It is generally recommended in consensus documents on allergen immunotherapy to avoid any kind of physical exercise in the 24 hours following the administration of the allergen extract but such recommendation is not supported by scientific evidence. We evaluated the risk of developing adverse reactions in a group of patients submitted to sublingual immunotherapy by performing a controlled exercise test. Eleven patients were included in the study, 8 treated with grass pollen and 3 with Parietaria pollen extract by Staloral300 (Stallergénes, Antony, France), with the build-up phase in 11 days suggested by the manufacturer and a top dose of 300 IR. At the first maintenance dose, in all patients were measured heart rate, blood pressure, FEV1, and tryptase in blood. Then the maintenance dose was assumed and the physical exercise performed by cycloergometer maintaining a heart rate around 100 b/min and measuring again tryptase, blood pressure and FEV1. The results showed that no patient had adverse reaction following physical exercise, neither showed significant changes in FEV1, blood pressure, or tryptase level, which was 5.57 +/- 4.54 mcg/l before and 5.81 +/- 4.34 mcg/l after exercise. This suggests that there is no reason to advise against physical exercise, and particularly sporting activity, in patients treated with sublingual immunotherapy thus avoiding to interfere with the subject's lifestyle and consequently with his quality of life.