Medically Reviewed By:
Dr. Ayesha Malik, MD (Allergy & Emergency Medicine Specialist)
Medically reviewed on October 25, 2025
Dr. Malik is a certified emergency physician specializing in anaphylaxis, skin infections, and allergic reactions to insect bites and stings.
Quick Answer (Featured Snippet Box)
Go to the ER immediately if an insect bite causes difficulty breathing, dizziness, throat swelling, severe pain, rapid spreading redness, or pus-filled blisters. These are signs of a serious allergic reaction or infection that requires emergency medical care.
When to Go to the ER for an Insect Bite
Most insect bites cause mild redness, itching, or swelling that fades within a few days. However, some bites trigger dangerous allergic reactions or infections.
According to the Centers for Disease Control and Prevention (CDC), knowing when to seek emergency care can prevent life-threatening complications.
Key Signs You Should Go to the ER
You should seek immediate emergency care if you notice any of the following symptoms after an insect bite:
| Emergency Sign | What It Means |
|---|---|
| Difficulty breathing or wheezing | Possible anaphylaxis (severe allergic reaction) |
| Swelling of the lips, eyes, or throat | Airway obstruction risk |
| Severe, spreading redness or swelling | Possible skin infection or cellulitis |
| Fever or chills | Infection spreading to bloodstream |
| Dizziness or fainting | Blood pressure drop from allergic shock |
| Pus-filled blister or necrotic wound | Bacterial infection or spider bite necrosis |
| Uncontrollable pain or numbness | Venom-related nerve involvement |
➡️ Note: These symptoms can develop quickly — sometimes within minutes — after a bite or sting.
Common Medical Complications from Insect Bites
While many bites are harmless, certain species like wasps, fire ants, spiders, and bees can cause severe immune or bacterial responses.
1. Allergic Reaction or Anaphylaxis
Anaphylaxis is a life-threatening systemic reaction that can cause airway closure, low blood pressure, and shock.
Immediate epinephrine injection and ER evaluation are required.
Read more on WHO: Insect Stings and Allergies.
2. Skin Infection (Cellulitis or Abscess)
Scratching can introduce bacteria into the wound, leading to redness, heat, swelling, and pus.
According to the Mayo Clinic, cellulitis must be treated with prescription antibiotics.
3. Necrotic or Venomous Reactions
Some spiders (e.g., brown recluse or black widow) and ants inject venom that can destroy tissue or affect the nervous system.
If the bite area becomes black, ulcerated, or severely painful, go to the ER immediately.
First Aid Before Going to the ER
While waiting for emergency help, follow these steps to slow reaction progression:
Stay calm and keep the affected area still.
Remove stinger or visible insect parts with a scraping motion (do not squeeze).
Wash the area with soap and water to prevent infection.
Apply a cold compress to reduce pain and swelling.
Elevate the limb if swelling is significant.
If available, take an oral antihistamine to ease itching.
Use your EpiPen immediately if you have one and experience breathing issues.
When to Go to the ER for a Child’s Insect Bite
Children are more vulnerable because their bodies react faster and more intensely to toxins.
Take your child to the ER if they experience:
Crying or screaming from pain that won’t stop
Facial swelling or trouble breathing
Hives spreading rapidly across the body
Fever or red streaks around the bite
According to the American Academy of Pediatrics (AAP), never delay emergency care in such cases.
Frequently Asked Questions (FAQs)
1. Should I go to the ER if an insect bite keeps swelling?
Yes, if swelling continues to expand after 24 hours or spreads to other areas, it could indicate infection or allergic inflammation.
2. Can I treat an infected insect bite at home?
Mild cases may respond to topical antibiotics, but pus, fever, or severe redness require medical evaluation.
3. What is the difference between an allergic reaction and infection?
An allergic reaction causes itching and hives, while infection causes pain, heat, and pus.
4. When should I use an EpiPen for a bite or sting?
Use immediately if you experience difficulty breathing, dizziness, or throat tightness, then go to the ER.
5. How long does it take for normal insect bites to heal?
Most heal in 3–5 days, though scratching can extend healing time and increase infection risk.
Conclusion
In summary, you should go to the ER for an insect bite if symptoms involve trouble breathing, spreading swelling, pus, dizziness, or severe pain.
While most bites are mild, ignoring severe reactions can be dangerous.
By staying alert, using your EpiPen when necessary, and getting prompt medical help, you can prevent life-threatening complications and ensure faster recovery.
Always trust your instincts — when in doubt, seek professional care immediately.
