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Black widow spider

The black widow spider has a shiny black body with a red hourglass-shape on its belly area. The bite of a black widow spider is poisonous.

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.

Poisonous Ingredient

The venom of the black widow spider contains poisonous 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.

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.

  • If the bite is on the upper body, you will usually feel most of the pain in your chest.
  • If the bite is on your lower body, you will usually feel most of the pain in your abdomen.

The following symptoms can also occur:

Pregnant women may have contractions and go into labor.

Home Care

Seek emergency medical treatment right away. Wrap ice in a clean cloth and place it on the bite area. Leave it on for 10 minutes and then off for 10 minutes. Repeat this process. If the person has blood flow problems, decrease the time that the ice is on the area to prevent possible skin damage.

Before Calling Emergency

Have this information ready:

  • Person's age, weight, and condition
  • Time the bite occurred
  • Area on the body where the bite occurred
  • Type of spider, if possible

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:

  • Blood and urine tests
  • Breathing support, including oxygen
  • Chest or abdominal x-rays
  • EKG (electrocardiogram, or heart tracing)
  • Intravenous fluids (through a vein)
  • Medicines to treat symptoms

In severe cases, a type of medicine called antivenin is given to reverse the effect of the poison. However, this drug 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, the very ill, and the elderly may not survive a bite.

To prevent a bite, wear protective clothing when travelling in areas where black widow spiders live. DO NOT stick your hands or feet in their nests or in places where they may be hiding, such as under logs or underbrush, or other damp, moist areas.

References

Boyer LV, Greta J. Binford GJ, et al. Spider bites. In: Auerbach PS, ed. Wilderness Medicine. 6th ed. Philadelphia, PA: Elsevier Mosby; 2011:chap 52.

Gross KR, Collier BR, Riordan WP, Jr., et al. Wilderness Trauma and Surgical Emergencies. In: Auerbach PS, ed. Wilderness Medicine. 6th ed. Philadelphia, PA: Elsevier Mosby; 2011:chap 21.

Otten EJ. Venomous animal injuries. In: Marx JA, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 62.

Review Date 7/14/2015

Updated by: Jacob L. Heller, MD, MHA, Emergency Medicine, Virginia Mason Medical Center, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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