Is there testing available for specific food allergies?

Testing for Specific Food Allergies

Yes, there are specific diagnostic tests available for food allergies, including skin prick tests (SPT) and serum-specific IgE (sIgE) tests, which help identify foods that may provoke IgE-mediated allergic reactions. 1

Recommended Diagnostic Approaches

Initial Assessment

• Food allergy should be considered in individuals presenting with symptoms that occur within minutes to hours of ingesting food, especially if symptoms have followed ingestion of a specific food on more than one occasion 1
• Parent and patient reports of food allergies must be confirmed, as studies demonstrate that 50-90% of presumed food allergies are not actual allergies 1

Validated Testing Methods

1. Skin Prick Testing (SPT)

   • Recommended to identify foods potentially provoking IgE-mediated allergic reactions 1
   • Involves introducing allergen extracts into the skin with a positive reaction defined as a wheal at least 3mm greater than the negative control 1
   • High negative predictive value (>95%) but lower positive predictive value (<50%), meaning many false positives can occur 1
   • Antihistamines should be discontinued before testing 1

2. Serum-specific IgE Testing

   • Measures free specific serum IgE to food allergens 1
   • Available to primary care physicians but should be limited to foods reasonably suspected of provoking reactions 1
   • Using laboratory-offered standard panels of common foods is discouraged 1
   • Like SPT, has high negative predictive value but lower positive predictive value 1

3. Oral Food Challenges

   • Considered the gold standard for diagnosing food allergy 1
   • Double-blind placebo-controlled food challenge (DBPCFC) is the most accurate method 1
   • Single-blind or open food challenges may be used clinically 1
   • Should be performed in a medical facility with personnel experienced in the procedure and prepared to treat anaphylaxis 1

4. Component-Resolved Diagnostics (CRD)

   • Emerging approach that measures IgE to specific food allergen components 1
   • Increasingly used for confirming allergies when tests of sensitization show intermediate results 1
   • Can reduce the need for oral food challenges in some cases 1
   • Currently available only in specialized centers 1

Non-Recommended Testing Methods

• Intradermal testing should not be used for food allergy diagnosis 1
• Total serum IgE measurement alone is not recommended 1
• Atopy patch testing is not recommended for routine evaluation of non-contact food allergy 1
• Food-specific IgG testing is considered unproven or experimental 2
• Other alternative methods that lack scientific validation include:
  • Provocation/neutralization testing
  • Applied kinesiology
  • Cytotoxic tests
  • Electrodermal testing 2

Clinical Considerations

Interpretation of Results

• A positive test result alone (SPT or sIgE) does not establish clinical food allergy - it only indicates sensitization 1
• All positive and negative test results must be correlated with the patient's clinical history 1
• Testing without suspicion of a symptom-provoking episode is not recommended and findings can be misleading 1

Common Pitfalls

• Overreliance on positive test results without clinical correlation can lead to unnecessary dietary restrictions 2
• Testing with broad food panels without clinical suspicion often leads to false positives 1
• Failure to refer patients with suspected food allergies to allergists can delay proper diagnosis and management 1
• Using unproven alternative testing methods may endanger patients through misdiagnosis 2

Special Populations

• For children under 5 years with moderate to severe atopic dermatitis, limited food allergy testing (milk, eggs, wheat, soy, peanut) may be considered if they have persistent disease despite optimized management or history of immediate allergic reactions 1

Follow-up Management

• Food avoidance is the first line of treatment for confirmed food allergies 1
• Patients with confirmed food allergies should be prescribed both antihistamines (for mild symptoms) and epinephrine autoinjectors (for severe symptoms) 1
• Referral to an allergist is recommended for comprehensive evaluation and management 1

Food allergy testing should be performed in the context of a suggestive clinical history, and the interpretation of results requires correlation with clinical symptoms to avoid both missed diagnoses and unnecessary dietary restrictions 1.