There is a real possibility that physical activity endangers life, due to sports practice or a mismanaged disease, but is not always taken into account. Deaths while practicing sports and risk of a fatal outcome are low, and have been associated with cardiovascular problems. However, diseases of other biological systems, as well as an individual predisposition, can lead to a high risk situation while exercising. A brief review of respiratory diseases and allergies is presented, with advice and a warning in order that the patient may practice with the highest level of safety. It is also proposed the introduction of the life-threatening disease concept in the field of sports medicine is also proposed, with a rationalization of the concept of death in sport.