Indications for Inhalant Allergy Workup
When to Order Allergy Testing
Clinicians should perform or refer for specific IgE testing (skin or blood) when patients with respiratory symptoms fail empiric treatment, when the diagnosis remains uncertain, or when identifying the specific causative allergen is necessary to guide targeted therapy. 1
Primary Indications for Testing
Patients with chronic rhinitis symptoms (nasal congestion, rhinorrhea, sneezing, nasal itching) who do not respond adequately to empiric intranasal corticosteroids or antihistamines after 2-4 weeks of appropriate therapy 1, 2
Patients with asthma requiring evaluation for allergic triggers, particularly when asthma control remains suboptimal despite standard inhaled corticosteroid therapy 1
Patients with chronic cough lasting 3-8 weeks or longer, especially when accompanied by rhinitis symptoms or asthma, as postnasal drainage from allergic rhinitis is a leading cause of chronic cough 1
Patients with comorbid conditions including asthma, recurrent sinusitis, atopic dermatitis, or conjunctivitis, where identifying specific allergens enables comprehensive treatment planning including immunotherapy and environmental controls 1, 3
Diagnostic Uncertainty Scenarios
When distinguishing allergic from nonallergic rhinitis is clinically important, as physical examination findings (pale turbinates, clear rhinorrhea) can overlap and specific IgE testing definitively establishes allergic etiology 1
Perennial rhinitis cases where the history is less clear-cut than seasonal patterns, particularly to identify indoor allergens like dust mites, animal danders, and molds 1
Patients considering immunotherapy, as documentation of specific IgE sensitization correlating with clinical symptoms is required before initiating subcutaneous or sublingual immunotherapy 1, 2
Quality of Life and Treatment Planning
Patients whose symptoms significantly interfere with sleep quality, work or school performance, or overall functional status, where targeted allergen identification enables specific avoidance strategies 1, 3
When knowledge of specific allergens would alter management, such as implementing environmental controls (pet removal, dust mite covers, air filtration) or planning allergen-specific immunotherapy 1, 2
Patients with inadequate response to pharmacologic monotherapy who may benefit from combination therapy or immunotherapy based on identified allergen sensitivities 1, 3
Testing Methodology
Preferred Approach
Skin prick testing is the preferred diagnostic method, producing wheal-and-flare reactions within 15-20 minutes and demonstrating higher sensitivity than serum IgE testing in most comparative trials 2, 4
Serum-specific IgE testing (ImmunoCAP) serves as an alternative when skin testing is contraindicated (uncontrolled asthma, extensive dermatitis, inability to discontinue antihistamines, dermographism) or not feasible 2, 4
Common Inhalant Allergen Panels
Standard testing should include grass pollen, tree pollen, ragweed, dust mites (Dermatophagoides farinae and pteronyssinus), cat and dog dander, and common indoor molds 1, 2
Seasonal allergens warrant testing when symptoms demonstrate clear temporal patterns coinciding with specific pollen seasons 1
Critical Caveats
What NOT to Do
Do not order total serum IgE for diagnosing allergic rhinitis, as it lacks diagnostic specificity and does not identify causative allergens 2
Do not use IgG antibody testing to identify allergen triggers, as this is not validated for inhalant allergy diagnosis 2
Do not order IgE testing as a screening tool without clinical correlation or in asymptomatic patients, as positive tests without corresponding symptoms do not indicate clinically relevant allergy 2
Do not use IgE testing during immunotherapy to assess treatment efficacy, as IgE levels may paradoxically rise initially during treatment 2
Important Limitations
Positive serum IgE results do not always correlate with positive skin tests, with studies showing 11.7% of cases having positive skin tests but negative serum IgE, and 7.7% showing the reverse pattern 4
Total IgE levels above 200 IU/L significantly increase false-positive serum-specific IgE results, necessitating careful clinical correlation 4
Testing results must correlate with clinical history, as 17.7% of patients with negative RAST results still demonstrate positive allergen provocation tests, while 36.8% with high-level positive tests show negative provocation 5