldom indicated.^[1][19]

The utility of simethicone (which aims to prevent gas bubbles from forming in the gastrointestinal tract) for colic is inconclusive or unfavorable, with moderate to low quality evidence.^[1][19][10]

Dicyclomine hydrochloride was effective for reducing crying time,^[20] but is not approved for infants less than 6 months old due to side effects and is not recommended.^[21] Cimetropium bromide might be effective,^[22] but has possible adverse effects and is not approved for use in infants in Canada and the USA.^[23][10]

Proton pump inhibitors are ineffective compared to placebo for treating colic, and may have significant adverse effects.^{[24][25][4][26]}

Probiotics, particularly Lactobacillus reuteri, have some of the strongest research for colic, with overall research quality ranging from low to high.^{[27][28][29][30][31][32][33][34][35][36]} Generally, these studies gave probiotics to the mother during pregnancy and to the infant after birth.^[27] No serious adverse events were reported.^[27][1]

Fennel may be effective. In one study, fennel reduced total crying time by 72 minutes per day on average.^[35] In another study, 65% of the participants taking 0.1% fennel seed oil resolved their colic, compared to 24% in the control group.^[37] Evidence was rated as moderate quality.^[19]

Sucrose was found in one study to reduce infant crying time by 101 minutes per day on average.^[38] However, the evidence for this has been rated as very low quality.^[19]

A trial combining fennel, chamomile, lemon balm, vitamin b1, vitamin b5, and vitamin b6 reduced crying time in infants with colic in the supplement group by 124 minutes, versus a reduction of 29 minutes in the placebo group.^[39] The evidence for this was also rated as very low quality.^[11]

No serious adverse events were reported for these supplements in colic.^[19]

Some clinical practice guidelines recommend maternal dietary modification for colic, but not all do. The American Academy of Family Physicians’ 2015 national guidelines for colic recommend elimination of common allergens from the maternal diet, whereas the UK and Irish national guidelines for infantile colic do not recommend modifying the maternal diet.^[1][40] A recent Cochrane review examined the evidence for dietary modifications for infantile colic. Due to the effects being small, and the evidence being rated as very low quality (because of small sizes of studies, and the high risks of bias), no specific interventions were recommended.^[11] However, some of the trials in this review are worth examining. Infants using a hypoallergenic (hydrolyzed) formula, compared to standard formula, had a greater reduction in crying time (on average 101 minutes per day) after 1 week. However, the number of infants who responded to the intervention was not significantly different between groups (8 of 23 infants in the hypoallergenic group versus 5 of 23 in the standard group).^[41] In addition, a partially-hypoallergenic formula (lower lactose, partially hydrolyzed), compared to standard formula with simethicone, had fewer episodes of colic after 2 weeks.^[42] Formula-fed infants with colic and atopic conditions (such as eczema or psoriasis) may have a higher likelihood of improving their colic with hypoallergenic formula, though much of the evidence is not based on randomized controlled trials, but instead clinical reasoning.^[43][10] Soy-based formulas have insufficient quality evidence for colic to warrant recommendation.^[10][44][45] Maternal diet may affect infantile colic: a group of mothers who excluded the allergens cow’s milk, eggs, peanuts, tree nuts, wheat, soy, and fish improved their breastfed babies’ colic compared to a group that did not. 74% of the low-allergen-group babies reduced their crying and fussing duration by more than 25%, compared to 37% of babies in the control group.^[46]

Chiropractic medicine and osteopathy have not shown any significant effect on colic in studies at low risk of bias.^[47][48][49]

In general, the higher-quality research on acupuncture indicates that it is not clinically more effective than placebo.^[45] Increased infant carrying throughout the day (besides during feeding and in response to crying) does not seem to reduce infant crying.^[50] Also, a car ride simulator was not effective for reducing crying.^[51] Alternatively, one study found that reduced stimulation of the infant (by not lifting and patting the baby “excessively,” and giving the infant time to fall asleep on its own despite “a certain amount of crying”) may be effective to reduce colic; however, this study suffered from serious methodological flaws, reducing confidence in its findings.^[52] Overall, evidence across each of these interventions was rated as low quality.^[10] Besides the infant, it is important to assess and treat caregiver depression, anxiety, and/or exhaustion. Otherwise, colic can lead to adversarial or alienated feelings toward the unsoothable infant; it increases the risk of shaken infant syndrome and other forms of abuse, which can be clinical emergencies.^[4] Importantly, caregivers should be educated on the self-limiting nature of colic, and taught that the vast majority of the time, colic is neither due to disease nor anything the caregivers have done, or not done, to their infants. Caregivers should be advised to try not to exhaust themselves, and if possible, to regularly leave their infants with others in their support network in order to have breaks.^[53][13]

While the cause of colic has not been established, there are several different factors that may contribute. These include gastrointestinal factors (such as gut flora, food intolerances, feeding frequency, inflammation and gastrointestinal immaturity), neurodevelopmental factors (such as increased intestinal motility), and drug-based factors (such as maternal smoking). Interactions between some of these factors are likely as well.^[10][27]