Anaphylaxis Guide: Symptoms, Causes, and Treatment

What is anaphylaxis?

Anaphylaxis is a severe allergic reaction involving the whole body. It can start and progress very quickly. And it can be very dangerous — even fatal. 

Like with an allergy, anaphylaxis starts when your immune system mistakes a harmless substance (like a food) for a harmful invader. The body then reacts with an overblown immune response to the perceived invader. The cells of the immune system release large amounts of inflammatory chemicals, like histamines. This reaction can happen within the span of minutes.

Anaphylaxis can be unpredictable. It can happen if you’ve never reacted to something before. It can also happen even if you’ve only had mild reactions to a substance in the past.

Anaphylaxis is most common in people who are allergic to: 

• Peanuts

• Tree nuts

• Bee stings

• Certain medications 

It’s also more likely if you’ve had it before. 

Allergies

Written by Mandy Armitage, MD

Signs and symptoms of anaphylaxis

The symptoms of anaphylaxis can come on quickly, usually within minutes of contact with a trigger. Sometimes, though, they can be delayed and occur over an hour after exposure.

The first signs can vary. It can start out with something obvious, such as a hives-like rash. Or it can be more subtle, like a feeling that something “just isn’t right.” But it can progress quickly into the following symptoms:

• Tightness of the throat

• Swelling of the face, lips, tongue, or throat

• Difficulty breathing

• Hives and itching

• Runny nose

• Fast heartbeat

• Nausea or vomiting

• Abdominal pain 

• Diarrhea

• Dizziness or lightheadedness

• Feeling of doom

• Confusion and anxiety

Skin symptoms (such as hives, itching, and/or swelling) are usually the first to show up — but not always. Other symptoms, such as a runny nose or vomiting, may follow as the reaction gets worse. It might not be obvious what’s going on, especially if the person has never had anaphylaxis before. 

The most severe cases affect the respiratory and cardiovascular systems. The airways start to close, making it hard to breath and get oxygen into the body. It can also cause blood pressure to drop, forcing the heart to work harder to keep blood flowing. This is a dangerous, life-threatening situation called anaphylactic shock.

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

Written by Mandy Armitage, MD

What causes anaphylaxis?

Allergies and anaphylaxis tend to run in families, but genetics aren’t the whole picture. Anaphylaxis is more likely in people who also have allergies and asthma. If you’ve had severe allergic reactions in the past, then you’re at higher risk for anaphylaxis. 

According to the American College of Allergy, Asthma, and Immunology, the most common causes of anaphylaxis are:

• Foods

• Insect stings

• Medications

• Latex 

When these otherwise harmless substances cause an allergic reaction, they’re called “allergens.”

Examples of allergens include:

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

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

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

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

• Contrast dye: sometimes used for medical imaging

Anaphylaxis can also be triggered by substances that aren’t allergens, such as exercise, cold, or heat. And, sometimes, the cause of anaphylaxis is never determined (called idiopathic anaphylaxis).

Wondering If You Have Allergies or Asthma? It Could Be Allergic Asthma

Written by Fonda Jiang, MD

How is anaphylaxis diagnosed?

Anaphylaxis is usually diagnosed in an emergency setting. The diagnosis is based on signs and symptoms, not one particular test. 

Blood tests can look for the presence of some inflammatory chemicals called tryptase and histamine, which may be elevated during anaphylaxis. But these aren’t necessary for diagnosis. 

If you have known allergies, it may help to see an allergist. Allergists are healthcare professionals who specialize in allergies, asthma, and other immune system problems. They can help you identify your trigger(s). They can also help you understand your treatment options and your risk of anaphylaxis.

It’s important to know that allergy test results don’t predict the severity of future reactions. In other words, anyone’s at risk for anaphylaxis, regardless of what the tests show.

Allergy Tests: What Are They and How Can You Get One?

Written by Frank Schwalbe, MD

Treatment and medications for anaphylaxis

You should always seek emergency medical care for anaphylaxis. If it’s not treated quickly, it can be life-threatening. 

The main treatment for anaphylaxis is epinephrine. It comes in an injectable device (called an auto-injector). This can be used quickly when severe allergy occurs. An auto-injector can be used only once.

People with severe allergies should carry their epinephrine auto-injectors on them at all times and know how to use them. 

Epinephrine devices are only available by prescription. They include:

• EpiPen

• EpiPen Jr

• Adrenaclick

• Symjepi

• Auvi-Q

Here’s what to do if you see someone experiencing anaphylaxis:

• Administer epinephrine: Give epinephrine as soon as possible if an auto-injector is available. 

• Call 911: This is preferable to driving someone to the nearest ER. Since anaphylaxis can progress quickly, it’s better to have emergency personnel who can provide treatment along the way. 

• Lie down: Sitting upright is OK if it helps their breathing, but do it slowly. Otherwise, lay down and elevate the legs. This will help with blood flow to the brain and heart. Avoid sudden standing or sitting.

• Make sure they get a medical evaluation: Do this even if they start to feel better. There’s a risk of symptoms getting worse or another reaction happening minutes to hours later. 

Someone who has had an anaphylactic attack always needs to go to the hospital afterward — even if they’re feeling better. They may need more epinephrine once the first shot wears off. Also, they could need other life-saving treatments that can only be given in a hospital.

How Much Are EpiPens? Cost-Cutting Tips, Alternatives, and More

Written by Charlene Rhinehart, CPA

Preventing anaphylaxis

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. For example, if you have a food allergy, always read menus and labels. It’s important to know what your trigger is. Also, you should be able to recognize the signs and symptoms of anaphylaxis. That way, you can feel it coming on and know what to do. 

You may also consider wearing a bracelet and carrying a wallet card that clearly states what your allergy is. These items let bystanders or healthcare workers know about your allergy if you’re not able to speak for yourself.

If you have an epinephrine auto-injector, here are some tips:

• 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).

If you don’t have an epinephrine auto-injector, and you think you might need one, contact your healthcare team right away. Epinephrine is safe, effective, and life-saving.

Here’s How to Get an Epipen Refill Without Seeing a Doctor in Person

Written by Ana Gascon