Allergies and Anaphylaxis

Anaphylaxis is a severe allergic reaction that needs to be treated right away. If you have an anaphylactic reaction, you need an epinephrine (adrenaline) shot as soon as possible, and someone should call 911 for emergency medical help. Left untreated, it can be deadly.

Video Transcript

Thomas Chacko, MD Allergist

THOMAS CHACKO: The difference between allergies and anaphylaxis-- anaphylaxis can be the life-threatening type, meaning-- allergies, when people think about it, could be sneezing, hayfever, or even asthma. But anaphylaxis could be those symptoms as well as more, including hypotension-- or low blood pressure; wheezing to the point where you can't breathe; loss of consciousness or passing out. So anaphylaxis is life-threatening or very severe allergies. If it's a food allergy, most people discover that when they're younger once they had the first or second time of introduction to, let's say, peanuts or some type of tree nut. Possibly other sources of anaphylaxis, like insect sting, like, you know, people could be life-threatening allergic to bee stings. That could be later because you might not have been stung by a bee earlier or it could be your second time that you got stung that you had this significant life-threatening anaphylaxis. So it depends on what you're allergic to. Most of the time you don't grow out of anaphylaxis. With food allergies, about 20% to 25% of patients may grow out of it. That means the vast majority-- 80-- 80% or so-- will keep it. So most people do not outgrow anaphylaxic reactions. I would say the mortality rates are not going up, meaning we are better now at identifying anaphylaxis and people are much more aware. So people aren't dying as much from anaphylaxis. Unfortunately, there still are deaths but not as much in the past because we're better at being aware of it as well as treating it.

Epinephrine can reverse the symptoms within minutes. If this doesn't happen, you may need a second shot within half an hour. These shots, which you need a prescription to get, come pre-filled and in ready-to-use pens.

You shouldn’t take an antihistamine for an anaphylactic reaction.

Anaphylaxis is rare, and most people recover from it. But it's important to tell your doctor about any drug allergies you have before any kind of medical treatment, including dental care. It’s also a good idea to wear a medical alert bracelet or pendant or carry a card with information about your allergy.

If you've had an anaphylactic reaction before, you have a higher risk of having another one. You also have a higher risk if you have a family history of anaphylaxis or have asthma.


The first signs of an anaphylactic reaction may look like typical allergy symptoms: a runny nose or a skin rash. But within about 30 minutes, more serious signs appear.

There is usually more than one of these:

Some people also remember feeling a "sense of doom” right before the attack.

As many as 1 out of every 5 people may have a second anaphylactic reaction within 12 hours of the first. This is called a biphasic anaphylaxis.


Epinephrine is the most effective treatment for anaphylaxis, and the shot should be given right away (usually in the thigh). If you’ve had an anaphylaxis reaction before, you should carry at least two doses of epinephrine with you at all times.


Epinephrine expires after about a year, so make sure your prescription is up to date. If you have an anaphylactic reaction and the pen has expired, take the shot anyway.

When medical personnel arrive, they may give you more epinephrine. If you’re not able to breathe, they may put a tube down your mouth or nose to help. If this doesn’t work, they might do a kind of surgery called a tracheostomy that puts the tube directly into your windpipe.

Either in the ambulance or at the hospital, you may need fluids and medications to help you breathe. If the symptoms don't go away, doctors may also give you antihistamines and steroids.

You probably will need to stay in the emergency room for several hours to make sure you don't have a second reaction.

After the initial emergency is over, see an allergy specialist, especially if you don't know what caused the reaction.


Anaphylaxis happens when you have an antibody, something that usually fights infection, that overreacts to something harmless like food. It might not happen the first time you come in contact with the trigger, but it can develop over time.

In children, the most common cause is food. For adults, the main cause is medication.

Typical food triggers for children are:

  • Peanuts
  • Shellfish
  • Fish
  • Milk
  • Eggs
  • Soy
  • Wheat

Common food triggers for adults are:

  • Shellfish
  • Tree nuts (walnuts, hazel nuts, cashews, pistachios, pine nuts, and almonds)
  • Peanuts

Some people are so sensitive that even the smell of the food can trigger a reaction. Some are also allergic to certain preservatives in food.

Common medication triggers are:

  • Penicillin (more often following a shot rather than a pill)
  • Muscle relaxants like the ones used for anesthesia
  • Aspirin, ibuprofen, and other NSAIDs (non-steroidal anti-inflammatory drugs)
  • Anti-seizure medications

Anaphylaxis also can be triggered by a few other things. But these aren’t as common:

  • Pollen, such as ragweed, grass, and tree pollen
  • Stings or bites from bees, wasps, yellow jackets, hornets, and fire ants
  • Latex, found in hospital gloves, balloons, and rubber bands


Some people can have an anaphylactic reaction if they breathe in latex.

Some can have a reaction to a combination of things:

  • Breathe in birch pollen and eat apple, raw potato, carrots, celery, or hazelnut
  • Breathe in mugwort pollen and eat celery, apples, peanuts, or kiwi
  • Breathe in ragweed pollen and eat melons or bananas
  • Touch latex and eat papaya, chestnuts, or kiwi

In rare cases, it can be triggered by 2 to 4 hours of exercise after eating certain foods or by exercise on its own.

Anaphylactic reactions usually start within minutes of contact with the trigger, but they can also happen an hour or more later.

Some people never figure out what caused their reactions.

WebMD Medical Reference Reviewed by Carol DerSarkissian on June 14, 2020



American Academy of Allergy, Asthma & Immunology: "Anaphylaxis."

American Academy of Pediatrics: "Anaphylaxis."

American College of Asthma, Allergy & Immunology: "Anaphylaxis."

Asthma and Allergy Foundation of America: "Anaphylaxis: A Severe Allergic Reaction."

Cleveland Clinic: "Anaphylaxis."

Food Allergy Research & Education: "About Anaphylaxis."

World Allergy Organization: "Anaphylaxis: Synopsis."

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