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 reactions. * Although less sensitive and more costly than SPTs, serum-specific IgE tests can also be used for diagnosing food allergy, particularly if SPTs cannot be performed or are not available. Oral Food Challenge – It involves gradual feeding of the suspected food with careful, medically-supervised assessment for any symptoms.
In the event of symptoms, feeding is discontinued and the patient is treated where appropriate. * It SHOULD only be conducted in clinics or hospitals equipped with both the personnel and equipment needed to treat anaphylaxis. Other strategies that can help assist in the diagnosis of food allergy are an elimination diet and food/symptom diaries. The elimination diet can be used for both the diagnosis and treatment of food allergy and requires complete avoidance of suspected foods or groups of foods for a given period of time (usually 1-2 weeks), while monitoring for an associated decrease in symptoms. Success of this approach in the diagnosis of food allergy depends on identifying the correct food allergen and completely eliminating it from the diet. It is limited by potential bias in both patients and physicians, and variable patient compliance with the diet. Food/symptom diaries require the patient to keep a chronological record of all foods eaten and any associated adverse symptoms. These records may be helpful for identifying the food implicated in an adverse reaction; however, they are not usually diagnostic, particularly when symptoms are delayed or infrequent. Tests such as applied kinesiology, vega machine testing and serum immunoglobulin G (IgG) blood testing HAVE NO ROLE in the diagnosis of food allergy. AGAIN, if food allergy is suspected, the food should be avoided, an epinephrine auto-injector should be prescribed, and the patient should be referred for an allergy assessment. TREATMENT *THERE IS NO TREATMENT FOR FOOD ALLERGY. * A concise, written plan for the treatment of allergic reactions resulting from accidental exposure to the food should be developed, and copies made available to the appropriate persons. Patients and their caregivers must also be educated on food avoidance, the identification and treatment of allergic and anaphylactic reactions, the appropriate use of epinephrine auto-injectors, and how to obtain immediate medical assistance. * Individuals should also be instructed to read food labels carefully, watching for hidden ingredients such as “natural flavour” or “spices” that may indicate the presence of allergens, as well as “may contain” warnings. All food-allergic patients should obtain and wear medical identification indicating their food allergy. Tables 1, 2, 3 and 4. Figure 2.