Food Allergy

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DIAGNOSIS

Requires a detailed history and physical examination and diagnostic tests

- skin prick test (SPT)
-serum-specific IgE testing to foods
-oral food challenges

* Referral to an allergist is IMPORTANT to confirm the diagnosis of a suspected food allergy. *Patients SHOULD avoid the food in question until assessment, and an epinephrine auto-injector should be prescribed, even if the diagnosis is uncertain.

HISTORY

It is IMPORTANT to inquire about all suspected foods and to discuss the manner of preparation. Time of onset of symptoms in relation to food exposure, symptom duration and severity, as well as reproducibility of symptom in the case of recurrent exposure SHOULD be determined. It is also IMPORTANT to ask about factors that can potentiate the allergic reaction such as exercise or alcohol.

PHYSICAL EXAMINATION

Purpose:
-to look for supporting evidence of atopy and other allergic diseases (e.g., atopic dermatitis, asthma, and allergic rhinitis).
-to rule out the presence of other conditions that may mimic food allergy.

*It is also useful for assessing overall nutritional status and growth in children.

DIAGNOSTIC TESTS

* Should be performed by an allergist

Skin Prick Test (SPT)

- a rapid, safe and sensitive method for diagnosing suspected IgE mediated food allergy.

*A positive SPT appears as a wheal and flare reaction when the responsible food is applied to the skin and pricked. It has a sensitivity of approximately 90%; however, its specificity is only around 50%. Therefore, a positive SPT alone is not sufficient for diagnosing food allergy; the patient must also have a supportive history.

* To minimize false positive results, over-testing with SPTs SHOULD be avoided. SPT should only be done for those foods that are relevant to the patient’s history. The negative predictive value of a SPT is greater than 95% and, therefore, a negative SPT generally confirms the absence of IgE mediated...
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