food%20allergy%20(pediatric)
FOOD ALLERGY (PEDIATRIC)
Food allergy is an adverse reaction due to a specific immune response occurring reproducibly upon exposure to certain foods. It occurs minutes to hours after food consumption.
Immunological mechanisms can be IgE mediated, non-IgE mediated or mixed IgE and non-IgE mediated.
It may be life-threatening and is the most common cause of anaphylaxis in children.
It should be differentiated from food intolerance in which adverse reactions from exposure to food arise from non-immunological mechanisms.

Diagnosis

Specific Food Allergies (FA)

  • Common food allergens are often glycoproteins
  • Although any food can evoke an IgE-mediated reaction, some are more allergenic than others
  • For infants & young children, common allergens are cow’s milk, egg, peanut, tree nuts, wheat & soybean; for adults, these are peanuts, tree nuts, fish, crustaceans & mollusks

Cow’s milk allergy (CMA)

  • Affects 2-3% of the general population
  • May be present at birth & even in infants exclusively breastfed; not all adverse reactions to cow’s milk are allergic in nature
  • 90% of those allergic to cow’s milk will react to goat’s or sheep’s milk due to high degree of cross-reactivity
  • Exclusive breastfeeding is recommended until 4-6 months of age, unless breastfeeding is contraindicated for medical reasons
  • To meet nutritional requirements of infants w/ CMA, it is recommended to prescribe a substitute formula until at least 2 years of age
    • Extensively hydrolyzed formulae are the first choice, except in patients w/ anaphylaxis & eosinophilic esophagitis
    • Soy-based formulae should not be given in infants <6 months of age
  • Factors that predict the acquisition of tolerance include declining serum IgE levels, absence of asthma or allergic rhinitis & never being formula-fed
  • In approximately 80% of affected infants, tolerance is obtained by 3-5 years of age

Egg allergy

  • Strongly associated w/ atopic dermatitis
  • MMR vaccine may be safely given to patients w/ egg allergy
  • Patients 18-49 years w/ mild-severe egg allergy should receive influenza vaccination
  • Patients w/ egg allergy who need influenza vaccine should be referred to a clinical facility experienced in anaphylaxis management
  • In approximately 67% of affected children, tolerance is obtained by 5 years of age

Peanut allergy

  • Usually life long, often severe & potentially fatal
  • Patients can generally tolerate other beans, including soy
  • Avoidance of other legumes is not needed as clinical cross-reactions are uncommon; however, tree nuts should still be avoided

Tree nut allergy

  • Eg walnut, cashew, hazelnut, pecan, almond, pistachio
  • May be severe & potentially life-threatening; allergy is usually life long
  • Common among children w/ peanut allergy (30-50%)

Classification

Classification of Food Allergies (FA) [based on underlying immunological mechanism]

IgE-mediated food allergy

  • More common in children, involving up to 6% of children <5 years old
  • Frequently affects children w/ atopic dermatitis (AD)
    • Studies found greater likelihood of FA in younger children w/ more severe AD
  • Allergic reaction occurs immediately, w/in minutes up to 1-2 hours following exposure to the causative food allergen
  • Reactions recur upon repeated exposure; small amount of food may cause severe reactions
  • Oral allergy syndrome (Pollen-food syndrome)
    • Seen in patients allergic to pollens that cross react w/ those found in fresh vegetables & fruits
    • Oropharyngeal contact w/ food allergen results in itching, tingling & angioedema of the lips, tongue, palate & throat
  • Gastrointestinal anaphylaxis
    • Arising most commonly after ingestion of the following proteins: milk, egg, peanut, soy, cereal & fish
    • Nausea, cramping abdominal pain, vomiting, diarrhea or combination of these conditions may occur after ingestion of allergen
  • Non-gastrointestinal manifestations include cutaneous, respiratory reactions & systemic anaphylaxis
  • Life-threatening reactions are associated w/ peanuts, nuts, fish & shellfish

Non-IgE mediated food allergy

  • Studies have shown that T cells may mediate the pathogenesis of some subtypes of this food allergy
  • Often presents w/ abdominal symptoms (eg vomiting, abdominal pain, hematochezia)
  • Symptoms occur several hours after ingestion of allergen
  • Food protein-induced enterocolitis syndrome
    • Symptoms develop w/in 1-4 hours of ingestion of causative allergen
    • Typically occurs in the first few years of life & may manifest as blood-streaked stools in infants who are frequently breastfed
  • Food protein-induced allergic proctocolitis
    • Is a common transient disease of infancy, usually resolving w/in the first 2 years of life
    • Occurs w/ ingestion of cow’s, soy or human breast milk in infancy
    • May manifest as mucoid, blood-streaked stools, diarrhea, vomiting & failure to thrive
  • Food protein-induced enteropathy syndrome
    • Characterized by generalized malabsorption of nutrients, resulting in chronic diarrhea, weight loss & growth failure among infants; symptoms usually disappear by 2-3 years of age
    • Most often caused by milk allergy but soy, chicken, fish & rice may also act as allergens
  • Allergic contact dermatitis
    • Cell-mediated allergic reaction to foods or food contaminants
    • Allergic reactions initiated by contact w/ chemical components in the food

Mixed IgE & non-IgE mediated food allergy

  • Suspected when symptoms occur in a more chronic nature, do not resolve quickly, or are not closely associated w/ ingestion of the food allergen
  • Allergic eosinophilic enteropathies
    • Characterized by intense eosinophilic infiltration of specific organ involved (eg esophagus, stomach, small intestine)
    • Symptoms include vomiting, anorexia, abdominal pain, hematemesis, reflux, weight loss, anemia & failure to thrive

History

  • A key part of the diagnostic work-up is an allergy focused clinical history
  • Obtain the following information:
    • Suspected food/foods that caused the adverse reaction & the symptoms produced
    • Time interval between ingestion of food & development of symptoms
    • Amount of food that caused the reaction
    • Reproducibility of the reaction in relationship to food ingestion
    • Other cofactors [eg exercise, alcohol, infection, drugs (eg NSAIDs)]
    • Length of time from previous reaction
    • Details of previous medications for the presenting symptoms, including response to these treatments
    • For children, obtain the child’s feeding history (if breastfed, consider mother’s diet), including age of weaning
  • Important to identify comorbidities, risk & predisposing factors for possible recurrence [eg history of previous anaphylactic reactions, history of atopy, asthma even if well-controlled, adolescence, family history of atopic disease or any type of food allergy (FA)]
    • Family history remains the most practical & useful tool in identifying allergy-prone infants
    • Presence of allergic diseases in one or both parents & in a sibling increases the likelihood of allergy in a child
  • More useful in the diagnosis of immediate food-induced allergies than delayed reactions
  • Although useful, history alone is not considered diagnostic of FA

Physical Examination

  • A focused physical examination (PE) can provide signs consistent w/ food-induced adverse reaction; however, no specific findings in PE are diagnostic
  • Distinguish & recognize features of anaphylaxis from less severe allergic reactions to food
  • In patients w/ acute allergic reaction to food, airways should be checked for obstruction from laryngeal edema & bronchospasm

Laboratory Tests

  • Tests are selected based on history, which should suggest the possible allergic mechanism involved
  • Laboratory testing is of limited value in the acute care setting since treatment is of utmost importance

Skin Prick Test (SPT)

  • Also referred to as puncture or epicutaneous test
  • Helps identify foods that provoke IgE-mediated allergic reactions but SPT alone cannot be considered diagnostic
  • Useful in determining the food responsible in IgE-mediated food allergy (FA) in patients w/ confirmed FA
  • Patients should stop taking antihistamines before skin testing to avoid false negative results
    • Long-acting antihistamines should be avoided for 10 days while short-acting antihistamines for 3 days before the skin test
  • Has a low positive predictive value in the initial diagnosis of FA but a high negative predictive value
  • Positive test correlates w/ presence of allergen-specific IgE bound to the surface of cutaneous mast cells
  • Positive SPT is a wheal w/ mean diameter ≥3 mm than the negative control & flare >10 mm
  • Different from intradermal testing, which is associated w/ a greater risk of systemic adverse allergic reactions & is not recommended in the diagnosis of FA

Allergen-specific Serum IgE

  • Standard method to establish allergen sensitization
  • Helps identify foods that provoke IgE-mediated allergic reactions but serum IgE alone cannot be considered diagnostic
  • Useful when SPT cannot be done
    • When patient has extensive dermatitis or has severe dermographism
    • When patient cannot withdraw antihistamine use
    • Patient’s reaction was anaphylactic & there is great risk even for skin testing
    • Unavailability of extract or reagent for skin testing
  • Levels may be used to evaluate whether sensitization to food is increasing, stable or waning over time
    • May predict the likelihood of a reaction but not its severity

Food Elimination Diets

  • May be useful in identifying foods causing some non-IgE mediated food allergies
  • Considered diagnostic & therapeutic in patients w/ adverse reactions to foods, regardless of mechanism involved
  • When combined w/ a convincing history, food elimination diets may be enough to make a diagnosis of FA in several food-induced allergic disorders
  • If instituted for longer periods, ensure that the patient is able to meet nutritional requirements to avoid deficiencies

Oral Food Challenge

  • Considered the most definitive test for food allergy
  • May be open, single-blind, or double-blind & placebo-controlled
  • Double-blind, placebo-controlled food challenge (DBPCFC) is the gold standard in diagnosing FA
    • Disadvantages include cost, potential for severe allergic reactions & is time-consuming
  • Open or single-blind food challenges may be used in clinical setting since DBPCFC can be very expensive & inconvenient
    • When results are negative, may be diagnostic in ruling out FA
    • When results are positive, may be considered diagnostic in patients supported by history & laboratory data
  • Test should be performed under medical supervision to document the dose that provokes the reaction & to administer treatment should adverse reactions, including anaphylaxis, occur

Food-induced Anaphylaxis

  • A serious allergic reaction that has rapid onset & may be life-threatening
    • Prompt assessment & treatment are critical as death can ensue rapidly
  • Clinical features include those seen in food allergy plus respiratory compromise &/or hypotension
  • Food allergy (FA) is the most common cause of anaphylaxis
  • Individuals at high risk for fatal food-induced anaphylaxis include adolescents, those w/ history of allergic reactions, peanut/tree nut allergy, asthma, & those w/o skin manifestations
  • In cases of food-dependent, exercise-induced anaphylaxis, reactions occur depending on the temporal association between food ingestion & exercise (usually w/in 2 hours)
  • Nuts, fish, shellfish, cow’s milk, soy & eggs most commonly trigger anaphylaxis, but fruits & vegetables have also been implicated
  • Please see Anaphylaxis Disease Management Chart for more details
Digital Edition
Asia's trusted medical magazine for healthcare professionals. Get your MIMS JPOG - Malaysia digital copy today!
DOWNLOAD
Editor's Recommendations
Most Read Articles
Audrey Abella, 31 Jan 2017
Nonsteroidal anti-inflammatory drug (NSAID) treatment for patent ductus arteriosus (PDA) in preterm infants did not reduce the odds of mortality or bronchopulmonary dysplasia (BPD), a recent US study found.
Jairia Dela Cruz, 13 Oct 2016
Children born to obese mothers are at increased risk of developing autism spectrum disorder (ASD) compared with children born to normal-weight mothers, according to data from a review and meta-analysis.
Yap Te-Lu, Anette Sundfor Jacobsen, 01 Oct 2013

Antenatal hydronephrosis (ANH) is a general term used to describe the dilatation of the fetal renal pelvis and/or its calyces. In pelviectasis, there is only dilatation of the renal pelvis; while in caliectasis, there is dilatation of the calyces. ANH is the most commonly diagnosed congenital urinary tract anomaly, which is detected by prenatal screening in 1–5% of all pregnancies

Yap Te-Lu, Anette Sundfor Jacobsen, 01 Dec 2012

Antenatal hydronephrosis (ANH) is a general term used to describe the dilatation of the fetal renal pelvis and/or its calyces. In pelviectasis, there is only dilatation of the renal pelvis; while in caliectasis, there is dilatation of the calyces. ANH is the most commonly diagnosed congenital urinary tract anomaly, which is detected by prenatal screening in 1–5% of all pregnancies.