The hypersensitivity reaction type I describes the fast response within minutes to hours. The involved mediators are IgE. The release of various vasoactive biomolecules provokes local symptoms like rhinitis, vomiting, diarrhea and urticaria or, in an increased form, systemic symptoms like bronchoconstriction and anaphylaxis which can be fatal without treatment. A testing by means of a skin test for specific IgE can be undertaken. Examples for a type I reaction are allergic asthma or hay fever. In the dental practice a latex-allergy should be always considered.