Anaphylaxis

Anaphylaxis

Definition  :

Anaphylaxis is a severe, potentially life-threatening allergic reaction. It can occur within seconds or minutes of exposure to something you're allergic to, such as the venom from a bee sting or a peanut.

The flood of chemicals released by your immune system during anaphylaxis can cause you to go into shock; your blood pressure drops suddenly and your airways narrow, blocking normal breathing. Signs and symptoms of anaphylaxis include a rapid, weak pulse, a skin rash, and nausea and vomiting. Common triggers of anaphylaxis include certain foods, some medications, insect venom and latex.

Anaphylaxis requires an immediate trip to the emergency department and an injection of epinephrine. If anaphylaxis isn't treated right away, it can lead to unconsciousness or even death.

Symptoms:

Anaphylaxis symptoms usually occur within minutes of exposure to an allergen. Sometimes, however, anaphylaxis can occur a half-hour or longer after exposure. Anaphylaxis symptoms include:

• Skin reactions, including hives along with itching, 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 feeling of impending doom
• A weak and rapid pulse
• Nausea, vomiting or diarrhea
• Dizziness or fainting

When to see a doctor
If you, your child or someone else you're with has a severe allergic reaction, call 911 or seek emergency medical help. If the person having the attack carries an epinephrine autoinjector (such as an EpiPen, EpiPen Jr or Twinject), give him or her a shot right away. Even if symptoms improve after an emergency epinephrine injection, a visit to the emergency department is still necessary to make sure symptoms don't return.

If you or your child have had a severe allergy attack or any signs and symptoms of anaphylaxis in the past, make an appointment to see your doctor. The diagnosis and long-term management of anaphylaxis are complicated, so you'll probably need to see a doctor who specializes in allergies and immunology.

Causes:


Your immune system produces antibodies that defend against foreign substances. This is good when a foreign substance is harmful (such as certain bacteria or viruses). But some people's immune systems overreact to substances that shouldn't cause an allergic reaction. When this occurs, the immune 
system sets off a chemical chain reaction, leading to allergy symptoms. Normally, allergy symptoms are not life-threatening. But some people have a severe allergic reaction that can lead to anaphylaxis. Even if you or your child have had only a mild allergic reaction in the past, there's still a risk of future anaphylaxis.

A number of allergens can trigger anaphylaxis, depending on what you're allergic to.
Common anaphylaxis triggers include:

• Certain medications, especially penicillin
• Foods, such as peanuts, tree nuts (walnuts, pecans), fish, shellfish, milk and eggs
• Insect stings from bees, yellow jackets, wasps, hornets and fire ants

Less common causes of anaphylaxis include:

• Latex
• Muscle relaxants used during general anesthesia
• Exercise

Anaphylaxis triggered by exercise varies from person to person. In some people, aerobic activity, such as jogging, triggers anaphylaxis. In others, less intense physical activity, such as walking, can trigger a reaction. Eating certain foods before exercise or exercising when the weather is hot, cold or humid has also been linked to anaphylaxis in some people. Talk with your doctor about any precautions you should take when exercising.

Anaphylaxis symptoms are sometimes caused by aspirin, other nonsteroidal anti-inflammatory drugs — such as ibuprofen (Advil, Motrin, others) and naproxen sodium (Aleve, Midol Extended Relief) — and the intravenous (IV) contrast used in some X-ray imaging tests. Although similar to allergy-induced anaphylaxis, this type of reaction isn't triggered by allergy antibodies.

If you don't know what triggers your allergy attack, your doctor may do tests to try to identify the offending allergen. In some cases, the cause of anaphylaxis is never identified. This is known as idiopathic anaphylaxis.

Complications:

 An anaphylactic reaction can be life-threatening when a severe anaphylactic attack occurs; it can stop breathing or stop your heartbeat. In this case, you'll need cardiopulmonary resuscitation (CPR) and other emergency treatment right away.


Treatments and drugs:

During an anaphylactic attack, an emergency medical team may perform cardiopulmonary resuscitation (CPR) if you stop breathing or your heart stops beating. You may be given medications including:

• Epinephrine (adrenaline) to reduce your body's allergic response
• Oxygen, to help compensate for restricted breathing
• Intravenous (IV) antihistamines and cortisone to reduce inflammation of your air passages and improve breathing
• A beta agonist (such as albuterol) to relieve breathing symptoms

What to do in an emergency
If you're with someone who is having an allergic reaction and shows signs of shock caused by anaphylaxis, act fast. Signs and symptoms of shock caused by anaphylaxis include pale, cool and clammy skin, weak and rapid pulse, trouble breathing, confusion, and loss of consciousness. Even if you're not sure symptoms are caused by anaphylaxis, take the following steps immediately:

• Call 911 or emergency medical help.
• Check the person's pulse and breathing and, if necessary, administer CPR or other first-aid measures.
• Give medications to treat an allergy attack, such as an epinephrine autoinjector or antihistamines, if the person has them.

Using an autoinjector
Many people at risk of anaphylaxis carry an autoinjector. This device is a combined syringe and concealed needle that injects a single dose of medication when pressed against your thigh. Always be sure to replace epinephrine before its expiration date, or it may not work properly.

Be sure you know how to use the autoinjector. Also, make sure the people closest to you know how to administer the drug — if they're with you in an anaphylactic emergency, they could save your life. Medical personnel called in to respond to a severe anaphylactic reaction also may give you an epinephrine injection or another medication to treat your symptoms.

Long-term treatment
If your anaphylactic reaction is triggered by insect stings, you may be able to get a series of allergy shots (immunotherapy) to reduce your body's allergic response and prevent a severe reaction in the future.

Unfortunately, in most other cases there's no way to treat the underlying immune system condition that can lead to anaphylaxis. But you can take steps to prevent a future attack — and be prepared in the event one does occur.

• Avoid your known allergy triggers as much as you can.
• You may need to carry self-administered epinephrine. During an anaphylactic attack, you give yourself the drug using an autoinjector (EpiPen, EpiPen Jr or Twinject).
• Your doctor may recommend taking prednisone or antihistamines.