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Allergic reactions can cause a host of symptoms. Most symptoms, such as rash, watery eyes, or runny nose, are often mild or moderate. But sometimes, you can have a severe and potentially fatal allergic reaction called anaphylaxis.

What Is Anaphylaxis?

Anaphylaxis is an acute or immediate severe allergic reaction. About one in 50 people in the U.S. will experience anaphylaxis in their lifetime. That’s according to the Asthma and Allergy Foundation of America (AAFA).

Though rare, rates of anaphylaxis have doubled in the United States over the past 20 years, according to StatPearls. And each year, 1,500 people die from anaphylaxis.

Anaphylaxis is a medical emergency that requires immediate medical care. Left untreated, the disorder causes rapid damage to your body and is often fatal. It can cause you to stop breathing or suffer anaphylactic shock.

What is anaphylactic shock?

Anaphylactic shock sometimes serves as an interchangeable term for anaphylaxis. But it’s not always the same thing. Here’s what it means.

Anaphylactic shock is a type of distributive shock or vasodilatory shock. Anaphylaxis causes your blood vessels to dilate or widen, which in turn causes a steep drop in your blood pressure. When this happens, it stops needed blood flow to your heart, brain, and kidneys, causing significant damage or even organ failure.

What is a biphasic reaction?

Even if you get treated for anaphylaxis, you might have a second anaphylactic reaction up to 12 hours after your first reaction. This is a biphasic reaction. That’s why you need to go to the emergency room, even after using epinephrine — the only medication that stops an anaphylactic reaction.

Getting help ASAP starts with knowing what causes anaphylaxis and what it looks like.

What Causes Anaphylaxis?

During an allergic reaction, your body’s immune system views something as harmful and releases histamine and other chemicals to fight it. Most of the time, your body releases the right amount of these chemicals, so symptoms are mild or moderate. But sometimes, your body can release too many of these chemicals, causing severe symptoms.

Anaphylaxis signs and symptoms

Anaphylaxis can affect many different organ systems in your body. Symptoms of anaphylaxis often come on suddenly and quickly get worse, often within minutes. They can include:

• Airway or respiratory problems, such as wheezing, trouble breathing, shortness of breath, hoarse throat, fullness or “a lump in the throat,” and difficulty swallowing.
• Gut or gastrointestinal problems, such as bloating, diarrhea, vomiting, stomach pain, or cramps.
• Heart or cardiovascular problems, such as dizziness, decreased blood pressure, increased heart rate, weak pulse, and feeling faint or fainting.
• Neurological problems, such as agitation, convulsions, or a sharp change in mental status. These may also come accompanied by feelings of impending doom or dread, like something bad is about to happen.
• Skin reactions, such as itching, rash, or hives. You can also get angioedema, swelling beneath your skin that can affect your eyelids, ears, face, mouth, tongue, hands, and feet.

Common anaphylaxis triggers

Allergens are the most common trigger of anaphylaxis. They include:

• Foods. In children, the leading cause of anaphylaxis is food allergies, especially eggs, milk, peanuts, soy, and wheat. That’s according to the AAFA. Adults’ most common food allergies are peanuts, shellfish, and tree nuts.
• Insect bites or stings. Stinging insects like bees, hornets, wasps, fire ants, yellow jackets, and spongy moth caterpillars can cause anaphylaxis.
• Latex. Direct contact or breathing in latex particles can cause anaphylaxis in some people. Balloons, condoms, latex gloves, and latex pillows and mattresses contain latex.
• Medication is the leading cause of anaphylaxis in adults, according to the AAFA. Common medication triggers include antibiotics (especially penicillin and sulfa/sulfonamides), aspirin, ibuprofen, and insulin.
• Physical activity. In rare cases, vigorous physical activity combined with other factors can cause anaphylaxis. These co-factors can include extreme temperatures, seasonal changes, alcohol, medications, or eating certain foods before exercise.

Risk factors for anaphylaxis

Anyone at any age can develop anaphylaxis. You’re at an increased risk of anaphylaxis if you:

• Have experienced anaphylaxis before.
• Have allergies to foods, insect stings, medicines, and other triggers.
• Have asthma.

If you have asthma and allergies, your allergist will go over the differences between difficulty breathing caused by asthma and anaphylaxis. When in doubt, treat yourself with epinephrine.

Treatment for Anaphylaxis

Epinephrine injection is the most effective and important treatment for anaphylaxis. If this is your first episode of anaphylaxis, you will get epinephrine in the emergency room. An epinephrine autoinjector can also give you this medication.

An epinephrine autoinjector is an intramuscular injection that you give yourself or that someone else gives you. It works quickly to stop the allergic reaction. You should only inject an epinephrine autoinjector into the middle of the outer side of your thigh or upper leg.

If you have a history of allergic reactions to specific allergens, your treatment plan will include a prescription for epinephrine injectors. Oral antihistamines don’t work or replace epinephrine shots. Only epinephrine injections can stop a severe allergic reaction and prevent anaphylactic shock.

When Should You Get Medical Help for Anaphylaxis

If you experience the first sign of anaphylaxis after exposure to your allergen or trigger, immediately administer an epinephrine shot.

Then call 911 to get medical care or have someone drive you to the nearest emergency room.

You need emergency care even if you feel better and even if you gave yourself an epinephrine injection. In 20% of cases, anaphylaxis returns eight to 11 hours after the initial reaction, according to StatPearls. This second reaction can also prove fatal.

Anaphylaxis can get worse quickly, often within an hour of exposure to the trigger. Half of all people who die from anaphylaxis die within the first hour, according to StatPearls. The faster your symptoms start, the more severe the disease process happens in your body.

Preventing Anaphylaxis

Figuring out your triggers can help you avoid anaphylaxis in the future. Your doctor can refer you to an allergist — a specialist who treats allergies. They can run allergy tests to pinpoint what causes you to have an allergic reaction.

Allergists are often able to determine the cause. Sometimes, you may have anaphylaxis that doesn’t result from a known trigger. If your allergist cannot identify your trigger, they diagnose the condition as idiopathic anaphylaxis.

To prevent anaphylaxis:

• See a specialist to identify your triggers and get an action plan.
• Always keep your epinephrine autoinjector with you in case of an allergic reaction.
• Know and avoid your triggers.
• Recognize the symptoms of anaphylaxis and start epinephrine autoinjector treatment at the first sign. Then call 911.
• Wear medical identification, noting your condition and your allergy triggers.