A spider bite often appears like other insect bites, with a red inflamed bump on the skin that may be itchy or painful, explains Mayo Clinic. While harmless spider bites do not usually produce other symptoms, the bite of a brown recluse or black widow may require medical treatment.
Redness that spreads away from the bite, a discoloration surrounding the bite that looks similar to a bull's-eye and drainage from the bite are signs that can indicate a potentially dangerous spider bite.
There are only a few spiders in the world with the ability to penetrate human skin. While there may be no sign of a bite on the skin, victims of a black widow bite may experience rigid, painful muscles within eight hours of the bite. They may also experience severe abdominal pain, nausea and trouble breathing, reports KidsHealth.
A bite from a brown recluse consists of a red blister in the center of a bluish discoloration of the skin and swelling or redness around the bite, and it often results in joint stiffness or pain. Victims may also experience nausea, body rash and fever, explains KidsHealth.
Treatment for most spider bites, including bites from a black widow or brown recluse, involves cleaning the bite with mild soap and water and applying cold packs to reduce inflammation. Over-the-counter medications are effective to manage pain and swelling. It's also necessary to monitor the site for signs of infection, notes Mayo Clinic.
Anaphylaxis, which is a severe allergic reaction, is the biggest concern after a bug bite, explains About.com. A person with post-bite symptoms such as wheezing, shortness of breath or hives should call 911 for emergency care.