The most violent allergic reactions are the so-called anaphylactic shock: difficulty breathing, low blood pressure... and the patient may lose consciousness. Treatment opposes these symptoms, but the cause of shock is not treated because it is not known. According to one last study, nitric oxide is the main responsible (multiplied enormously) and is closely linked to a protein called eNOS. This research is being done with mice, but one day there may be effective treatment for humans with medicines to block the responsible protein.