The principal investigation is the history, where a story of exposure to allergen followed by an allergic rhinitis is diagnostic, and suggests how to treat or prevent further episodes. Variation in symptoms with respect to the period of the day (e.g. allergy to dust mite is generally worse at night and early in the morning), the season (e.g. pollen allergy), location (e.g. workplace), or other factors such as administration of drugs, may give important clues to the allergen (1).
Skin prick testing assesses IgE bound to cutaneous mast cells. Its popularity arises from its low cost, simplicity, small side effect profile, and clearly discernible negative and positive response. It is also easily repeatable.
Allergen-specific IgE antibody testing also known as Radioallergosorbent testing (RAST) is useful in detecting common allergens like dust mites, pollen, pet dander. It is highly specific but not as sensitive as the skin prick test. It is preferred in situations where:
- percutaneous skin prick testing is not practical or
- a patient using medication which interferes with skin testing e.g. - antihistamines (2)
Atopy itself is suggested by a high serum IgE.
less commonly used investigation methods include ¢ nasal provocation testing
- nasal cytology (e.g., blown secretions, scraping, lavage, biopsy)
- intradermal skin testing (2)
- 1. Clinical knowledge summaries, safe practical clinical answers. Allergic rhinitis
- 2. Quillen David, Feller David B. Diagnosing Rhinitis: Allergic vs. Nonallergic. AAFP 2006; 73(9).
Last reviewed 05/2021