Adverse Reactions to Allergen Injection : The Siriraj Experience

Abstract

A retrospective review of the medical records of adult patients, who had skin testing and allergen immunotherapy at the ENT Allergy Clinic, from January 1987 to December 1999 was performed, to ascertain the incidence of adverse reactions to allergen injection. For skin prick testing, 5,879 patients with 82,306 skin tests were recorded with no adverse systemic reaction. For intradermal testing, 5,490 patients with approximately 109,800 tests were recorded and two patients developed mild systemic reactions which were probably related to the test. The systemic reaction rate to intradermal skin testing was therefore 36.4 per 100,000 patients or 2.2 systemic reactions per 100,000 intradermal tests. The overall reaction rate to both types of allergy skin test in 11,369 patients tested for aeroallergens was 0.018% or 17.6 systemic reactions per 100,000 patients. Concerning immunotherapy 42,810 allergen injections were recorded, the rate of excessive local reactions was 4.8% (4.08% were immediate and 0.77% were delayed types), the rate of systemic allergic reactions was 0.08%. None of the reactions was fatal.
   In a prospective study conducted from January 2000 to December 2001, 4,764 allergen injections were performed with 27 systemic reactions occurring in 23 patients (7 men and 16 women). Twenty-two events were classified as mild to moderate (0.46%) and 5 events were acute severe reactions (0.11%). No cases of hypotension and laryngeal edema were observed and none of the reactions was fatal. The possible risk factors for developing a systemic reaction during immunotherapy in this study were :- vaccines comprising grass/weed pollen or house-dust mite, an increased dose, symptomatic asthmatics, prior systemic reactions and changing to a new vial. The incidence of adverse reaction after allergen injection and the possible causative factors associated with immunotherapy in our clinic are similar to other reports from western countries. In order to minimize the number and the severity of systemic reaction, an allergen injection should be performed by physicians and personnel who are well aware of the risks and well trained to recognize and manage the systemic reactions immediately.