What Is Anaphylaxis? How to Spot and Treat Life-Threatening Allergic Reactions

These days, almost everyone is familiar with allergies in some way. Peanuts aren’t allowed in schools and some people are terrified of bee stings. And everywhere you look you see labels that say, “may contain eggs” or “manufactured in a facility that processes tree nuts.” But what do these things actually mean? 

Is a serious allergic reaction — anaphylaxis — as bad as it sounds? And what should you do if you have one or see someone else having one? 

What is anaphylaxis?

Anaphylaxis is a severe allergic reaction that has an unpredictable nature. It’s important to know about because it can happen quickly and progress into a dangerous and even fatal condition — anaphylactic shock. 

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It starts when your immune system responds to an allergen, like a food, as if it’s a foreign or harmful object. The body produces an extra amount of immune cells — mast cells and basophils — which then release inflammatory chemicals like histamine. Within minutes, you can start to see symptoms. 

Anaphylaxis can happen even if you’ve never reacted to something before. And someone who has had mild reactions to an allergen can go on to have a more severe reaction the next time.

What are common triggers of anaphylaxis?

According to the American College of Allergy, Asthma and Immunology, the most common causes of anaphylaxis are foods, insect stings, medications, and latex. Here are some examples:

• Food: peanuts, tree nuts (walnuts, almonds, and pecans), fish, shellfish, cow’s milk, and eggs

• Latex: in disposable gloves, intravenous tubes, syringes, adhesive tapes, or catheters

• Medications: penicillin, aspirin, muscle relaxants, and anesthesia

• Insect stings: from bees, wasps, hornets, yellow jackets, or fire ants 

• Contrast: for medical imaging purposes

• Exercise: triggered by physical activity

• Idiopathic: meaning the cause is never identified

What are the first symptoms and signs of  anaphylactic shock?

When someone has an anaphylactic reaction, it can start out with a rash or a feeling that something “just isn’t right.” But it can progress quickly into: 

• Trouble breathing

• Hives

• Itching

• Runny nose

• Tightness of the throat

• Nausea or abdominal pain

• Diarrhea

• Dizziness

• A feeling of doom

Skin symptoms (such as hives, itching, and swelling) are usually the first to show up, and they’re the most common sign of anaphylaxis. Other symptoms, such as runny nose or vomiting, may follow as the reaction gets worse.

The most severe cases affect the respiratory and cardiovascular systems. The airways start to close, blood pressure starts to drop, and the heart must then work harder. This is anaphylactic shock — a dangerous and life-threatening situation.

Symptoms of anaphylaxis can be mild, and they may go away on their own. But most anaphylactic reactions will require treatment. It’s difficult to predict if or how quickly they will get worse. Symptoms might be delayed for several hours. It’s also possible to have another reaction hours after the first one ends.  

What does anaphylactic shock look like? 

Shock happens when the circulatory system no longer functions properly. So organs and tissues don’t get the blood they need, and the body tries to correct that. At first, there may be no signs at all. But, over time, shock causes:

• A fast heart rate

• A change in blood pressure

• Wheezing or gasping for air

• Fainting

• Clammy skin

How do you treat anaphylaxis?

Epinephrine (also known as adrenaline) is the primary treatment for anaphylaxis. It can be self-injected. If you have known anaphylaxis, you should carry epinephrine with you at all times. 

Epinephrine works in a few different ways: 

• It constricts blood vessels, which may help with low blood pressure. 

• It decreases swelling in soft tissues and helps open the airways. 

• It decreases the release of inflammatory chemicals from mast cells and basophils. 

People often need more than one dose of epinephrine, so it’s important to get help immediately.

How should you respond to an anaphylactic reaction? 

Here are some tips for what to do:

• Call 911. If you think you or someone around you is having an anaphylactic reaction, you should get help immediately by calling 911 and/or going to the nearest emergency room. 

• Administer epinephrine. Give an Epipen or an equivalent auto-injector  (like AuviQ) as soon as possible. Many people will need more epinephrine minutes or hours after the first treatment. So, even if symptoms improve or go away, still seek help. If you don’t have an EpiPen, it’s even more important to get medical attention right away to prevent anaphylactic shock.

• Monitor breathing. Watch for changes in breathing. You may give CPR, but remember that the airway can swell shut, so you should get emergency help. 

• Get a medical evaluation. There’s a risk of symptoms getting worse or another reaction happening minutes to hours later. So it’s important to be evaluated and monitored in the emergency department. 

How can you prevent anaphylactic shock?

Unfortunately, if you’ve had an anaphylactic reaction, you’re likely to have another, and it could be more severe next time. 

The best way to prevent another anaphylactic reaction is to avoid the trigger. If you have a food allergy, always read the labels. It’s important to know your trigger(s) and to be able to recognize the signs and symptoms of anaphylaxis. This way you can feel it coming on and know what to do. 

If you start to notice symptoms in yourself or someone else, don’t hesitate to use an auto-injector. When used early in anaphylaxis, epinephrine can prevent progression to anaphylactic shock.

If you have an auto-injector:

• Be sure you know how to use it. 

• Keep it up to date (replace it if it expires).

• Keep it with you at all times. 

• Make sure your friends and family know about your allergy. 

• Make sure your friends and family know about your auto-injector, where you keep it, and how to use it (in case they need to give you the medication).

Consider wearing a bracelet that clearly states what your allergy is. It lets a bystander or healthcare worker know about your allergy if you’re not able to speak for yourself.

Finally, when it comes to allergic reactions, an allergist can help. Allergists are doctors who specialize in allergies, asthma, and other immune system problems. They can help you identify your trigger(s), run some more tests, and talk with you about treatment options.

Why trust our experts?

Written by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

Reviewed by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

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