What is the recommended approach for diagnosing and managing food allergies?

Recommended Approach for Diagnosing and Managing Food Allergies

The diagnosis of food allergies requires a systematic approach beginning with a detailed medical history, followed by appropriate diagnostic testing, and confirmation through oral food challenges when necessary, with referral to an allergist being essential for proper evaluation and management. 1

Diagnostic Algorithm

Step 1: Medical History and Physical Examination

A thorough medical history is crucial but insufficient alone for diagnosis 1:

• Key questions to ask:

  • What specific symptoms occurred?
  • Which food(s) triggered symptoms and has this happened more than once?
  • What quantity of food was ingested?
  • Was the food cooked/baked or raw?
  • How quickly did symptoms appear after exposure?
  • Can the food ever be eaten without symptoms?
  • Were other factors involved (exercise, alcohol, NSAIDs)?
  • What treatment was given and how long did symptoms last?

• Physical examination should focus on signs of allergic reactions but cannot alone confirm food allergy 1

Step 2: Initial Testing

Testing should only be performed when there's a suspicion of food allergy based on history, not as a screening tool 1, 2:

• Skin prick tests (SPTs):

  • High negative predictive value (>95%)
  • Low positive predictive value (<50%)
  • Should be performed by allergy specialists 1

• Serum-specific IgE tests:

  • Similar limitations to SPTs
  • Avoid using standard food panels; test only for suspected allergens 1
  • Total serum IgE is not suitable as a screening test 2

Step 3: Elimination Diet

• May be useful for diagnosing non-IgE-mediated food allergies like:

  • Food protein-induced enterocolitis syndrome (FPIES)
  • Allergic proctocolitis (AP)
  • Eosinophilic esophagitis (EoE) 1

• Warning: Prolonged elimination diets with multiple food restrictions can lead to malnutrition and should be supervised 1

Step 4: Oral Food Challenge

• Double-blind, placebo-controlled food challenge (DBPCFC) is the gold standard for diagnosis 1
• Single-blind or open challenges may be diagnostic in certain circumstances:
  • Negative results can rule out food allergy
  • Positive results should be interpreted cautiously 1
• Should be performed by specialists in a setting with emergency equipment available 1

Management Strategy

Immediate Management

• Epinephrine is the first-line treatment for anaphylaxis 1, 3
• All patients with confirmed food allergies should be prescribed epinephrine auto-injectors and trained in their use 1, 3

Long-term Management

1. Food avoidance:

   • Strict avoidance of confirmed allergens
   • Education on label reading and cross-reactive foods
   • Nutritional consultation for patients with multiple food allergies 1

2. Emergency action plan:

   • Written plan for managing accidental exposures
   • Should include when and how to use epinephrine 1

3. Education for patients, caregivers, and schools:

   • Recognition of symptoms
   • Proper use of medications
   • Avoidance strategies
   • School/daycare notification and planning 1

4. Regular follow-up:

   • Monitor for development of tolerance
   • Reassess need for continued avoidance
   • Evaluate for other allergic conditions 1

Common Pitfalls to Avoid

• Overdiagnosis: Relying solely on positive skin or blood tests without clinical correlation can lead to unnecessary dietary restrictions 1, 4

• Undertreatment: Failing to prescribe epinephrine for confirmed food allergies, even if previous reactions were mild 1, 3

• Inappropriate testing: Using unvalidated tests like IgG4 testing, intradermal food testing, or atopy patch testing 1

• Delayed referral: Patients with suspected food allergies should be promptly referred to allergists for proper evaluation 1

• Inadequate education: Patients and caregivers must understand avoidance strategies and emergency management 1

Food allergy diagnosis and management requires specialized expertise. Primary care providers should initiate the evaluation process but refer patients with suspected food allergies to allergists for comprehensive assessment and management planning 1.