Patients receiving skin tests should be monitored for 30 minutes following testing, and treated promptly should they develop signs of a severe allergic reaction. Occasionally, a delayed anaphylactic response may occur that will require immediate care; therefore, patient education regarding how to recognize delayed anaphylaxis is vital. The generalized redness and swelling that may occur in the skin test area will usually resolve within a day or two. More severe reactions may require topical or antihistamine therapy.
Inhalation tests may cause delayed asthma attacks, even if the antigen administered in the test initially produced no response. Severe initial reactions may justify close professional observation for at least 12 hours after testing.
Intradermal testing may inadvertently result in the injection of the allergen into the circulation, with an increased risk of adverse reactions. Inhalation tests may provoke an asthma attack. Exposure to new or unsuspected allergens in any test carries the risk of anaphylaxis.
Lack of redness or swelling on a skin test indicates no allergic response. A wheal (an area of redness and swelling) exceeding 7 mm in diameter or larger than the histamine control, has a higher diagnostic value than smaller wheals.
Victoria E. DeMoranville, The Gale Group Inc., Gale, Detroit,