Harmful Spiders in the U.S.

There are more than 3,000 types of spiders in the United States of America. Chances are you've seen plenty of spiders in various locations ranging from your home to wooded areas. Luckily, out of such a large number of spider varieties, there are very few types that are truly potentially harmful to humans. Some spiders cannot even break human skin, and others' venom does not normally trigger reactions. On the extreme side of the spectrum, some spiders' bites can cause serious complications and even death.

  1. Brown Recluse

    • The brown recluse is found across the United States but is more predominant in the south. These spiders gain their name from the fact that they are reclusive, preferring cool, dark areas like woodpiles, rocks, storage areas and even shoes left unattended. Adult brown recluses range between 1/4 and 3/4 of an inch long. A tell-tale marking is a dark violin shape that appears on the back, starting just below the head and pointing toward the abdomen. Symptoms of a brown recluse bite include pain at the bite site, stinging, nausea, abdominal cramping, sweating, weakness, excessive salivation and sometimes coughing. Quick administration of anti-venom is usually very successful. Left untreated, a bite from a brown recluse leads to the rotting of skin, which may require surgical excision in order to prevent the spread of infection.

    Black Widow

    • Like their brown recluse relatives, the black widow spider is another venomous spider that prefers secluded living areas. These spiders are about 1/2 inch in length, although females can grow to 1 1/2 inches. The female black widow possesses a distinguishing red hourglass marking on its abdomen. A bite from a black widow usually causes intense pain at the site of the bite, coupled with muscle spasms, nausea, elevated blood pressure and breathing difficulties. These bites usually are only fatal for young children or babies, along with older adults or adults whose immune systems are compromised.

    Other, Less-Harmful Spiders

    • While black widows and brown recluses share the spotlight of being the deadliest American spiders, there are some others whose bites can cause concern. Hobo spiders and black house spiders cause painful bites that may be accompanied by severe headache, nausea, dizziness and fatigue. Mouse spiders have large fangs that produce a very painful bite. Several other spiders will bite when provoked, but the bite usually only causes a painful bite without other serious symptoms. Allergic reactions in a small number of individuals also can worsen the effects of a spider bite.

    First Aid

    • If you are bitten by a spider, seek medical attention immediately. If it is safe to do so, capture the spider so doctors can positively identify the species and administer the appropriate treatment or anti-venom. Victims of spider bites should lie down and stay as still as possible until medical help arrives. If you are attending a victim of a spider bite, clean the wound with soap and water. Apply a cold compress to the bite area and wrap a compression bandage slightly above the bite if the bite is located on a limb. Elevate a limb to slow the spread of venom. Keep the person as still and calm as possible.