Half of systemic reactions to allergen immunotherapy are delayed, majority require treatment with epinephrine

To mitigate the risk and allow for early intervention, the Joint Task Force Allergen Immunotherapy Practice Parameter recommends that patients wait in the physician's office for 30 minutes following each injection.1Delayed systemic reactions, defined as reactions occurring more than 30 minutes after an injection, encompass 14% to 50% of all systemic reactions.3-6 Severe reactions have rarely been reported with delayed onset,3 supporting the recommended 30-minute waiting period.[...]our study suggests that current rates of delayed systemic reactions may be higher than previously reported.[...]this 10-year retrospective study found that more than half of systemic reactions from allergen immunotherapy occurred after the recommended 30-minute waiting period, with most delayed reactors treated with epinephrine.Because roughly 10% occurred after 90 minutes, it is impractical to extend the wait time to ensure all systemic reactions occur within the clinic.Characteristic Overall (n = 72) 30 min (n = 38 [52.8%]) P∗ Age (y), mean ± SD 36.8 ± 18.7 34.3 ± 20.0 38.8 ± 17.8 .33 Sex: male, n (%) 29 (40.3) 17 (51.5) 11 (29.0) .05 No. of shot visits, mean ± SD 59.0 ± 104.8 70.8 ± 125.5 49.9 ± 86.1 .44 Cluster, n (%) 20 (27.8) 6 (18.2) 14 (36.8) .11 Reaction after cluster 2/20 0/6 2/14 .99 Rush, n (%) 11 (15.3) 5 (15.1) 6 (15.8) .94 Reaction after rush 1/11 1/5 0/6 .28 Allergens, n (%) Molds 26 (36.1) 13 (39.4) 13 (34.2) .65 Cat 44 (61.1) 19 (57.8) 25 (65.8) .48 Dog 40 (55.6) 17 (51.5) 22 (57.9) .59 Horse 10 (14.1) 2 (6.1) 8 (21.6) .09 Grasses 63 (87.5) 27 (81.8) 35 (92.1) .29 Weeds 53 (73.6) 24 (72.7) 28 (73.7) .93 Trees 50 (69.4) 21 (63.6) 28 (73.7) .36 Feather 8 (11.1) 3 (9.1) 4 (10.5) .99 Dust mite 43 (59.7) 16 (48.5) 26 (68.4) .09 Cockroach 6 (8.3) 5 (15.2) 1 (2.6) .09 Venom(s) 2 (2.8) 1 (3.0) 1 (2.6) .99 Treatment, n (%) ER or UC 5 (6.9) 2 (6.1) 3 (7.9) .99 Intramuscular epinephrine Any 48 (66.7) 20 (60.6) 27 (71.1) .34 1 injection 43 (59.7) 16 (48.5) 26 (68.4) .08 2+ injections 5 (6.9) 4 (12.1) 1 (2.6) .12 Bronchodilator 15 (20.8) 9 (27.3) 6 (15.8) .26 Antihistamine 59 (81.9) 29 (87.9) 29 (76.3) .21 Systemic steroid 5 (6.9) 1 (3.0) 3 (7.9) .38 Symptoms, n (%) Skin 50 (69.4) 21 (63.6) 28 (73.7) .36 Ears 7 (9.7) 1 (3.0) 6 (15.8) .11 Eyes 18 (25.0) 8 (24.2) 9 (23.7) .99 Nose 22 (30.6) 10 (30.3) 11 (29.0) .90 Throat 23 (31.9) 13 (39.4) 10 (26.3) .24 Lungs 36 (50.0) 15 (45.5) 20 (52.6) .55 CV 6 (8.3) 3 (9.1) 3 (7.9) .99 1 L. Cox, H. Nelson, R. L