Study Objective Allergies affect up to 20% of the population of developed countries and can cause substantial individual disease burden. For some allergies, immunotherapeutic regimens ("hyposensitization") have been established, e.g. for insect venom allergies and pollen allergies. This project aims at identifying the T cell activation potential in vivo from resting T cells of patients undergoing immunotherapy (IT) via a systems biology approach. For the participants, it involves blood draws and stool collection as well as gathering some basic medical information. The participation takes one week for patients undergoing insect venom IT and three months for patients undergoing pollen IT.