When to see a doctor about a bite
The vast majority of bites need soap, a cold pack and patience. A short list of findings changes that: trouble breathing or throat tightness (emergency), spreading redness with fever (same day), and an expanding rash days after a tick bite (same week).
Call emergency services now
- Difficulty breathing, wheeze, or a tight throat.
- Swelling of the lips, tongue or face.
- Dizziness, fainting or collapse.
- Widespread hives appearing away from the bite.
- A sting inside the mouth or throat.
- Severe cramping in the abdomen, back or chest after a suspected black widow bite.
- Roving eye movements, slurred speech or twitching after a scorpion sting, especially in a child.
These are anaphylaxis or systemic envenomation. If an adrenaline auto-injector has been prescribed, use it first and call afterwards.
Be seen the same day
- Redness that is spreading, hot and painful, particularly with a red streak.
- Fever, chills or feeling generally unwell after a bite.
- Pus, or a wound breaking down.
- A bite near the eye, or a rapidly swelling hand or face.
- Any suspected black widow or brown recluse bite.
- Fever within two weeks of a tick bite — Rocky Mountain spotted fever is time-critical.
Be seen this week
- An expanding rash 3 to 30 days after a tick bite.
- A tick that was attached longer than 36 hours.
- Bites that keep appearing with no cause found, especially with household members itching.
- A bite that has not improved at all after a week.
- Delayed hives or stomach upset a few hours after eating red meat following a lone star tick bite.
Who should have a lower threshold
Infants and young children, adults over 65, pregnant people, anyone with a weakened immune system, and anyone with a previous severe reaction to a sting. For these groups, "watch and wait" is worth shortening.
What to bring
Photographs taken over several days, the date of the bite, the location and habitat, and the insect itself if you have it. Timing and geography change the differential more than the appearance of the mark does.
Common questions
My whole forearm swelled after a wasp sting — is that anaphylaxis?
A large local reaction is uncomfortable and can last days, but it is not anaphylaxis. The emergency signs are breathing difficulty, faintness and symptoms away from the sting.
Should I go in for a tick bite with no symptoms?
Usually not, but note the date and species, and be seen if a rash or fever appears in the following month.
Is an insect bite ever an emergency in a child?
Yes — any breathing difficulty, a scorpion sting with neurological signs, or a rapidly spreading infection.
Get a photo assessment in the app
Everything above is free to read. The app adds what a page cannot: point your camera at the bite and get an assessment of the most likely cause, a severity read, and a day-by-day care plan — including the specific signs that mean you should be seen.
iPhone and iPad. Free to download.