Occupational Safety and Health Administration OSHA

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Protect Yourself! Workers may be exposed to

Black Widow Spider

The black widow belongs to a group of spiders commonly known as cobweb spiders. The characteristic hourglass is located on the underside of the abdomen. Female black widows are dangerous and can bite and inject toxic venom.


  • The female black widow is normally shiny black, with a red hourglass marking (see photo) on the underside of the abdomen.
  • The abdominal marking may range in color from yellowish orange to red and its shape may range from an hourglass to a dot.
  • The body of an adult black widow female is about 1/2 inch long.


The black widow is commonly found in the following places:

  • Outdoors - woodpiles, rubble piles, under stones, in hollow stumps, and in rodent burrows, privies, sheds and garages.
  • Indoors - undisturbed, cluttered areas in basements and crawl spaces.


  • The bite of the black widow may be painful or it may go unnoticed.
  • The skin may display one or two bite marks with local swelling. Pain usually progresses from the bite site and eventually to the abdomen and back.
  • Severe cramping or rigidity may occur in the abdominal muscles.
  • Symptoms may include nausea, profuse perspiration, tremors, labored breathing, restlessness, increased blood pressure and fever.
  • The pain from the bite will usually persist for the first 8-12 hours.
  • Symptoms may continue for several days.


  • Wear a long-sleeved shirt, hat, gloves, and boots when handling boxes, firewood, lumber, and rocks, etc.
  • Inspect and shake out clothing and shoes before getting dressed.
  • Use insect repellants, such as DEET or Picaridin, on clothing and footwear.


  • Clean the bite area with soap and water.
  • Apply ice to the bite area to slow absorption of the venom.
  • Elevate and immobilize the extremity.
  • Capture the spider, if at all possible, for identification purposes.
  • Seek medical attention immediately.
  • If you have a heart condition or other heart problem, you may need hospitalization.

Black Widow Spider

Photo: Extension Entomology, Texas A&M University

Black Widow Spider

Photo: University of Missouri Extension

This is one in a series of informational fact sheets highlighting OSHA programs, policies or standards. It does not impose any new compliance requirements. For a comprehensive list of compliance requirements of OSHA standards or regulations, refer to Title 29 of the Code of Federal Regulations. This information will be made available to sensory impaired individuals upon request. The voice phone is (202) 693-1999; teletypewriter (TTY) number: (877) 889-5627.


For more complete information:

footnote imageOccupational
Safety and Health

U.S. Department of Labor
(800) 321-OSHA


DSG 10/2005

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