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Date Published: July 20, 2026
Anaphylaxis is a severe allergic reaction that can become life-threatening in minutes. This medical emergency affects multiple body systems at the same time. It can make breathing difficult, cause a dangerous drop in blood pressure and lead to shock without prompt treatment.
Recognizing the signs of anaphylaxis and responding quickly are critical. Fast action improves outcomes until advanced medical help arrives.
Sign up for the American Red Cross Anaphylaxis & Epinephrine Auto-Injector and Nasal Spray Online to learn the signs and symptoms of anaphylaxis and how to care for a person having a severe allergic reaction.
Anaphylaxis occurs when the immune system overreacts to a substance it mistakenly sees as harmful. This reaction causes the body to release chemicals that can affect breathing, circulation and other important functions.
Some people know they have severe allergies. Others experience anaphylaxis without any previous history of a serious reaction. Anaphylaxis is often associated with food allergies, but it can also be triggered by medications, insect stings, latex and other allergens.
Food allergies are one of the leading causes of anaphylaxis. Even a small amount of a food allergen can cause a severe reaction. Common foods that cause allergic reactions include:
Stings from bees, hornets, wasps and other insects can trigger anaphylaxis in people with insect venom allergies. While many people experience only temporary pain and swelling from a sting, others may develop symptoms that affect breathing and circulation.
Certain medications can cause severe allergic reactions. A reaction may occur after taking a medication for the first time. In some cases, a person develops an allergic reaction after previously taking the medication without any problems.
Some common examples of medications that cause anaphylaxis include:
Latex allergies can occur after contact with products such as gloves, balloons and some medical supplies. For some individuals, exposure causes mild symptoms. Others may experience a severe allergic reaction.
Although rare, some people experience anaphylaxis during or after physical activity. Certain foods or medications may increase the risk when combined with exercise.
Anyone can experience anaphylaxis, including people who have never had a severe allergic reaction before.
People at higher risk include:
While these factors may increase risk, anaphylaxis remains unpredictable. Learning how to recognize the signs of anaphylaxis and respond appropriately benefits everyone.
In many emergencies, bystanders are the first people available to help. Training provides the knowledge and confidence to take action while waiting for emergency medical services.
Anaphylaxis is a medical emergency. If you suspect someone is experiencing anaphylaxis, act immediately.
Symptoms can worsen rapidly, so do not wait to see whether they improve on their own. A person may experience one symptom or several symptoms at the same time:
Epinephrine works quickly to address the most dangerous symptoms of anaphylaxis. It is the first-line treatment for anaphylaxis. If the person has a prescribed epinephrine auto-injector or nasal spray, use it as directed as soon as symptoms appear.
This medicine helps open the airways, improves breathing and supports blood pressure. Prompt treatment can help slow or stop the progression of the reaction.
Even if symptoms improve after epinephrine is administered, emergency medical evaluation is still necessary. Symptoms can return after the initial reaction appears to improve, making medical monitoring important.
Help the person lie flat on their back with their legs elevated, if possible. This position promotes circulation. If breathing is compromised, allow them to sit up in a position that makes breathing easier. If they are vomiting, place them on their side.
Watch for changes in breathing or responsiveness while waiting for emergency responders. If the person becomes unresponsive and is not breathing normally, begin CPR if you are trained to do so.
Some people may have instructions from their healthcare provider to administer a second dose of epinephrine if symptoms last or return. Follow the person's emergency action plan and the instructions provided with the medication.
During anaphylaxis, prompt treatment with epinephrine is critical. American Red Cross First Aid/CPR/AED courses teach you how to recognize anaphylaxis and respond confidently in emergencies. Through hands-on training and real-world scenarios, you learn skills to administer epinephrine safely and provide care while waiting for advanced medical help to arrive.
Being prepared also means having the right supplies available when you need them. Keeping a well-stocked first aid kit at home, work, school and while traveling support emergency response efforts.
Many people keep antihistamines on hand for seasonal allergies and mild allergic reactions. While these medications can help relieve some symptoms, they are not a substitute for epinephrine during anaphylaxis.
Antihistamines take longer to work and do not treat the most dangerous symptoms. Relying on antihistamines during anaphylaxis may delay lifesaving treatment.
Antihistamines can relieve mild symptoms such as:
However, antihistamines do not:
When anaphylaxis occurs, every minute matters. Being prepared means knowing how to:
Your prompt response during an anaphylaxis emergency can save a life.
The free First Aid mobile app by the American Red Cross puts expert advice for common emergencies like anaphylaxis in the palm of your hand — from the latest First Aid and CPR techniques to the nearest hospital location. Stay up to date on your lifesaving skills.
Or text: "GETFIRST" to 90999
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