Anaphylaxis is a severe, sometimes life-threatening, allergic reaction that occurs within minutes of exposure an allergy-causing substance (allergen). Anaphylaxis also is called anaphylactic shock.

In a severe allergic reaction, the body's immune system responds to the presence of an allergen by releasing histamine and other body chemicals. These chemicals cause the symptoms of allergies, which are usually mild but annoying, such as the runny nose of hay fever (allergic rhinitis) or the itchy rash of poison ivy. However, in some cases, the symptoms can be much worse and involve the entire body. Anaphylaxis is the most severe allergic reaction. In anaphylaxis, these immune chemicals cause serious skin symptoms, such as hives and swelling, as well as severe breathing problems, such as swelling in the throat, narrowing of the lower airways and wheezing). The chemicals also cause blood vessels to widen dramatically, which leads to a rapid, severe drop in blood pressure (shock). Anaphylaxis is a life-threatening medical emergency.

Although the specific allergen that triggers anaphylaxis may be different for each patient, it often can be traced to one of the following sources:

• Foods � Especially eggs, seafood, nuts, grains, milk and peanuts
• Drugs � Especially an antibiotic from the penicillin or cephalosporin group
• Insect stings � From bees, yellow jackets, paper wasps, hornets or fire ants
• Injected anesthetics � Procaine, lidocaine
• Dyes � Used in diagnostic X-rays and scans
• Industrial chemicals � Latex and rubber products used by health care workers
• Allergy shots (immunotherapy)

Symptoms of anaphylaxis usually occur within seconds to minutes of exposure to the allergen and range from mild to very severe. These symptoms include:

• Rapid pulse, sweating, dizziness, fainting, unconsciousness
• Wheezing, chest tightness, difficulty breathing, coughing
• Itchy hives, which may blend together to form larger areas of skin swelling
• Swelling of the lips, tongue or eyes
• Nausea, vomiting, abdominal cramps, diarrhea
• Paleness, bluish skin color
• Throat swelling, with a feeling of throat tightness, a lump in the throat, hoarseness or obstructed air flow

The doctor will ask about the patient's allergy history and about his or her exposure to any of the common allergens that trigger anaphylaxis. It is very important for the doctor to know if the patient's symptoms started soon after exposure to an allergen, for instance after eating nuts, after a bee sting or after taking an antibiotic. Because the patient may be too sick to provide this information, a family member, friend, co-worker or school nurse will need to help. People with a history of severe allergic reactions should consider wearing a medical alert identification necklace or bracelet to save valuable time in identifying the problem.

The doctor usually can diagnose anaphylaxis based on the patient's history and the results of a physical examination.

With early and appropriate treatment, cases of anaphylaxis can improve quickly within a few hours. If a person has already developed the more serious symptoms and dangerous conditions, it may take a few days to fully recover after treatment. If untreated, anaphylaxis can cause death within minutes to hours.

You can prevent anaphylaxis by avoiding the allergens that trigger your symptoms. For example, people with food allergies should always check the list of ingredients on food labels, and they should always ask the waiter about food ingredients before eating at a restaurant. If you are allergic to bee stings, you should limit gardening and lawn mowing, and you should not wear perfumes, hair sprays or bright clothing that attracts insects.

People with a history of anaphylaxis should wear a medical identification bracelet or necklace to alert others in the event of another reaction. In addition, ask your doctor if you should carry a pre-loaded syringe of epinephrine (adrenaline), a medicine used to treat anaphylaxis. At the first sign of symptoms, you or a helper (family member, co-worker, school nurse) would inject the pre-loaded epinephrine to treat your allergic reaction until you reach medical attention.

Allergy shots, also called immunotherapy, are used to gradually change the type of reaction that a person has after an insect sting. Allergy shots cause the immune system to react by producing varieties of antibodies and cells that do not cause dangerous symptoms, instead of producing antibodies and chemicals that result in allergy symptoms. On rare occasions, allergy shots also can be used to prevent certain medication allergies. Allergy shots are not used to treat food allergies, because the shots themselves are too likely to cause anaphylaxis. However, oral (swallowed) immunotherapy using extraordinarily diluted samples of allergy triggers is currently being tested as a possible new treatment for food allergy.

Some early cases of anaphylaxis can be treated with antihistamines and corticosteroids. More severe cases are life-threatening emergencies and require immediate medical attention. If available, epinephrine should be given at the first sign of a serious reaction to slow the progression of symptoms. Doctors treat anaphylaxis with the medication epinephrine and with intravenous fluids. The person also may need treatment with oxygen, mechanical ventilation (a machine helps the patient breathe temporarily), and antihistamines or corticosteroids given intravenously (into a vein).

Call for emergency assistance immediately whenever anyone has symptoms of anaphylaxis. If you have a history of severe allergic reaction and have not mentioned this to your doctor, schedule an appointment soon. He or she can review your history and help you take the necessary precautions to avoid future problems.

With prompt, appropriate treatment, most patients who have had a severe allergic reaction can recover completely. Unfortunately, even with treatment, some people die of anaphylaxis.

A person who has had anaphylaxis is at risk of future severe reactions if he or she is exposed again to the same allergen.

American Academy of Allergy, Asthma & Immunology (AAAAI)
555 East Wells St.
Suite 1100
Milwaukee, WI 53202-3823
Phone: 414-272-6071
Toll-Free: 1-800-822-2762
E-Mail: info@aaaai.org
http://www.aaaai.org/

The Food Allergy & Anaphylaxis Network
11781 Lee Jackson Highway
Suite 160
Fairfax, VA 22033-3309
Toll-Free: 1-800-929-4040
Fax: 703-691-2713
E-Mail: faan@foodallergy.org
http://www.foodallergy.org/