Gastrointestinal Manifestations of Food Allergy

Shereen M. Reda

Pediatr Health. 2009;3(3):217-229.

Natural History

Most GI food allergies occurring in infancy are outgrown by 3 years of age,^[5,9,21,30] except allergic eosinophilic gastropathies.^[13,14,22] Approximately 85% of children outgrow their food allergies to cow's milk, egg, soy and wheat by 5 years of age, while allergy to tree nuts, fish and shellfish persist to adulthood.^[4] Peanut allergy is likely to be a lifelong disorder for most, but not all patients. Approximately 20% of peanut allergic children younger than 2 years achieve tolerance by school age.^[61,62] Children who outgrow peanut allergy tend to have mild form of allergy with small or negative SPT over an interval of less than 3 years since the last reaction.^[63]

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Cite this: Gastrointestinal Manifestations of Food Allergy - Medscape - Jun 01, 2009.

Table 1. Cell-mediated gastrointestinal food allergy disorders.
Criteria	Dietary protein proctocolitis	Dietary protein enteropathy	Dietary protein enterocolitis
Onset age	First 1-2 months	First 6 months	First day to first year
Symptoms	Mild symptoms (healthy baby with blood-streaked stools ± diarrhea)	Severe symptoms (failure to thrive, nonbloody diarrhea, vomiting, malabsorption, edema ± anemia)	More severe symptoms (failure to thrive, bloody diarrhea, vomiting, distension, dehydration, sometimes mimicking sepsis)
Laboratory	Mild eosinophilia and occult blood in stools	Leukocytosis and hypoalbuminemia	Leukocytosis, hypoalbuminemia, acidosis and methemoglobinemia
Allergen	Breast milk (60%) or cow's milk/soy formula fed	Cow's milk, soy, cereals, egg and seafood	Cow's milk, soy, rice, poultry and seafood
Biopsy	Focal/diffuse colitis	Small bowel injury/villous atrophy	Intestinal villous injury and crypt abscesses
Prognosis	Resolves within 1 year	Resolves within 2-3 years	With treatment, 90% resolve wihtin 2-3 years

Box 1. Food intolerance (nonimmunologic adverse reactions).
Direct toxic effects: bacterial or viral contamination (gastroenteritis), toxins and food additives. Enzyme deficiency (lactase). Inborn error of metabolism (phenylketonuria and galactosemia). Pharmacological properties (tyramine in cheese). Anatomical defect (pyloric stenosis and Hirschsprung's disease). Cystic fibrosis. Malignancy. Overfeeding.

Box 2. Classification of food allergy in the gastrointestinal tract.
IgE-mediated Type I hypersensitivity. Rapid onset. Positive skin-prick test and/or in vitro radioallergosorbent test. Symptoms: itching of lips, angioedema, vomiting and abdominal cramps with or without symptoms in other targets (urticaria, rash, wheezing and anaphylaxis).
Non-IgE mediated Type IV hypersensitivity (cell mediated). Late onset. Negative skin-prick test and radioallergosorbent test. Symptoms are usually confined to the gut: vomiting, diarrhea, abdominal pain or colic and failure to gain weight.
Mixed IgE & non-IgE-mediated (allergic eosinophilic gastropathies) Variable onset. Peripheral eosinophil count, skin-prick test and serum results are inconclusive. Symptoms are confined to the gut and vary according to the site of eosinophilic inflammation.

Box 3. Factors suggesting food allergy as a cause of gastrointestinal disease.
History of acute reaction following ingestion of a particular food. Exclusion of anatomic, functional, metabolic or infectious disease. Improvement of symptoms with the elimination of suspected allergen. Young age (<3 years). Associated allergic diseases (atopic dermatitis or asthma). Family history of allergic disease.

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Executive Summary

Food allergy is an adverse immune response to food protein(s) and affects 6-8% of children less than 3 years of age. Common allergenic foods are cow's milk, soy protein, eggs, wheat, rice, peanut, tree nuts and seafood.

IgE-mediated gastrointestinal disorders

Gastrointestinal anaphylaxis: characterized by acute onset of nausea colicky abdominal pains and diarrhea following food ingestion.
Oral allergy syndrome: symptoms are localized to oropharynx (angioedema). The offenders are pollen proteins that cross-react with some food proteins. Positive skin-prick test with fresh food extract of the allergenic food is diagnostic.

Mixed IgE- & cell-mediated gastrointestinal disorders

Eosinophilic esophagitis (EE): symptoms mimicking gastroesophageal reflux but resistant to antireflux medications. EE should be suspected in any child presenting with unexplained food impaction and it is appropriate to obtain biopsy specimen of the esophagus during removal of the impacted food. Diagnosis necessitates esophageal pH monitoring and biopsy. Topical corticosteroids can be helpful in treatment of some cases.
Eosinophilic gastroenteritis: symptoms include vomiting, diarrhea, abdominal pain, poor weight gain and intestinal obstruction. The diagnosis is confirmed on biopsy findings of eosinophilic infiltration of the gut.

Non-IgE mediated gastrointestinal disorders

Usually affects infants. Symptoms are isolated to the gut mimicking gastroenteritis. The main causal food is cow's milk. Blood tests, stool analysis and atopy patch test may help diagnosis, but confirmed diagnosis is obtained by biopsy, elimination diet and food challenges.
Food protein-induced proctocolitis: characterized by blood streaks in stools in a healthy baby.
Food protein-induced enterocolitis syndrome: symptoms of severe vomiting, diarrhea, dehydration and acidosis, and mimicking sepsis.
Food protein-induced enteropathy: symptoms of vomiting, diarrhea, edema due to protein loss and steatorrhea.

Diagnosis

The main pillars of diagnosis are detailed medical history in order to identify the allergenic food, nature and severity of reaction. The diagnosis is achieved by elimination of the suspected food from the diet and oral food challenge tests. Laboratory and skin tests should be employed according to the disease phenotype such as:
- Skin-prick test is useful in the detection of an IgE-mediated reaction. Interpretation of results should be coupled with clinical history suggestive of allergy to the tested protein.
- Atopy patch test is a recent test for cell-mediated food allergies, but it is still under clinical trials and requires standardization in terms of the reagents used in the test, application methods and guidelines for interpretation.
- In vitro measurement of food-specific IgE antibodies in the serum may be useful in conditions when skin testing cannot be performed.
- Gastrointestinal tests, including endoscopic studies, biopsies and esophageal pH monitoring are used in the diagnostic work-up and follow-up of food protein-induced proctocolitis and EE.
- Elimination diet confirms the diagnosis of food allergy. In young infants, extensive hydrolyzed or amino acid-based formulas are used until clinical improvement is achieved.
- Oral food challenge tests are essential to confirm or rule out the diagnosis of allergy to the tested food, and to determine tolerance.

Treatment

Complete avoidance of the causal food should be stressed.
Restriction diet in children and extensive hydrolyzed or amino acid-based formula is indicated in young infants.
Swallowed fluticasone may be effective in EE.

Prevention

Exclusive breast feeding until the age of 4-6 months.
There is no convincing evidence that maternal manipulation of diet during pregnancy or lactation, use of soy products, or infant dietary restrictions of solid food would prevent allergy.

Natural history

Most gastrointestinal food allergies occurring in infancy are outgrown by 3-5 years of age, except allergic eosinophilic gastropathies.

Conclusion

Gastrointestinal food allergies are common in the pediatric age group and have a wide spectrum of clinical disorders with variable outcome.
Early diagnosis is required to prevent recurrence of severe symptoms and decrease morbidity.
Skin testing and food-specific IgE antibodies are useful but sometimes are inconclusive in the diagnosis of food allergy.
The definite diagnosis requires endoscopic investigations, clear response to an elimination diet and oral food challenges.

Future perspective

Noninvasive, safe and more accurate tests are to be employed in the diagnostic setting of food allergy.
Identifying responsible gene(s) of food allergy will facilitate the detection of children at risk and will enable further therapeutic interventions.
Predictors of severity of reactions and persistence of allergy will provide better management.

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