Most insect bites and stings cause a small itchy or painful bump from a local reaction to saliva or venom. A few people develop a large local reaction, a skin infection or a body-wide allergic reaction that can become anaphylaxis.
Key symptoms
- Itchy red bump or wheal at the bite site
- Pain or burning right after a sting
- Large local reaction: swelling over 10 cm that peaks in 1 to 2 days
- Hives away from the bite, throat tightness or wheeze suggest allergy
What you find on exam
- Bumps, often in clusters or lines (bedbugs, fleas) or with a central puncture
- Stinger left in the skin after a honeybee sting
- Size of swelling and whether it crosses a joint
- Signs of infection: warmth, pus, spreading redness, fever
- Vital signs, airway, lungs and skin to look for a systemic reaction
Tests
- Usually no tests are needed
- Culture if there is pus or an abscess
- Referral for venom allergy testing after a systemic reaction
- Tick bite: judge Lyme disease risk by region and time the tick was attached
Treatment basics
- Remove a stinger quickly by scraping or pulling; wash with soap and water
- Cold compress, an oral antihistamine such as cetirizine, and a topical steroid for itch
- Large local reaction: antihistamine, ice, elevation and sometimes a short course of oral prednisone
- Antibiotics only for true infection, not for swelling alone
- Anaphylaxis: IM epinephrine right away, then prescribe an auto-injector
Red flags
- Trouble breathing, throat swelling, wheeze or fainting
- Spreading redness, fever or red streaks up the limb
- Growing target-shaped rash or fever after a tick bite
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Related guides
Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; NASEMSO National Model EMS Clinical Guidelines. Written by Making Synapses. Making Synapses is not affiliated with these organizations.