An allergic reaction is an immune system response to exposure to a specific substance.
Allergic reactions are fairly common. Most reactions happen soon after contact with an allergen. An allergen is a trigger that causes the reaction after touching a certain part of the body.
Usually these reactions are mild and can be treated at home with simple methods. 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 exposure 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. People with asthma, hay fever, or a skin condition known as eczema are more likely to develop allergies.
Following are some of the common triggers: