What Is Anaphylaxis?
Anaphylaxis is a sudden, severe allergic reaction that often occurs when you are exposed to a substance that your body was sensitized to during a previous exposure, but anaphylactic reactions can occur without a history of prior exposure.
The life-threatening reaction causes a sudden release of chemicals, including histamines, from cells in the blood and the body's tissues. These chemicals dilate the blood vessels, lowering blood pressure, and they cause the blood vessels to leak fluid, leading to hives and swelling (angioedema), especially around the face and throat. The chemicals also act on the lungs, constricting the airways, causing an asthmatic reaction thus making breathing very difficult.
In some cases, anaphylaxis may initially present with only mild symptoms, such as hives and itching, but it can quickly progress to a deadly reaction. Blood pressure can drop severely, leading to loss of consciousness. Swelling of the throat and airways can cause difficulty breathing, speaking, and swallowing. Anaphylaxis is a medical emergency.
What Causes Anaphylaxis?
Theoretically, almost any protein substance can provoke anaphylaxis.
However, the most common causes of anaphylactic shock are:
- Foods, such as peanuts
- Tree nuts, particularly almond, walnut, hazel, Brazil, and cashew nuts
- Shellfish, especially shrimp and lobster
- Dairy products
- Eggs
- Insect stings, such as wasps, bees, ants
- Latex
- Medications
Less common causes of anaphylaxis include:
- Exercise, after consumption of an allergy-provoking food.
Anaphylaxis usually occurs within minutes of exposure to the allergen and almost always within two hours. The most severe cases may be fatal within a few minutes of exposure. Sometimes symptoms may disappear and then return later.
If administered in time, an injection of epinephrine (adrenaline) may arrest the progression of anaphylaxis by quickly constricting blood vessels to help circulation, stopping swelling around the face and throat, and relaxing smooth muscles in the lungs to open up the airways. Because anaphylaxis can progress so quickly, the first signs of reaction should be taken seriously. Do not wait to see how serious the reaction may become: Call for emergency help immediately (call 911 in the U.S.) and administer epinephrine if appropriate. Delayed administration of epinephrine has been shown to be most important determining factor for poor patient outcomes with anaphylatic reactions. Immediate treatment can help ensure full recovery.
