Everything To Know About Anaphylactic Shock
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Medically reviewed by Jurairat J. Molina, MD
Anaphylactic shock is a complication of anaphylaxis—a severe, life-threatening allergic reaction that happens suddenly after exposure to an allergen. Anaphylaxis occurs when your immune system perceives a substance (allergen) as a threat and overreacts. As a result, your immune system releases a flood of chemicals into your body that triggers symptoms like a skin rash, itching, stomach pain, vomiting, and trouble breathing.
Anaphylaxis can quickly progress to anaphylactic shock if left untreated, causing a sudden drop in your blood pressure and swollen, narrowed airways. Keep in mind: anaphylactic shock is a medical emergency that requires immediate treatment. Without proper intervention, the condition can become fatal within 15 minutes.
Between 2% and 5% of people in the U.S. have experienced anaphylaxis. Anyone can develop anaphylaxis, but it's most common in people with a history of allergies. The most common allergens that can trigger anaphylaxis include certain medicines, foods, insect stings, and latex.
Symptoms
Symptoms of anaphylaxis typically begin quickly after exposure to an allergen. Your symptoms can develop within minutes, but sometimes it can take up to several hours, also known as biphasic reaction. Anaphylaxis and anaphylactic shock symptoms can affect the heart, lungs, mouth, skin, and gastrointestinal system. For some people, symptoms of anaphylaxis are initially mild and progressively worsen. Others may experience sudden, severe symptoms that rapidly progress to anaphylactic shock.
Skin Symptoms
Exposure to an allergen will usually cause some changes in your skin. These symptoms may include:
Respiratory Symptoms
Symptoms affecting the respiratory system—including the throat and lungs—are hallmark signs of anaphylaxis. If you're exposed to something you're allergic to, you might notice the following symptoms:
Tightness in the throat
Hoarse voice
Gastrointestinal Symptoms
Some people experiencing anaphylaxis may develop gastrointestinal symptoms. Your gastrointestinal (GI) tract is the part of your body that connects your mouth to your anus—and all the organs between them. If you experience GI symptoms, you may have:
Neurological Symptoms
Some people who have experienced anaphylaxis report feeling a sense of impending doom or a feeling as if something terrible is about to happen. Other neurological symptoms include:
Shock Symptoms
If you do not receive immediate treatment for anaphylaxis, it can progress to anaphylactic shock and cause more serious symptoms, such as:
Difficulty breathing
Sudden drop in blood pressure
Rapid heart rate
Swollen tongue
Trouble swallowing
Confusion
Weakness
Loss of consciousness
Sukhman Rekhi, Health Editor
"When I went into anaphylaxis in 2017, my initial symptoms were mild: some swelling on my face and a cough. After four days, the swelling got so bad that I couldn't open my eyes anymore. Two of my best friends rushed me to the ER hours later when my heart rate shot up to 195 beats per minute. Luckily, I was admitted immediately and a team of healthcare professionals helped save my life. One of the doctors told me that if I was even a few minutes late, I may not have survived. That was a scary thing to hear—so if you're experiencing symptoms, seek medical care as soon as possible."
Causes
Anaphylactic shock is a complication of a severe allergic reaction (anaphylaxis) that occurs when the body's immune system mistakenly identifies a normally harmless substance (an allergen) as a threat.
When a person with allergies comes into contact with an allergen, the immune system overreacts and produces immunoglobin E (IgE) antibodies. IgE antibodies travel to cells throughout the body, triggering the release of histamine and other chemicals to fight the allergen. These chemicals affect multiple body systems and organs, causing a cascade of symptoms that affect the skin, nose, throat, eyes, lungs, heart, and gastrointestinal system.
Any allergen can trigger a severe allergic reaction and lead to anaphylactic shock. About 90% of all anaphylactic reactions occur due to certain foods, insect stings or bites, and medications. The most common triggers include:
Foods: Peanuts, eggs, shellfish, cow's milk, walnuts, and pecans
Medication: Penicillin, aspirin, non-steroidal anti-inflammatory drugs (e.g., ibuprofen)
Insect venom: Stings or bites from bees, wasps, fire ants, yellow jackets, and hornets
Latex: Found in objects like disposable gloves, syringes, intravenous tubes, catheters, adhesive tapes, and condoms
Risk Factors
Anyone can experience anaphylaxis in response to an allergen, including those who previously only had mild allergic reactions, such as a rash, watery eyes, or a runny nose. But certain risk factors increase your chances of anaphylactic shock, including:
A personal history of allergies
A family history of anaphylaxis
Living with asthma
Exposure to environmental allergens, which are more common among people who work in the food industry or hospital settings
Diagnosis
Anaphylaxis can quickly progress to anaphylactic shock, which is a potentially life-threatening medical emergency. When a person in anaphylactic shock arrives at the hospital, healthcare providers work quickly to evaluate their vital signs, including blood pressure, heart rate, and respiratory rate. They will also look for signs of anaphylactic shock, including hives, flushed or clammy skin, a swollen tongue, wheezing, or a visible struggle to breathe.
Healthcare providers may ask what allergen you may have been exposed to, how quickly symptoms developed, and whether you administered epinephrine (such as an EpiPen) before you came to the hospital. While not always necessary, blood tests measuring histamine and mast cell tryptase (MCT) levels in the bloodstream (chemicals the body releases in response to an allergen) can help confirm the diagnosis of anaphylactic shock.
Treatment
Anaphylaxis and anaphylactic shock require immediate treatment with epinephrine (adrenaline) at the first signs of a severe allergic reaction. Epinephrine reverses the severe allergic reaction by opening the airways and raising blood pressure.
Anaphylactic Shock Is a Medical Emergency
If you or someone you know has an allergic reaction and shows symptoms of anaphylaxis, use a self-injectable epinephrine pen (EpiPen) and call 911 or go to the nearest emergency room for additional treatment. Many people with allergies carry an EpiPen at all times, but not everyone does. If you don't have an EpiPen but are experiencing symptoms, it's essential to get medical attention right away.
Epinephrine is the only treatment that effectively reverses anaphylaxis and anaphylactic shock, and repeated doses may be necessary. At the hospital, healthcare providers may administer additional epinephrine intravenously (IV). Some healthcare providers use other medications for symptom relief, such as:
Antihistamines: While not a substitute for epinephrine, antihistamines relieve skin-related symptoms, such as hives, itching, and swelling.
Corticosteroids: Some healthcare providers administer corticosteroid drugs intravenously (through an IV) to reduce inflammation and prevent symptoms from flaring up again. However, this practice is increasingly less common as evidence suggests corticosteroids may be more harmful than helpful.
Bronchodilators: These medications help open narrow airways, making breathing easier.
It's also important to note that even after you receive the proper treatment, sometimes your symptoms will slowly start to improve but won't go away immediately. It can take a few days for swelling or hives to completely subside.
Supportive Care
People who experience anaphylactic shock require a hospital stay to monitor their condition. Biphasic anaphylaxis, which occurs in up to 20% of people recovering from anaphylaxis, is when symptoms return hours after recovery with no additional exposure to the allergen. Hospitalization allows healthcare providers to closely monitor your vital signs, including your heart rate, respiratory rate, blood-oxygen level, and blood pressure, to ensure your continued recovery.
Supportive care while in the hospital may include:
Supplemental oxygen: Oxygen therapy helps improve blood oxygen levels in people with breathing difficulties
Intravenous fluids: Intravenous fluids can help prevent dehydration and its associated complications, such as dizziness or seizures
Airway management: If your airways are severely swollen and narrow, intubation may be necessary to help you breathe
How to Prevent Anaphylactic Shock
Avoiding exposure to known allergens is the best way to prevent anaphylaxis and anaphylactic shock. Your healthcare provider will work with you to develop effective strategies for avoiding allergens. Avoidance strategies vary depending on the type of substance you might be allergic to:
Foods: Carefully read food labels, ask restaurants about food ingredients and preparation practices, and inform your workplace or your child's school about the allergy to avoid exposure.
Medications: Tell your healthcare providers if you have a history of anaphylaxis in response to certain medications, such as penicillin. They will prescribe safe alternatives. Some people wear medical alert jewelry (e.g., bracelets, necklaces) that list known allergens to alert first responders to their allergies in an emergency.
Insect stings: You may need to avoid wearing perfume or scented lotions, wear shoes at all times outdoors, and avoid brightly colored or floral-patterned clothing during the most active insect seasons (e.g., summer and early fall)
Along with avoiding potential triggers, you can lower your risk of anaphylactic shock by:
Carrying an epinephrine auto-injector, such as an EpiPen, in your purse, car, or bag at all times
Developing an emergency plan that outlines the steps to take in case of an allergic reaction and sharing this plan with family members, friends, coworkers, or caregivers
Regularly visiting your healthcare provider, such as an allergist, to monitor your condition, ensure you are up-to-date on the latest treatments, and have ongoing education and support
Complications
Anaphylactic shock is a severe medical emergency that requires immediate treatment to prevent organ failure and death. Anaphylactic shock can block your airways, preventing you from breathing and getting the oxygen your body needs. This reaction also causes a sudden drop in blood pressure, causing cardiac arrest (stopping the heart), which cuts off the supply of blood and oxygen to the body's vital organs. Without proper treatment, you may experience kidney failure, brain damage, or death.
A Quick Review
Anaphylactic shock is a serious, life-threatening complication of anaphylaxis—a severe allergic reaction that can occur within seconds to minutes of exposure to an allergen. Symptoms of anaphylactic shock can include difficulty breathing, rapid heart rate, clammy skin, confusion, seizures, and loss of consciousness.
If you or someone you know are experiencing symptoms, it's essential to seek medical attention right away. Prompt treatment with epinephrine is the only way to reverse the symptoms of anaphylactic shock and prevent death.
Frequently Asked Questions
Does anaphylactic shock go away on its own?
No, anaphylactic shock does not go away on its own. It is a severe, life-threatening complication of anaphylaxis and requires immediate emergency medical care.
When should you go to the ER for an allergic reaction?
Go to the ER or call 911 for an allergic reaction if you experience difficulty breathing, hives, facial swelling, dizziness, fainting, rapid heart rate, or a loss of consciousness.
Can anaphylaxis be stopped with Benadryl?
Benadryl (diphenhydramine) is an antihistamine that can help relieve the symptoms of mild allergic reactions, but it is ineffective in treating anaphylaxis. Epinephrine (adrenaline) is the only medication that can reverse the symptoms of anaphylaxis and prevent a fatal reaction.
Sukhman Rekhi is an editor at Health. She experienced anaphylaxis in 2017 while she was still in college. She initially hoped that her symptoms would subside on their own, which is why she delayed seeing a healthcare provider immediately. Now that she has more knowledge about this life-threatening reaction, she urges you to seek medical care as soon as you can if you've been exposed to an allergen.
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