If you start to experience symptoms that are not just at the site of the bite or sting (and you don't have a history of severe reactions), seek medical attention. These symptoms (systemic symptoms affect the whole body) may progress to fatal anaphylactic shock.
Hives are the most common systemic symptom. They appear as irregular, raised, red blotchy areas on the skin and are very itchy. If hives are the only systemic symptom present, they are often treated at home with an antihistamine.
If the bite appears infected (redness with or without pus, warmth, fever, or a red streak that spreads toward the body), see a doctor.
If you don't know what bit you, it is important to keep watching the area closely to be sure it does not become infected. Call your doctor if there is an open wound, which may suggest a poisonous spider bite.
People who have a history of severe reactions should go to the nearest hospital's emergency department after a bite or sting if they experience any symptoms. Those who have no history of severe reactions should also go to the emergency department if they have any of the following symptoms :
- Wheezing
- Shortness of breath
- Chest tightness or pain
- Sensation of the throat closing or difficulty speaking or swallowing
- Faintness or weakness
- Infection (If the wound appears infected and you are not able to reach your doctor, seek care at a hospital.)
Exams and Tests
The diagnosis of a reaction to a bite or sting is usually obvious from the history. The doctor will perform a physical examination to look for effects of the bite or sting on various parts of the body. Examination of the skin, respiratory system, cardiovascular system, and oral cavity are particularly important.
The above information thankfully comes from the Webmd.com at the following link.