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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Non-IgE-mediated gastrointestinal allergy

Paediatrics and child health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Acute FPIES or gastrointestinal compromise

Repetitive vomiting with pallor, lethargy, hypotension, hypothermia or dehydration one to four hours after a food can represent acute food protein-induced enterocolitis syndrome and mimic sepsis.

Action: Use ABCDE, obtain vascular access, check glucose and electrolytes, give rapid isotonic fluid under paediatric resuscitation guidance and involve paediatric allergy; adrenaline is reserved for coexisting IgE-mediated airway, breathing or circulation features.

Overview

Recognise delayed food-allergic gastrointestinal phenotypes, distinguish them from immediate IgE allergy and common infant disorders, and confirm diagnosis with time-limited elimination followed by planned reintroduction while protecting growth.

Define the phenotype and tempo. Ask exact feeding, breast or formula exposure, food introduction, delay to vomiting or stool change, blood, mucus, diarrhoea, reflux, eczema, pallor, lethargy and recovery. Plot weight and length. Immediate hives, swelling or wheeze redirects to IgE-mediated allergy, while bile, guarding or shock triggers an emergency differential.

Food protein-induced allergic proctocolitis usually affects a thriving young infant with small streaks of blood or mucus. Enteropathy produces more sustained diarrhoea, vomiting and growth or protein effects. Acute FPIES produces repetitive vomiting one to four hours after a trigger with pallor and lethargy; diarrhoea can follow later. Chronic FPIES causes intermittent exposure-related vomiting, diarrhoea and poor growth.

There is no single diagnostic biomarker. Specific IgE or skin-prick testing is unnecessary for a purely delayed history unless immediate symptoms, severe eczema or prolonged avoidance suggests mixed disease. Stool inflammatory tests are nonspecific in infancy. Investigate FBC, albumin, electrolytes, infection, coeliac or inflammatory disease when severity and red flags indicate.

Aetiology

01

Cow milk protein response

Cell-mediated reactions to cow's-milk proteins cause proctocolitis, enteropathy or enterocolitis, particularly during early infancy and formula exposure.

02

Other food proteins

Soya, egg, wheat, oat, rice and other foods can trigger delayed gastrointestinal allergy, with regional and individual variation.

03

Immature mucosal immunity

Developing intestinal barrier and regulatory responses in infancy permit food-specific inflammation that commonly resolves as tolerance matures.

04

Mixed allergic disease

Some children have both delayed gastrointestinal symptoms and immediate IgE sensitisation, especially with eczema or prolonged avoidance.

Pathophysiology

  1. 1
    Cell-mediated mucosal inflammation

    Food-specific T-cell and innate responses injure mucosa without rapid mast-cell IgE signalling, producing delayed and chronic symptoms.

  2. 2
    Distal colonic inflammation

    Food protein-induced allergic proctocolitis causes small-volume blood and mucus in an otherwise generally well young infant.

  3. 3
    Enteropathy and protein loss

    Small-intestinal injury impairs nutrient absorption and can cause chronic diarrhoea, vomiting, faltering growth, anaemia and clinically significant hypoalbuminaemia.

  4. 4
    FPIES fluid shift

    Acute intestinal immune activation causes profuse vomiting, diarrhoea, vasodilation and third-space loss one to four hours after ingestion.

Clinical features and red flags

Allergic proctocolitis

Small amounts of visible blood and mucus occur in a generally well thriving infant exposed to a causal food protein.

Food protein enteropathy

Chronic diarrhoea, vomiting, abdominal distension, anaemia, low albumin and faltering growth indicate more extensive mucosal injury.

Acute FPIES

Profuse repetitive vomiting with pallor, limpness or lethargy one to four hours after ingestion occurs without typical hives or wheeze.

Mixed mechanism

Delayed gastrointestinal symptoms plus immediate urticaria or positive targeted IgE suggests both cellular and mast-cell pathways.

Physiological infant symptoms

Regurgitation, colic and variable stool in a thriving infant without blood or systemic illness are common and nonspecific.

Red flags requiring action

  • Bilious vomiting, abdominal distension, guarding, haematemesis or shock requires urgent surgical and medical assessment before an allergy label.
  • Faltering growth, oedema, persistent diarrhoea, anaemia or hypoalbuminaemia indicates important enteropathy and needs early paediatric and dietetic review.
  • Repetitive delayed vomiting with pallor and lethargy after a specific food suggests FPIES even when skin tests are negative and no hives occur.

Investigations

  1. 01
    First-line feeding and symptom historyFirst stepFirst line
    Why
    Identify a reproducible delayed food relationship, phenotype, severity and nutritional effect.
    Interpretation and limitations
    Timing and response to elimination plus reintroduction are more diagnostic than a nonspecific stool or blood marker.
  2. 02
    Growth and nutritional assessment
    Why
    Detect weight, length, protein, iron, calcium and vitamin deficits before and during exclusion.
    Interpretation and limitations
    Faltering growth or hypoalbuminaemia accelerates paediatric gastroenterology, allergy and dietetic involvement.
  3. 03
    Targeted IgE testing only when mixed disease suspected
    Why
    Assess new immediate symptoms, severe eczema or possible IgE conversion after prolonged avoidance.
    Interpretation and limitations
    Negative results are expected in pure non-IgE disease and do not rule out FPIES or enteropathy.
  4. 04
    Time-limited elimination and reintroduction
    Why
    Demonstrate improvement off the suspected protein and recurrence on controlled re-exposure.
    Interpretation and limitations
    This is the practical diagnostic standard for mild delayed disease; choose home or supervised reintroduction from risk.

Differential diagnosis

01

Gastro-oesophageal reflux

Effortless regurgitation in a thriving infant without blood, diarrhoea or systemic reactions is common and usually physiological.

02

Lactose intolerance

Carbohydrate malabsorption causes gas, abdominal pain and diarrhoea but not immune inflammation, bleeding, eczema or anaphylaxis after exposure.

03

Infection

Fever, contacts, travel, acute diarrhoea and positive microbiology support infection, which can coexist with temporary secondary lactose malabsorption.

04

Coeliac or inflammatory disease

Persistent growth failure, anaemia, blood, nocturnal symptoms or systemic inflammation requires age-appropriate coeliac and IBD evaluation.

05

Surgical obstruction

Bilious vomiting, distension, focal tenderness or episodic severe pain requires urgent imaging and surgical review rather than dietary trial.

Management

01EmergencyResuscitate possible FPIESFirst stepDelayed repetitive vomiting causes lethargy, poor perfusion or dehydration.+
  1. 1Use ABCDE, monitor, obtain vascular access and check glucose, gas and electrolytes.
  2. 2Give rapid isotonic crystalloid and repeat according to perfusion under paediatric guidance.
  3. 3Exclude sepsis and surgical disease while documenting the exact food and delay.
02TrialTest a delayed allergy hypothesisMild or moderate symptoms fit non-IgE cow's-milk or food allergy.+
  1. 1Agree one complete two- to six-week elimination with dietetic replacement and objective outcomes.
  2. 2Continue breastfeeding or use an appropriate extensively hydrolysed formula when needed.
  3. 3Reintroduce the food as planned to confirm causality unless severity requires supervised challenge.

Complications

01

Hypovolaemic shock

Acute FPIES can cause profound fluid loss, poor perfusion, acidosis and apparent septic shock after trigger ingestion.

02

Growth and micronutrient failure

Ongoing enteropathy or poorly replaced exclusions impair energy, protein, iron, calcium, vitamin D and developmental nutrition.

03

Feeding aversion

Pain, vomiting and repeated restriction can create oral avoidance, texture delay and family anxiety beyond resolution of inflammation.

04

Acquisition of IgE sensitisation

A minority develop immediate reactivity during avoidance, so new rapid symptoms or prolonged exclusion changes reintroduction safety.

Monitoring and follow-up

  • Plot weight and length during elimination and after reintroduction, using shorter intervals for previous faltering growth.
  • Record stool blood, vomiting delay, frequency, feeding, eczema and systemic symptoms against exact exposures.
  • Check maternal or child calcium, vitamin D, protein and energy replacement when milk is excluded.
  • Review whether symptoms actually improved within the agreed trial and stop ineffective restriction promptly.
  • Reassess for new immediate symptoms before a milk ladder or other home reintroduction.
  • Ensure previous FPIES families have a written emergency letter, trigger list and supervised challenge plan.
  • Address oral aversion and texture delay early with dietetic and speech or feeding support.

Special situations

Reintroduction completes diagnosis

Natural fluctuation makes improvement during elimination nonspecific until planned re-exposure tests whether the food truly caused symptoms.

Lactose is not protein

Lactose-free cow's-milk formula can still trigger cow's-milk protein allergy because the immune target remains present.

FPIES looks septic

Profound pallor, lethargy and acidosis after delayed vomiting can mimic infection and deserves the same physiological resuscitation.

Negative IgE is expected

Pure non-IgE disease is cell mediated, so negative skin and blood sensitisation tests do not refute the clinical phenotype.

Restriction can become disease

Multiple poorly replaced exclusions cause growth failure and feeding aversion even after the original gut inflammation has resolved.

Common pitfalls

  1. 01

    Diagnosing delayed allergy from infant reflux alone.

  2. 02

    Using lactose-free formula for milk-protein allergy.

  3. 03

    Continuing an exclusion that produced no objective improvement.

  4. 04

    Failing to reintroduce and confirm mild disease.

  5. 05

    Using broad IgE or IgG panels for delayed symptoms.

  6. 06

    Attempting a home ladder after FPIES or immediate reaction.

  7. 07

    Ignoring growth and maternal nutrition during exclusion.

Practice

Two practice questions

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Paediatrics and child healthOriginal SBA

Delayed vomiting phenotype

An infant repeatedly develops profuse vomiting, pallor and lethargy two hours after eating oat but has no hives or wheeze. Which diagnosis best fits?

Choose one answer, then submit
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Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE CG116 Food AllergyNon-IgE history, elimination, reintroduction, formula choice and referral.
  • NHS Food Allergy OverviewImmediate and delayed food-allergy symptoms and diagnostic principles.
  • BSACI Cow Milk Allergy GuidelineUK specialist milk-allergy phenotypes, formula and tolerance care.
  • NICE QS118 Food AllergyDietetic assessment and diagnostic-quality standards under age 19.
  • BSACI FPIES Action PlanDelayed vomiting phenotype, emergency recognition and immediate FPIES actions.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

For mild or moderate suspected non-IgE cow's-milk allergy, remove the protein completely for two to six weeks while maintaining nutrition, then reintroduce it in a planned way. Symptom improvement without reintroduction is not proof because reflux, colic and stool patterns fluctuate naturally. Failure to improve should end the exclusion and reopen the diagnosis.

Breastfeeding continues whenever possible. A symptomatic exclusively breastfed infant may warrant a maternal dairy-elimination trial with dietetic replacement and planned reintroduction. A formula-fed infant generally uses extensively hydrolysed formula. Amino-acid formula is for severe enteropathy, poor growth, multiple allergy, anaphylaxis or failure of an adequate hydrolysate under specialist care.

Acute FPIES needs emergency fluids, glucose and electrolyte assessment and observation. Ondansetron is used by some specialist protocols for vomiting but does not replace resuscitation. Because standard adrenaline targets mast-cell anaphylaxis, it is not routine for isolated FPIES shock; give it immediately if airway, breathing or circulation features indicate coexisting IgE anaphylaxis.

Key points

  • Non-IgE gastrointestinal allergy causes symptoms hours to days after ingestion and is diagnosed clinically; skin-prick and specific-IgE tests are usually negative and do not confirm the mechanism.
  • Common phenotypes are allergic proctocolitis, enteropathy and FPIES; record age, trigger, delay, reproducibility, stool, growth and systemic state rather than using one umbrella label.
  • For suspected mild to moderate non-IgE cow's-milk allergy, use a two- to six-week supervised elimination followed by planned reintroduction to confirm that improvement was food-specific.
  • Continue breastfeeding; maternal cow's-milk elimination is used only when the breastfed infant is symptomatic and should include dietetic calcium and vitamin D planning.
  • For formula-fed infants, an extensively hydrolysed formula is generally first choice; amino-acid formula is reserved for severe disease, faltering growth, multiple allergy or failure of an adequate hydrolysed trial.
  • Do not use lactose-free formula for cow's-milk protein allergy because it still contains cow's-milk protein, and avoid goat or sheep milk because proteins cross-react.
  • Acute FPIES typically causes repetitive vomiting, pallor and lethargy one to four hours after food without urticaria or wheeze; treat fluids and physiology urgently.
Immediate urticaria, angioedema, wheeze or collapse indicates an IgE-mediated mechanism and changes testing and emergency planning.
  • Blood in stool with fever, severe pain, travel or systemic illness needs infection, inflammatory bowel and surgical assessment rather than empirical milk exclusion alone.
  • Multiple prolonged food exclusions, homemade nutritionally incomplete formula or poor feeding can cause avoidable malnutrition and requires urgent dietetic correction.
  • 05
    Phenotype-directed blood stool and endoscopy tests
    Why
    Exclude infection, coeliac disease, IBD, anatomical disease or severe protein-losing enteropathy when red flags persist.
    Interpretation and limitations
    Abnormalities may show severity but are not specific for food allergy; persistent disease needs specialist diagnosis.
    • 03EscalateRefer severe or atypical diseaseEscalationGrowth, protein loss, multiple triggers, FPIES or diagnostic red flags are present.+
    1. 1Involve paediatric allergy, gastroenterology and dietetics early and exclude competing disease.
    2. 2Use amino-acid formula only for defined severe disease or hydrolysate failure.
    3. 3Plan supervised challenge and emergency care for previous FPIES or possible mixed IgE disease.
    04ToleranceBroaden diet safelySymptoms have resolved and age or trajectory suggests developing tolerance.+
    1. 1Review current immediate-reaction risk and whether repeat targeted IgE testing is needed.
    2. 2Use a specialist-selected home ladder only for low-risk delayed disease.
    3. 3Stop unnecessary restrictions and monitor growth, feeding confidence and dietary variety.
    No broad allergy panel diagnoses delayed allergy, and food-specific IgG or atopy patch testing should not be used.
  • Reintroduction is part of diagnosis and later tolerance assessment; home milk ladder is for selected low-risk non-IgE disease, never previous FPIES or immediate reactions without specialist direction.
  • Plot weight and length, protect dietary variety and stop exclusions that fail to improve symptoms within the agreed trial.