This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
First Aid for Allergic Reactions and Anaphylaxis
An allergic reaction occurs when the body's immune system overreacts to a harmless substance, such as food, medication, or insect venom. Reactions can range from mild skin irritation to anaphylaxis, a life-threatening emergency requiring rapid intervention. Recognizing symptoms early and knowing how to administer epinephrine can save a life.
Quick Summary
Treat mild symptoms with oral antihistamines, but immediately administer an epinephrine auto-injector and call emergency services if any breathing difficulty, throat tightness, or widespread symptoms occur.
Important Medical Disclaimer
This guide is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with qualified healthcare providers for medical concerns.
Step-by-Step Guide
Assess symptoms and identify signs of anaphylaxis
Quickly determine whether the reaction is mild or severe. Mild reactions typically involve isolated hives, mild itching, or nasal congestion. Severe reactions, known as anaphylaxis, involve two or more body systems or any breathing difficulty, throat tightness, tongue swelling, dizziness, vomiting, or confusion.
Important: Do not wait to see if severe symptoms improve on their own; anaphylaxis can progress to respiratory failure or shock within minutes.
Administer an epinephrine auto-injector immediately
If the person has a known severe allergy or displays any signs of anaphylaxis, help them use their epinephrine auto-injector immediately. Press the injector firmly into the outer mid-thigh at a 90-degree angle until it clicks, and hold it in place according to the device instructions (typically 3 to 10 seconds). Epinephrine works rapidly to open airways, reduce throat swelling, and stabilize blood pressure.
Important: Administer epinephrine without delay; late administration of epinephrine is the primary risk factor for fatal allergic reactions.
Call emergency medical services
Dial 911 or your local emergency number immediately after administering epinephrine, or right away if you suspect anaphylaxis and do not have an auto-injector. Clearly inform the dispatcher that the patient is having a severe allergic reaction or anaphylaxis, and report the exact time epinephrine was delivered. Keep the used auto-injector to hand over to the emergency medical crew.
Position the person correctly
Lay the person flat on their back and elevate their legs approximately 12 inches to support blood flow to vital organs. If they are having severe difficulty breathing, allow them to sit up slightly, or place them on their side in the recovery position if they feel dizzy, faint, or are vomiting. Never force a person in anaphylaxis to stand or walk.
Important: Do not allow the person to stand up suddenly, as this can cause a catastrophic drop in blood pressure.
Remove the allergen trigger if safe and possible
Eliminate further exposure to the allergen if it can be done safely. For insect stings, scrape the stinger off the skin using a fingernail or stiff card rather than squeezing it with tweezers to avoid releasing more venom. If the reaction is due to a topical irritant, gently wash the skin with cool running water, but never induce vomiting if an allergen was swallowed.
Monitor vitals and prepare a second dose if needed
Continuously monitor the person's airway, breathing, and responsiveness while waiting for medical personnel. If symptoms do not improve or worsen after 5 to 15 minutes, administer a second dose of epinephrine using a new auto-injector in the opposite thigh. If the person stops breathing or loses a pulse at any point, begin CPR immediately.
Manage mild reactions with oral antihistamines
If the reaction is truly mild—strictly limited to localized hives or minor itching with no throat, lung, or gastrointestinal involvement—an oral second-generation antihistamine like cetirizine or loratadine may be given. Apply a cool, damp compress to soothe itchy skin. Monitor the individual closely for at least 2 to 4 hours to ensure symptoms do not progress into a systemic reaction.
Important: Antihistamines treat hives and itching, but they cannot treat or reverse airway swelling or low blood pressure during anaphylaxis.
Frequently Asked Questions
What is the difference between a mild allergic reaction and anaphylaxis?
Can I give an antihistamine instead of epinephrine during a severe reaction?
What should I do if I am unsure whether a reaction requires epinephrine?
Why must a person go to the emergency room even if epinephrine resolves their symptoms?
Sources & References
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This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed October 19, 2026. · Read our editorial policy