Understanding Anaphylaxis - the Basics

What Is Anaphylaxis?

Anaphylaxis is a sudden, severe allergic reaction that occurs when you are exposed to a substance that your body was sensitized to during a previous 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, especially around the face and throat. The chemicals also act on the lungs, causing an asthmatic reaction -- that is, causing the lung's airways to constrict, thus making breathing very difficult.

In some cases, anaphylaxis may have mild symptoms, causing only hives and itching. But it can be deadly. 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 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 occurs usually within minutes of exposure to the allergen and almost always within two hours. The most severe cases may be fatal just 10 minutes after exposure. Sometimes symptoms may disappear and then return later.

If administered in time, an injection of epinephrine (adrenaline) may reverse the condition 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 United States). Immediate treatment can help ensure full recovery.