Food Allergies

Mitchell R. Lester
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Atopic Dermatitis (AD)
AD is a chronic, relapsing condition characterized by intense pruritus and rash. Onset of AD is usually very early in life with 90% of patients presenting before age 5. At least 30% of infants and toddlers with moderate to severe AD have FA that triggers (not causes) the disease. In some cases, it is the only trigger. Egg, milk, wheat, and soy account for over 90% of cases. Sometimes, the food allergen is ingested via breast milk. When a young child with AD has specific IgE to egg, milk, wheat, or soy, a trial elimination diet is frequently indicated. If elimination does not lead to improvement, the foods are re-introduced as tolerated. Without specific IgE, trial elimination diets can still be useful with the choice of food(s) eliminated based on the history and observation as to whether there is flaring after ingestion. Children with AD triggered by non-IgE mediated food allergies often develop morbilliform rashes on DBPCFC, rather than urticaria/angioedema typical of immediate type hypersensitivity.

EoE has variable and age-dependent presentations. In infants and toddlers it may present as food refusal, irritability with feeding, gastroesophageal reflux (GER), choking/gagging, or failure to thrive. Those same signs and symptoms may occur at other ages, but once patients are able to articulate their complaints they often describe dysphagia, odynophagia, or a sensation of food getting “stuck” (impaction) during swallowing. Bolus foods such as meat and bread are common offenders. However, EoE can have a much milder presentation as GER unresponsive to proton pump inhibitors and H2 antagonists. Patients are often highly atopic, at least as defined as being sensitized to numerous aeroallergens.

Characteristic endoscopic findings in EoE include eosinophilic microabscesses often mistaken for candidal esophagitis, esophageal concentric rings (“trachealization”), and longitudinal furrows. While the history and endoscopy frequently strongly suggest EoE, it is a biopsy diagnosis with =15 eosinophils/hpf on at least one biopsy. Enumeration of eosinophils is essential because eosinophils may be present in biopsies of GER without EoE. Multiple biopsies should be taken to avoid missing the diagnosis. The presence of eosinophils on biopsy does not indicate a specific food allergy.

EoE is sometimes dependent on a specific food and multiple foods have been implicated. In addition to evaluation for IgE-mediated food allergies, patch testing for delayed-type hypersensitivity to foods is sometimes useful. As with tests for food-specific IgE, patch testing lacks some sensitivity and specificity and must be interpreted in the context of the clinical history. Testing should be done to the most common food allergens and any specific foods the patient implicates. On a case-by-case basis, more extensive testing to foods should be considered. Trial elimination of foods the patient identifies as consistent triggers and to which there are positive test is indicated.

The EGIDs are conditions with eosinophilic infiltration in other organs of the alimentary tract. The signs and symptoms depend on the organ involved and the layer in which the eosinophils are found. Upper GI involvement results in nausea and vomiting, whereas lower GI involvement causes pain, cramping, bloating, and diarrhea. Mucosal infiltration is associated with diarrhea, muscularis involvement with cramping, and serosal involvement with abdominal pain. More than one layer may be affected. EGIDs are more common in adults than children.

EGIDs can present similarly to food protein induced enteropathy (see below), so biopsy is again required for formal diagnosis. Enumeration of eosinophils on biopsy is essential as eosinophils are commonly present in biopsies of normal stomach and intestine. The evaluation of food allergy in EGIDs is analogous to that of EoE, although there are no data on the utility of patch testing.

Non-IgE-mediated food allergies affecting young children (Table 4) can range from mild and benign to life threatening. Fortunately, the most severe are also the least common. Milk and soy are more the most common triggers. Presumably T-cell mediated, the specific immunologic mechanisms are not known. Onset of symptoms can be delayed several hours after ingestion.

Table 4: Non-IgE mediated food allergies

FPIES

Enteropathy

Proctocolitis

Onset

1 day-1 year

= 24 months

Newborn

Most common

Milk, soy

Milk, soy

Milk, soy

Less common

Grains, poultry, fish

Wheat, egg

Multiple FAs

>50% milk & soy

Rare

>50% milk & soy

Feeding  at onset

Formula

Formula

60% breast fed

Typical  resolution

2-3 years

2 years

1 year

Symptoms

Emesis

Prominent

Intermittent

No

Diarrhea

Severe

Moderate

No

Bloody stools

Severe

Rare

Yes

Edema

Acute, severe

Moderate

No

Shock

15%

No

No

FTT

Moderate

Moderate

No or minimal

 

FAs: Food allergies

FPIES: Food protein induced enterocolitis syndrome

FTT: failure to thrive



FPIES can present as a medical emergency with fever, vomiting, bloody diarrhea, leukocytosis with left shift, and hypovolemic shock. It is often initially confused with viral gastroenteritis or sepsis. It presents early in life and is more common in babies drinking formula than those who are exclusively breast fed. Cow’s milk and soy are the most common triggers with the majority reacting to both. Therefore, patients should be fed elemental formulas. Other foods are less commonly implicated. The diagnosis is usually made clinically. Biopsies may reveal eosinophils, lymphocytes, or neutrophils.

but is less severe and not life-threatening. As compared to FPIES, children with enteropathy tend to be a little older and usually only react to one food. Enteropathy can be confused with GER or lactose intolerance, but without removal of the offending food, children may fail to thrive.

Allergic proctocolitis is the most common and benign of the non-IgE-mediated food allergies, presenting early in life with bloody stools. Most affected infants are breast fed and sensitive to both milk and soy. In general, affected infants are otherwise healthy and happy. Allergic proctocolitis must be differentiated from anal fissures.

As with FA in general, the public perception of the frequency of gluten intolerance is greater than reality. Patients often identify gluten as the cause of subjective and vague complaints including fatigue and other constitutional complaints. However, only celiac disease (CD), non-celiac gluten sensitivity, and IgE-mediated grain allergy have been validated by DBPCFC.

CD can present with a wide variety of phenotypes and must be differentiated from non-celiac gluten sensitivity. While they can present in a similar manner and both require gluten avoidance, CD has other long-term health implications. Patients usually demonstrate anti-tissue transglutaminase IgA and have typical biopsies with crypt abscesses. Tests are negative in the absence of CD. Negative tests when the patient is gluten-free do not rule out the disease. In those instances, screening for HLA DQ2/DQ8 is useful as most patients with CD carry the genotype. However, only about 40% of HLA DQ2/DQ8 positive patients have CD.


References
Food Allergies Food Allergies 2/28/2016
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