Allergy Testing: How Allergists Diagnose Your Triggers

Diagnostic Workflow

Allergists use a structured approach combining history, exam, and targeted testing.

1. Detailed History (Most Important)

• Symptoms: type, timing, duration, severity.
• Triggers: suspected allergens, seasonality, environment, food, drugs.
• Personal/family atopy history.
• Response to prior treatments.

2. Physical Exam

• Skin: eczema, hives, angioedema.
• Eyes: allergic conjunctivitis.
• Nose: pale/boggy turbinates, discharge, crease.
• Lungs: wheezing, prolonged expiration.

3. Skin Prick Testing (SPT)

• Gold standard for IgE-mediated allergy.
• Small allergen droplet → lancet prick → read wheal/flare at 15–20 min.
• Positive: wheal ≥3 mm larger than negative control.
• Contraindications: extensive eczema, dermatographism, recent antihistamines (stop 5–7 days), anaphylaxis risk.

4. Serum Specific IgE (sIgE) Blood Test

• Alternative when SPT not feasible.
• Measures allergen-specific IgE antibodies.
• Results in kU/L; interpret with pre-test probability.
• Component-resolved diagnostics (CRD) for cross-reactivity (e.g., Ara h 2 for peanut).

5. Oral/Inhalation Challenge (Gold Standard for Confirmation)

• Supervised, graded exposure to suspected allergen.
• Used for food, drug, occupational allergy when history/testing discordant.
• Risk of anaphylaxis → only in equipped setting.

6. Patch Testing

• For allergic contact dermatitis (Type IV delayed hypersensitivity).
• Allergens applied to back ×48h; read at 48h and 72–96h.

After Diagnosis

Management plan: avoidance strategies, pharmacotherapy (antihistamines, nasal steroids, leukotriene modifiers), immunotherapy (SCIT/SLIT) for respiratory/venom allergy, emergency action plan (epinephrine autoinjector) for anaphylaxis risk.