What is the recommended approach for allergen testing and treatment?

Allergen Testing: When and How to Proceed

Allergen testing is NOT routinely indicated for all patients with suspected allergic rhinitis—most patients should be treated empirically first, and testing should be reserved for those who fail empiric therapy, have diagnostic uncertainty, or when specific allergen identification would change management. 1

Initial Approach: Empiric Treatment Without Testing

• Start with empiric treatment based on clinical diagnosis alone for patients presenting with characteristic symptoms: nasal congestion, sneezing, clear rhinorrhea, nasal/eye/palate itching, postnasal drip, or throat clearing that correlates with seasonal patterns or specific exposures (animals, plants). 1

• Physical examination findings supporting allergic rhinitis include: clear rhinorrhea, bluish or pale swollen nasal mucosa, watery eye discharge, swollen conjunctivae, allergic shiners, or nasal crease. 1

• Empiric treatment consists of: environmental controls, allergen avoidance, intranasal corticosteroids, and/or second-generation antihistamines initiated without confirmatory IgE testing. 1

• An adequate trial of empiric therapy is 2 to 4 weeks of antihistamines and moderate-dose intranasal steroids before considering testing. 1

When to Perform Allergen Testing

Proceed with specific IgE testing (skin or blood) only when: 1

• Patients fail to respond to empiric treatment after an adequate trial
• The diagnosis of allergic rhinitis remains uncertain despite treatment
• Identification of the specific allergen would alter therapy decisions (e.g., targeted avoidance, immunotherapy consideration)
• Titration of therapy requires confirmation of specific triggers

Testing Modalities: Skin vs. Blood

Skin Testing (Preferred Method)

• Skin prick testing is the first-line diagnostic test due to higher sensitivity than blood testing, immediate results (15-20 minutes), lower cost, and ability to directly observe the body's reaction. 1, 2

• Intradermal testing can be used when additional sensitivity is required or when skin prick testing is negative but clinical suspicion remains high. 1, 3

• Advantages: More sensitive than blood testing, less expensive, allows direct observation of wheal-and-flare reaction. 1

• Disadvantages: Possible systemic allergic reaction (anaphylaxis risk), may be affected by antihistamines and other medications, cannot be performed in patients with severe dermatographism or extensive eczema. 1

Blood Testing (Serum Specific IgE)

• Use blood testing when skin testing is contraindicated: patients on beta-blockers, those with severe skin conditions (dermatographism, extensive eczema), patients at high risk for anaphylaxis, or when medications cannot be discontinued. 1

• Advantages: No risk of anaphylaxis, not affected by patient medications, can be used in patients with skin conditions. 1

• Disadvantages: Less sensitive than skin testing, requires reliable laboratory, potential for laboratory errors, more expensive. 1

Critical Testing Pitfalls to Avoid

• Do NOT test for IgG antibodies or total IgE—these are not beneficial for identifying allergen triggers in allergic rhinitis, which is an IgE-mediated disease. 1, 4

• Do NOT assume all positive tests are clinically relevant—up to 54% of the general population tests positive on skin prick tests without having clinical allergic rhinitis. 1, 5, 4

• Always correlate positive test results with clinical symptoms and exposure history—sensitization (positive test) does not equal clinical allergy. 1, 5, 2, 6

• The positive predictive value of allergy testing for specific allergens (cat, ragweed) is only 44-50% when not correlated with symptoms. 1

Treatment Based on Testing Results

For Positive Tests Correlating with Symptoms

• Implement targeted allergen avoidance for identified clinically relevant allergens (remove pets, use air filtration, bed covers, acaricides for dust mites). 1

• Continue or optimize pharmacotherapy: intranasal corticosteroids remain cornerstone therapy; add second-generation antihistamines for sneezing/itching. 1, 5, 4

• Consider allergen immunotherapy (subcutaneous or sublingual) for patients with inadequate response to pharmacotherapy and environmental controls after identifying specific IgE antibodies that correlate with clinical triggers. 1, 5, 4

• Select only clinically relevant allergens for immunotherapy—do not treat all positive test results; choose allergens that correlate with the patient's symptom timing, triggering exposures, and clinical history. 1

For Negative Tests with Persistent Symptoms

• Reconsider the diagnosis—symptoms may be due to non-allergic rhinitis, structural abnormalities, or other nasal pathology. 1

• Consider intradermal testing if skin prick testing was negative but clinical suspicion remains high, particularly for house dust mite allergy. 3

• Some patients have "local allergy" with allergen-specific IgE present only in nasal tissue despite negative skin/blood tests—management of this entity is still evolving. 1

Shared Decision-Making

• Discuss with patients: costs of testing, potential adverse effects (anaphylaxis risk with skin testing), benefits of confirming diagnosis, and how results will guide treatment decisions. 1

• Choice between skin or blood testing should be made jointly, considering patient preferences, contraindications, and clinical context. 1