There are your everyday allergic reactions, and then there is anaphylaxis.  This describes an extreme, often rapid, and potentially life-threatening reaction. The allergen may be as innocuous as a peanut, latex, aspirin or an insect bite.

During anaphylaxis, your blood pressure will drop and your airways will narrow, impeding your breathing. The reaction may also send you into shock.

Sometimes anaphylaxis symptoms will hit you a half-hour or so after being exposed to the allergen, but usually they occur within minutes, and include:

• Skin reactions, including hives along with itching, and flushed or pale skin (almost always present with anaphylaxis)
• A feeling of warmth
• The sensation of a lump in your throat
• Constriction of the airways and a swollen tongue or throat, which can cause wheezing and trouble breathing
• A weak and rapid pulse
• Nausea, vomiting or diarrhea
• Dizziness or fainting

Allergic reactions are your immune system's over-reactions. Your body is built to create antibodies to defend against harmful substances, but sometimes it will defend against non-harmful substances. Usually, and as you would expect, the chain reaction of defense mechanisms your immune system sets off won't put your life in danger. A severe allergic reaction can lead to anaphylaxis.

An anaphylactic reaction is a crisis situation. If you are with someone who is undergoing this, call 911, as her breathing or heart might stop at any time. While waiting for help to arrive, get the person into a comfortable position with their legs raised.

Oftentimes someone who is undergoing an anaphylactic attack has had them before. If so, they may be carrying appropriate medications, such as antihistamines or an autoinjector of epinephrine (aka adrenaline). The autoinjector is a combined syringe and concealed needle that injects a single dose of medication when pressed against the thigh. It is also used in cases of cardiac arrest.

The emergency medical service technicians may provide the sufferer with oxygen, intravenous antihistamines and cortisone, and/or a shot of adrenaline.