Background:

Immunotherapy with specific allergens is the only immune system-modifying treatment for allergic disease.

Objective:

To identify the prevalence of adverse reactions during the subcutaneous immunotherapy initiation phase in real-life conditions and possible associated risk factors.

Methods:

One-year retrospective, observational study. Epidemiological characteristics of 481 patients, type of immunotherapy used and adverse reactions were recorded.

Results:

16.8% of patients suffered atopic dermatitis, 8.9% food allergy, 4% drug allergy and 7.3 % had experienced idiopathic urticaria. Grass pollen was the main allergen. In polysensitized patients, the use of polymerized extracts that contained grasses in their composition was higher (89.2%) than that of native extracts (78.9%). A total of 1292 doses of specific immunotherapy were administered: 881 polymerized extracts and 411 depot extracts; 30 patients had an adverse reaction (6.2 %): 4.4% of those who received polymerized extract and 14.3 % of those who received a native one (OR = 3.657). In patients who received polymerized extracts, the adverse reaction was local in 82.4%, mild systemic in 11.8% and only in one it was serious systemic; 66.7 % of those who received native extract had local reactions, 25 % mild systemic and only one, serious systemic.

Conclusion:

Subcutaneous immunotherapy under real life conditions is not free of risk, but the incidence of severe reactions is very low, especially with polymerized extracts, even when grouped or ultra-rapid testing is used.