Excessive infant crying peaks at 6 weeks and resolves by 3–4 months in most cases — but this natural history makes it a dangerous diagnosis by reassurance. The most feared diagnosis in an unsettled baby is non-accidental injury (NAI), particularly abusive head trauma — crying is the precipitant in the majority of cases. Every consultation for an unsettled baby should include a brief, non-judgemental assessment of parental distress and coping — directly asking "Sometimes babies' crying can make parents feel like they might lose control — have you felt this way?" opens a crucial conversation. Meningitis in infants may not present with neck stiffness — a bulging fontanelle, high-pitched cry, and non-specific deterioration are sufficient to warrant urgent assessment. Intussusception classically presents at 6–12 months with episodic screaming, pallor, and red-currant jelly stool — it is a surgical emergency requiring air-enema reduction.

Wessel's Rule of Three is the standard diagnostic criterion for infantile colic, but it is important to note it is a clinical description, not a pathological diagnosis. The key reassurance point is that the baby is well between episodes and feeding normally — an infant who is miserable between crying episodes does not have colic and requires further assessment. Evening clustering is the most common pattern of physiological unsettledness — it is related to circadian hormone rhythm development and cluster feeding (particularly in breastfed infants building supply), and does not represent pathology. Breastfed infants who take prolonged feeds on one breast receive more foremilk (high lactose, low fat) and less hindmilk (high fat, more satisfying) — this can cause lactose overload with abdominal distension, green frothy stools, and colic-like symptoms, managed by ensuring complete breast emptying before switching sides.

CMPA is significantly under-recognised in primary care — non-IgE-mediated CMPA in particular presents with a delayed, non-specific picture (colic-like crying, eczema, blood in stool) that is frequently labelled as "colic." The iMAP guideline (MAP — Mild-to-Moderate Allergy in Primary Care) provides a diagnostic and management pathway: in formula-fed infants with suspected non-IgE CMPA, switch to extensively hydrolysed formula (eHF) for 4 weeks; in breastfed infants, maternal dairy elimination for 4 weeks with dietitian support. If the infant improves and relapses on reintroduction, CMPA is confirmed. Gastro-oesophageal reflux is over-medicated in primary care — NICE NG1 (2015) strongly discourages prescribing PPIs and H2 blockers for uncomplicated infant reflux as evidence for benefit is lacking and harm (respiratory infection, altered gut microbiome) is established. Alginate preparations (Gaviscon Infant) have modest evidence for symptom reduction in GOR.

Hair tourniquet syndrome is a dangerous and easily missed cause of an inconsolable infant — a strand of hair (or occasionally thread) wraps around a toe, finger, or penis, causing progressive ischaemia. The infant is inconsolable, and the digit is swollen and discoloured. The hair may be invisible in the skin folds. All unsettled babies should have their digits inspected as part of the examination. Torsion of the testis can occur at any age including infancy — it presents as an inconsolable male infant with a tender, swollen, high-riding testis. The cremasteric reflex is absent. This is a 4–6 hour surgical emergency before the testis becomes non-viable. Retinal haemorrhages visible on fundoscopy are virtually pathognomonic of abusive head trauma — they occur in >80% of shaken baby cases and are rarely caused by other mechanisms. Ophthalmoscopy should be performed where NAI is suspected.

UTI is the most important investigation to exclude in any unwell infant — it is common (1–2% of febrile infants under 3 months), frequently asymptomatic except for irritability and fever, and if untreated causes renal scarring and long-term renal damage. Clean-catch urine is the preferred collection method (parent holds nappy-free baby until they urinate into a sterile pot) — bag specimens have 50–70% false-positive rate due to skin contamination. Pyloric stenosis investigation with USS is highly sensitive (>98%) — the characteristic biochemical picture of hypochloraemic hypokalaemic metabolic alkalosis (paradoxical aciduria) occurs as the infant vomits acidic gastric content, resulting in chloride and potassium depletion with renal bicarbonate conservation. This biochemistry is not present in early disease — do not wait for it to develop before referring. Non-IgE CMPA is diagnosed clinically and by response to elimination — specific IgE testing (RAST) is positive only in IgE-mediated allergy and has no role in the non-IgE subtype (which is the more common form of infant CMPA).

NICE NG143 (fever in under-5s) mandates same-day assessment for any febrile infant under 3 months — this is a hard threshold, not a guideline suggestion. The rationale is that serious bacterial infection (UTI, meningitis, septicaemia) in neonates and young infants presents with minimal clinical signs, and standard assessment tools (e.g. traffic light system) have lower specificity in this age group. Parental coping must be assessed at every consultation for an unsettled baby — asking "How are you coping?" and "Do you feel safe with the baby?" is both a safeguarding and a maternal mental health intervention. One in five mothers develops postnatal depression — PND amplifies the distress of a crying baby and reduces parental responsiveness, creating a negative cycle. Perinatal mental health referral should be considered alongside infant management. The ICON (Infant Crying is OK Normally) programme provides evidence-based parental support materials specifically designed to reduce abusive head trauma.

NICE NG1 (2015) was a landmark guideline that specifically recommended against prescribing PPIs and H2-receptor antagonists for uncomplicated infant reflux — the evidence for symptom benefit is poor, and the risks (altered gut microbiome, increased respiratory infections, community-acquired pneumonia, C. difficile susceptibility) are real. Gaviscon Infant (alginate) has modest evidence for GOR symptom reduction and is a reasonable conservative measure. Lactobacillus reuteri DSM 17938 is the specific probiotic strain with the strongest evidence for reducing colic crying duration in breastfed infants — a 2014 meta-analysis found it reduced daily crying time by ~50 minutes in breastfed infants with colic. The evidence in formula-fed infants is weaker. The iMAP guideline (developed by MAP — Milk Allergy in Primary care) provides clear, age-stratified management of CMPA — it is the consensus UK guideline for primary care CMPA management and should be the reference for formula switching decisions.

The ICON programme (Infant Crying is OK Normally) is an evidence-based public health intervention developed specifically to prevent abusive head trauma — it has been shown to reduce rates of abusive head trauma in participating regions by up to 47%. Every GP consultation for an unsettled baby should include ICON messaging. Walking away from a crying baby (placing in a safe place and stepping back for 5–10 minutes) is safe and should be explicitly endorsed — it prevents escalation of parental frustration to harmful intervention. Co-sleeping is a significant risk factor for sudden unexpected death in infancy (SUDI) — parents of unsettled babies who are exhausted are at higher risk of bringing the baby into bed. Proactive advice about safe sleep and the specific risks of co-sleeping while fatigued or under the influence of alcohol is essential. Vitamin D deficiency in infants causes rickets and is entirely preventable — the NHS recommends 400 IU/day for all breastfed infants from birth, yet uptake remains poor. Ask at every opportunity.

The safety-netting message for parents of unsettled babies must balance reassurance with clear escalation criteria — an overly reassuring message ("it's just colic") delays presentation of seriously unwell infants. Parental instinct ("something doesn't feel right") is a validated clinical sign that should always be taken seriously — parents who report a change in their baby's cry quality or behaviour should be seen promptly. The 4-week CMPA trial review is clinically important — partial improvement (crying reduced but not resolved, or new symptom) requires dietary reassessment with a dietitian. The Edinburgh Postnatal Depression Scale at the 6-week check is a quality indicator — NICE CG192 (antenatal and postnatal mental health) recommends it should be offered to all women at 6–8 weeks postnatally. A score ≥10 indicates possible depression; ≥13 indicates likely depression requiring active support. Do not discharge after the 6-week check without addressing EPDS score.