PURETHAL Grasses(HAL Allergy Holding BV)

This study investigates the safety of two up-dosing regimen. The safety of PURETHAL Grasses will be evaluated in a rush regimen (maximum dose reached in 3 injections during 2 weeks) compared to the conventional regimen (maximum dose reached in 6 injections during 5 weeks).
The primary parameter will be the proportion of patients who experience systemic reactions > grade I within 24 hours after injection or who need more than 2 additional injections during the up-dosing phase until the maintenance dose has been reached.
It is expected that up-dosing PURETHAL Grasses according to the rush regimen is as safe as using the conventional regimen.