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NIOSH Safety and Health Topic:

Venomous Spiders

Hobo spider Brown recluse Black Widow
Photos courtesy of University of Missouri (hobo spiker), Ohio State University (brown recluse), and Washington State University (black widow)


Venomous spiders found in the United States include the black widow, brown recluse, and hobo spiders. They can be dangerous to outdoor workers including farmers, foresters, landscapers, groundskeepers, gardeners, painters, roofers, pavers, construction workers, laborers, mechanics, and any other worker who spends time outside. These spiders occasionally find their way inside structures or buildings and can also present a risk to indoor workers including machine operators, janitors, and cashiers (Bureau of Labor Statistics Monthly Review - Insects bites, stings cause thousands of workplace injuries). Spiders are usually not aggressive and most bites occur because a spider is trapped or unintentionally contacted. It is important for employers to educate their workers about their risk of exposure to venomous spiders, how they can prevent and protect themselves from spider bites, and what they should do if they are bitten.

Types of Venomous Spiders

Black Widows | Brown Recluse Spiders | Hobo Spiders

Black Widows

Photos courtesy of Ohio State University and University of Missouri

Black widow spiders are found throughout North America, but are most common in the southern and western areas of the United States. They are identified by the pattern of red coloration on the underside of their abdomen. They are usually found in workplaces containing undisturbed areas such as woodpiles, under eaves, fences, and other areas where debris has accumulated. They may also be found living in outdoor toilets where flies are plentiful.

Black widow spiders build webs between objects, and bites usually occur when humans come into direct contact with these webs. A bite from a black widow can be distinguished from other insect bites by the two puncture marks it makes in the skin. The venom is a neurotoxin that produces pain at the bite area and then spreads to the chest, abdomen, or the entire body.

Brown Recluse Spiders

Photos courtesy of Ohio State University and Texas A&M

The brown recluse spider, also known as the violin spider, is most commonly found in the Midwestern and southern states of the United States. It is brown in color with a characteristic dark violin-shaped (or fiddle-shaped) marking on its head and has six equal-sized eyes (most spiders have eight eyes). Brown recluse spiders are usually found in workplaces with secluded, dry, sheltered areas such as underneath structures logs, or in piles of rocks or leaves. If a brown recluse spider wanders indoors, they may be found in dark closets, shoes, or attics.

The brown recluse spider cannot bite humans without some form of counter pressure, for example, through unintentional contact that traps the spider against the skin. Bites may cause a stinging sensation with localized pain. A small white blister usually develops at the site of the bite. The venom of a brown recluse can cause a severe lesion by destroying skin tissue (skin necrosis). This skin lesion will require professional medical attention.

Hobo Spiders

Photos courtesy of Washington State University

The hobo spider is found throughout the Pacific Northwest. It is large and brown with a distinct pattern of yellow markings on its abdomen. Unlike many other similar looking spiders, hobo spiders do not have dark bands on their legs. To catch their prey, hobo spiders build funnel webs in holes, cracks, and recesses. They may be found in outdoor workplaces with retaining walls, and in foundations, window wells, and stacks of firewood and bricks. Indoors, they can nest between boxes or other storage items, on window sills, under baseboard heaters or radiators, behind furniture, and in closets. Hobo spiders do not climb like most spiders but are fast runners. These spiders are much more likely to attack if provoked or threatened. The bite of a hobo spider may go unnoticed; however a moderate to severe, slow-healing wound will develop.


Symptoms associated with spider bites can vary from minor to severe. Although extremely rare, death can occur in the most severe cases. Possible symptoms resulting from a spider bite include the following:

  • Itching or rash
  • Pain radiating from the site of the bite
  • Muscle pain or cramping
  • Reddish to purplish color or blister
  • Increased sweating
  • Difficulty breathing
  • Headache
  • Nausea and vomiting
  • Fever
  • Chills
  • Anxiety or restlessness
  • High blood pressure

Recommendations for Protecting Workers

Employers should protect their workers from spider bites by training them on:

  • Their risk of exposure to spiders
  • How to identify spiders
  • How to prevent exposure to spiders
  • What they should do if they are bitten by a spider


Workers can take the following preventive steps:

  • Inspect or shake out any clothing, shoes, towels, or equipment before use.
  • Wear protective clothing such as a long-sleeved shirt and long pants, hat, gloves, and boots when handling stacked or undisturbed piles of materials.
  • Minimize the empty spaces between stacked materials.
  • Remove and reduce debris and rubble from around the outdoor work areas.
  • Trim or eliminate tall grasses from around outdoor work areas.
  • Store apparel and outdoor equipment in tightly closed plastic bags.
  • Keep your tetanus boosters up-to-date (every 10 years). Spider bites can become infected with tetanus spores.

First Aid

Workers should take the following steps if they are bitten by a spider:

  • Stay calm. Identify the type of spider if it is possible to do so safely. Identification will aid in medical treatment.
  • Wash the bite area with soap and water.
  • Apply a cloth dampened with cold water or filled with ice to the bite area to reduce swelling.
  • Elevate bite area if possible.
  • Do not attempt to remove venom.
  • Notify your supervisor.
  • Immediately seek professional medical attention.

CDC Resources

CDC - Spiders: Key to Some Important U.S. Species
this document in PDF 504.95 KB (1 page)

CDC/National Agriculture Safety Database - Video for Outdoor Workers: Killer Bees Wasps Spiders

Additional Resources

The National Capital Poison Center
External link:

Occupational Safety and Health Administration (OSHA) – Fact Sheet: Black Widow Spider
this document in PDF 29.89 KB (1 page)

OSHA – Fact Sheet: Brown Recluse Spider
this document in PDF 27.53 KB (1 page)

National Library of Medicine (NLM) – Black Widow Spiders
External link:

NLM Medical Encyclopedia – Brown Recluse Spider
External link:

University of California – Integrated Pest Management Program: Brown Recluse and Other Recluse Spiders
External link:

Ohio State University Extension – Fact Sheet: Black Widow Spider
External link:

Washington State University – How to Identify (or Misidentify) the Hobo Spider
this document in PDF 394.82 KB (10 pages)

Texas A&M University – Texas Cooperative Extension: Spiders
External link:

Page last updated: October 22, 2008
Page last reviewed: October 22, 2008
Content Source: National Institute for Occupational Safety and Health (NIOSH)

Venomous Spiders

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