Key takeaways:
Anaphylaxis is a serious allergic reaction that can lead to anaphylactic shock.
Anaphylactic shock is life-threatening because blood pressure drops dangerously low, leading to lack of blood flow to critical organs.
Common symptoms of anaphylaxis include hives, itching, trouble breathing, vomiting, diarrhea, and dizziness.
Epinephrine is the primary treatment, which is why people with certain allergies should carry an auto-injector with them at all times.
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These days, almost everyone is familiar with allergies in some way. But there’s a wide range of types and symptoms of allergies. For some, this could be itchy eyes and a runny nose during pollen season. For others, this could be a rapid throat swelling and difficulty breathing after a bee sting.
In this article we talk about the most severe and life-threatening type of allergy — anaphylaxis and anaphylactic shock. We’ll explain what these are, how you know when they’re happening, and what to do.
What is anaphylaxis and anaphylactic shock?
Anaphylaxis is a severe allergic reaction that has an unpredictable nature. It’s important to know about it because anaphylaxis can happen quickly and progress into a dangerous and even fatal condition — anaphylactic shock.
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. It’s impossible to predict when this might happen.
Anaphylaxis vs. anaphylactic shock
Anaphylactic shock is a severe version of anaphylaxis. It happens when anaphylaxis affects the cardiovascular system. This leads to a dangerous drop in blood pressure, which prevents adequate blood flow throughout the body. This means that critical organs — like your brain and heart — don’t get enough oxygen. This can quickly become fatal.
Not all cases of anaphylaxis will progress to anaphylactic shock. And treatment of anaphylaxis prevents this from happening. (We cover treatment more in a section below.)
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 (like 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: This means the cause is never identified.
What are the first symptoms and signs of anaphylaxis and 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 common symptoms of anaphylaxis include:
Hives
Itching
Runny nose
Tightness of the throat
Swelling of the face, lips, tongue, or throat
Trouble breathing
Nausea or abdominal pain
Diarrhea
Dizziness
A feeling of doom
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?
The most severe cases of anaphylaxis — anaphylactic shock — affect the respiratory and cardiovascular systems. The airways start to close, blood pressure starts to drop, and the heart must then work harder.
Shock happens when the circulatory system no longer functions properly. At first, there may be no signs at all. But as it progresses, shock causes:
A fast heart rate
A low blood pressure
Wheezing or labored breathing
Fainting or altered mental state
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, even if you feel better after using it.
Treatment for anaphylactic shock
Epinephrine is also the main treatment for anaphylactic shock. But people often need repeated or higher doses of it to treat shock. Often this means a continuous and steady infusion of epinephrine into a vein.
In addition to epinephrine, the treatment for anaphylactic shock may include:
Breathing support with oxygen or a mechanical ventilator
Intravenous (IV) fluids
Additional medicines to increase the blood pressure
Most people with anaphylactic shock will need to be treated in an intensive care unit (ICU).
How should you respond to an anaphylactic reaction?
Here are some tips for what to do when someone near you is having an anaphylactic reaction:
Call 911: If you think you or someone around you is having an anaphylactic reaction, call 911 right away. This is better than driving someone to an ER yourself, as they may need treatment en route to the hospital.
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 get help.
Monitor them closely: Watch for changes in their mental status and breathing. If they lose consciousness, check for a pulse and start CPR.
Even with milder symptoms — or if they get better after an EpiPen — it’s important to always 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 anaphylaxis and 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.
Frequently asked questions
No, anxiety doesn’t cause anaphylaxis. That being said, anaphylactic events can often cause intense feelings of anxiety or panic. And this sense of panic may occur before any other obvious symptoms of anaphylaxis. So anaphylactic reactions can unfortunately sometimes be mistaken for panic attacks.
Yes, anaphylactic shock can lead to a heart attack. But not in the traditional way that most people have heart attacks. Anaphylactic shock leads to dangerously low blood pressure, which affects blood flow to all the organs in the body. This includes the heart muscle. And when the heart muscle doesn’t get enough blood (and oxygen), this can lead to a heart attack.
Yes, anaphylactic shock can lead to brain damage. But only in very severe cases that don’t receive prompt treatment. This is because anaphylactic shock happens when the blood pressure drops so low it affects blood supply to critical organs — like the brain. And if the blood pressure remains low for a prolonged period of time, brain cells start to die. This can lead to both temporary and permanent brain damage.
No, anxiety doesn’t cause anaphylaxis. That being said, anaphylactic events can often cause intense feelings of anxiety or panic. And this sense of panic may occur before any other obvious symptoms of anaphylaxis. So anaphylactic reactions can unfortunately sometimes be mistaken for panic attacks.
Yes, anaphylactic shock can lead to a heart attack. But not in the traditional way that most people have heart attacks. Anaphylactic shock leads to dangerously low blood pressure, which affects blood flow to all the organs in the body. This includes the heart muscle. And when the heart muscle doesn’t get enough blood (and oxygen), this can lead to a heart attack.
Yes, anaphylactic shock can lead to brain damage. But only in very severe cases that don’t receive prompt treatment. This is because anaphylactic shock happens when the blood pressure drops so low it affects blood supply to critical organs — like the brain. And if the blood pressure remains low for a prolonged period of time, brain cells start to die. This can lead to both temporary and permanent brain damage.
The bottom line
Anaphylaxis and anaphylactic shock are life-threatening. If you know you have an allergy, be sure to keep your epinephrine auto-injector up to date and with you at all times. At the first signs of anaphylaxis, administer epinephrine and call for emergency medical help.
Why trust our experts?
References
American College of Allergy, Asthma & Immunology. (2025). Anaphylaxis.
Barg, W., et al. (2010). Exercise-induced anaphylaxis: An update on diagnosis and treatment. Current Allergy and Asthma Reports.
