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ER or urgent care?

Allergic reaction: when to go to the ER

A severe allergic reaction, called anaphylaxis, can start within seconds or minutes 1. If you have an epinephrine auto-injector, use it right away and call 911 1 2. Mild reactions, like a few hives or an itchy nose, are different 2.

Find the nearest ER In an emergency, call 911. Updated November 15, 2026; every fact links to its source below.
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Go to the ER or call 911 if

  • Trouble breathing, wheezing, throat tightness or a hoarse voice 3 1
  • Swelling of the lips, tongue, face or eyes 1
  • Dizziness, fainting, or feeling faint 3
  • Hives with vomiting, belly cramps, or any of the signs above 3 2
  • More than one mild symptom from different parts of the body, which counts as severe 2

After using epinephrine, go to the ER even if you feel better: symptoms can return, so stay at least 4 hours 2. A second reaction can happen 12 to 24 hours later 4. Don’t rely on antihistamines for a severe reaction 2.

If you’re not sure, go to the ER. Find the nearest ER.

When urgent care can help

A severe reaction belongs in the ER, not urgent care 5 6. Mild hives may need no treatment, or a provider may suggest an antihistamine 7. Urgent care clinics treat insect bites 6.

Insect stings

For pain, redness and swelling only at the sting, scrape out the stinger, ice the area, and take an antihistamine for itching 8. At the first sign of anaphylaxis, use epinephrine, call 911 and get to emergency care 8.

Ongoing mild allergies? See a provider online

For everyday allergy symptoms like sneezing, an itchy nose or itchy eyes, with none of the signs above, an online visit is one way to talk about treatment. Never use an online visit for a reaction that is getting worse. You’ll leave ER.com when you continue. More on Allergies online.

See a provider online

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Common questions

Allergic reaction: when to go to the ER, answered.

General information, not medical advice or a diagnosis.

When should I go to the ER for an allergic reaction?
Go, or call 911, for trouble breathing, throat tightness, swelling of the lips or tongue, fainting, or hives with vomiting 3 1.
Do I need the ER after using an EpiPen?
Yes. Go to the ER and stay at least 4 hours, because symptoms can come back 2.
Can urgent care treat an allergic reaction?
Mild reactions, yes. A severe reaction with trouble breathing or swelling belongs in the ER 5.
See a provider online now Only if it’s not an emergency. ER.com may earn a commission through affiliate links, at no added cost to you.

Related conditions

Allergies · Hay fever · Insect bites · Rash

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Sources

  1. MedlinePlus: Anaphylaxis (reviewed Jan. 20, 2026)
  2. FARE (Food Allergy Research & Education): Recognize and respond to anaphylaxis (2025)
  3. American Academy of Allergy, Asthma & Immunology: Anaphylaxis (June 18, 2026)
  4. American College of Allergy, Asthma and Immunology: Anaphylaxis (reviewed Mar. 24, 2025)
  5. MedlinePlus: Choosing the right place to get health care (reviewed July 15, 2026)
  6. American College of Emergency Physicians: Emergency care, urgent care, what’s the difference? (PDF)
  7. MedlinePlus: Hives (reviewed Apr. 1, 2025)
  8. American College of Allergy, Asthma and Immunology: Insect sting allergies (reviewed June 28, 2023)

Last updated November 15, 2026. General information from the sources above, not medical advice or a diagnosis, and not a substitute for being seen. If you’re not sure whether something is an emergency, go to the ER or call 911.

This is not for emergencies.

For life-threatening symptoms, severe chest pain, trouble breathing, or immediate danger, call 911 or go to the nearest emergency department.