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Black widow spider

The black widow spider (Latrodectus genus) has a shiny black body with a red hourglass-shape on its belly area. The venomous bite of a black widow spider is toxic. The genus of spiders, to which the black widow belongs, contains the largest number of venomous species known.

This article is for information only. DO NOT use it to treat or manage a black widow spider bite. If you or someone you are with is bitten, call your local emergency number (such as 911), or your local poison center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States.

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Arthropods - basic features
Arachnids - basic features
Black widow spider

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Poisonous Ingredient

The venom of the black widow spider contains toxic chemicals that make people sick.

Where Found

Black widows are found throughout the United States, mostly in the South and West. They are usually found in barns, sheds, stone walls, fences, woodpiles, porch furniture, and other outdoor structures.

This genus of spider species is found worldwide. They are most plentiful in temperate and subtropical climates, especially during the summer months.

Symptoms

The first symptom of a black widow bite is usually pain similar to a pinprick. This is felt when the bite is made. Some people may not feel it. Minor swelling, redness, and a target-shaped sore may appear.

After 15 minutes to 1 hour, a dull muscle pain spreads from the bite area to the whole body.

The following symptoms can also occur:

Pregnant women may have contractions and go into labor.

Home Care

Black widow spider bites are very toxic. Seek medical help right away. Call the Poison Control Center for guidance.

Follow these steps until medical help is given:

Before Calling Emergency

Have this information ready:

Poison Control

Your local poison center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States. They will give you further instructions.

This is a free and confidential service. All local poison control centers in the United States use this national number. You should call if you have any questions about poisoning or poison prevention. It does NOT need to be an emergency. You can call for any reason, 24 hours a day, 7 days a week.

What to Expect at the Emergency Room

If possible, bring the spider to the emergency room. Put it in a secure container.

The health care provider will measure and monitor the person's vital signs, including temperature, pulse, breathing rate, and blood pressure. The person may receive:

In general, children, pregnant women, and older people may need to be given Latrodectus antivenom to reverse the effect of the venom. However, it can cause serious allergic reactions and must be used carefully.

Outlook (Prognosis)

Severe symptoms usually start to improve within 2 to 3 days, but milder symptoms may last for several weeks. Death in a healthy person is very rare. Young children, people who are very ill, and older people may not survive a bite.

Wear protective clothing when traveling through areas where these spiders live. DO NOT put your hands or feet in their nests or in their preferred hiding places, such as dark, sheltered areas under logs or underbrush, or other damp, moist areas.

References

Boyer LV, Binford GJ, Degan JA. Spider bites. In: Auerbach PS, Cushing TA, Harris NS, eds. Auerbach's Wilderness Medicine. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 43.

James WD, Elston DM, Treat JR, Rosenbach MA, Neuhaus IM. Parasitic infestations, stings, and bites. In: James WD, Elston DM, Treat JR, Rosenbach MA, Neuhaus IM, eds. Andrews' Diseases of the Skin: Clinical Dermatology. 13th ed. Philadelphia, PA: Elsevier; 2020:chap 20

Otten EJ. Venomous animal injuries. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 55.

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Review Date: 6/30/2019  

Reviewed By: Jacob L. Heller, MD, MHA, Emergency Medicine, Emeritus, Virginia Mason Medical Center, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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