“Anaphylactic shock is the most severe form of anaphylaxis,” says Inderpal Randhawa, MD, a board-certified allergist and pulmonologist and the founder of the Food Allergy Institute in Long Beach, California. “It happens when your body’s immune system overreacts to a trigger, called an allergen, releasing chemicals that cause a sudden drop in blood pressure and narrowing of airways. This can stop your heart or breathing if not treated immediately.”

• Foods — most commonly peanuts and tree nuts (e.g., almonds, cashews, and walnuts), eggs, milk, sesame, and shellfish
  
• Insect stings, such as a bee, hornet, or wasp sting
• Latex
• Medications, such as antibiotics, chemotherapy drugs, iodine-containing contrast agents used in CT scans and MRIs, and nonsteroidal anti-inflammatories
  

• Trouble breathing (e.g., wheezing, tight throat, and a hoarse voice)
• Swelling of the face, lips, and/or tongue
• Rapid heartbeat, cardiac arrest, or arrhythmia
• Flushing, hives, or itching
• Dizziness or fainting (due to plummeting blood pressure)
• Cramping, diarrhea, or vomiting
• Confusion or a feeling of impending doom
  

The defining factor of anaphylactic shock is cardiovascular involvement. It often causes a rapid drop in blood pressure, leading to symptoms such as dizziness or fainting, says Dr. Randhawa.

Anaphylactic shock can be potentially life threatening if not addressed immediately. The first line of treatment is epinephrine, administered via an auto-injector or nasal spray. “Epinephrine reverses swelling, restores breathing, and supports blood pressure,” says Randhawa.

Because of the cardiovascular collapse associated with anaphylactic shock, you may lose consciousness, says Lighvani. For that reason, it’s important to let your family and friends know how to help you in an emergency situation. “We usually advise caretakers to have the patient lie flat and elevate the legs while you wait for emergency services. That posture increases blood flow toward the brain,” says Lighvani.

• Advanced age
• Certain medications, such as ACE inhibitors and beta-blockers
• Comorbidities, such as asthma, cardiovascular disease, food allergies, and mast cell disorders
• Delayed access to epinephrine
• Exercising after eating a food you’re allergic to

Even if you’ve never had a severe allergic reaction, that doesn’t mean you’ll never need to worry about anaphylaxis or anaphylactic shock. “People can develop severe, life-threatening allergies at any age,” says Randhawa. “Adult-onset food allergies, for example, are becoming more recognized, and reactions can be just as serious as those that start in childhood.”

Similarly, just because allergic reactions have been mild for you in the past doesn’t mean they’ll continue to be. “Some people have unpredictable reactions — mild one time, severe the next,” says Randhawa. “However, once you’ve had a severe reaction, you’re at higher risk for future severe reactions, so it’s critical to be prepared with epinephrine.”

The bottom line: If you have an allergy that can result in anaphylaxis, always carry two epinephrine devices, and get emergency medical care right away if you come in contact with the allergen.

• Anaphylactic shock causes a sudden and dangerous drop in blood pressure, making immediate treatment with epinephrine crucial. It’s also important to call 911 right away.
• Anaphylactic shock is different from regular anaphylaxis in that it always involves the cardiovascular system, leading to dizziness or a loss of consciousness.
• You may be at risk of going into anaphylactic shock if you have another condition, such as asthma; are on medications such as beta-blockers; are of an advanced age; or other factors.