However, some people have a sudden, life-threatening allergic reaction within minutes, called anaphylaxis . Anaphylaxis can progress rapidly and result in shock and even death if medical help is not obtained quickly. Usually, the first exposure produces only a very mild reaction or no reaction at all. For some people, repeated exposures may lead to more serious reactions. Even a small amount of a trigger can lead to a serious reaction in some people.
Allergic reactions can affect small areas or the entire body.
Most reactions occur within seconds or minutes of exposure. However, some reactions can occur days or weeks after exposure. There are few things that do not cause an allergic reaction in some people. However, most people never have an allergic reaction. Those with a family history of allergies are more likely to develop them.