Anaphylaxis and Anaphylactic Shock
anaphylactic shock (A-nuh-fih-LAK-tik shok): A severe and sometimes life-threatening immune system reaction to an antigen that a person has been previously exposed to. The reaction may include itchy skin, edema, collapsed blood vessels, fainting, difficulty in breathing, and death. -- NCI Dictionary
Anaphylaxis is a severe "systemic" reaction, which means that the whole body is affected, It often occurs within minutes of exposure. The fact that eating a very common food can result in this very rare-but-life-threatening symptom (especially among small children) is the primary reason for peanut allergy's widespread publicity.
It is important to know that an anaphylactic reaction can only occur if the victim has been previously exposed to the offending agent. For example, someone who is allergic to bee stings might have a strong reaction the first time he or she is stung, but will not have an anaphylactic reaction.
A wide range of substances – including insect venom, pollen, latex, and various foods and drugs – can cause anaphylaxis. In sensitive people, anaphylaxis can occur within minutes of contact with an allergen. It may also occur up to several hours after exposure.
Anaphylaxis not only causes breathing difficulty and sometimes respiratory blockage, it can also result in a sudden blood pressure drop which may result in a heart attack.
Anaphylactic shock is the most severe and serious form of anaphylaxis. It is an urgent medical emergency requiring immediate treatment, chiefly because:
- Bronchial tissue in the lungs begin to expand, causing the airways to contract.
- Breathing turns to wheezing and becomes extremely difficult; soon the person may pass out. Skin, lips and nail beds may turn blue.
- Dilating blood vessels leak water into the surrounding tissue which begins to swell, particularly in the face and neck. Blood pressure drops as well due to blood vessel dilation.
Left untreated, anaphylactic shock can prove fatal just ten minutes following exposure, but prompt and effective medical care can save the patient's life. Usually, a shot of epinephrine (adrenaline) is administered, which constricts the blood vessels, slows or stops the tissue from swelling, and allows the airways to expand.
An epinephrine injection is the only known and proven treatment for severe anaphylaxis. Epinephrine is a hormone commonly known as adrenaline.
Symptoms of anaphylaxis may include:
- Hives or other epidermic swelling
- Breathing difficulty
- Throat tightness / choking feeling
- Nausea & Vomiting
- Stomach pain & Diarrhea
- Faintness or dizziness
- Low blood pressure
- Rapid heart beat
- Extreme anxiety
- Cardiac arrest
Food anaphylaxis is the leading known cause of anaphylactic reactions treated in U.S. hospitals. It is estimated that there are 30,000 anaphylactic reactions to foods treated in emergency departments and 150 to 200 deaths each year. Peanuts, tree nuts, fish, and shellfish account for most of these severe cases.
- American College of Allergy, Asthma & Immunology, "Anaphylaxis"
- Food Allergy and Anaphylaxis Network
- "Molecular Mechanism of Anaphylactic Shock Decoded," Science Daily, 2009
- eMedicineHealth: Severe Allergic Reaction
Function of epinephrine
Epinephrine for anaphylaxis