Anaphylaxis
Epinephrine comes in an "auto-injector," usually called an "EpiPen."  Once its safety cap is taken off, the EpiPen just has to be pressed into the thigh, and the right amount of epinephrine will automatically be injected into the person's body.  Doctors can prescribe EpiPens to people who know they have allergies, so they can treat themselves for anaphylaxis.  Many ambulances also carry EpiPens to treat anaphylaxis.