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Black widow spider
URL of this page: //medlineplus.gov/ency/article/002858.htm


BLACK WIDOW SPIDER


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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 the local
emergency number (such as 911), or the local poison control 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

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The venom of the black widow spider contains toxic chemicals, including the
neurotoxin alpha latrotoxin, that make people sick.


WHERE FOUND

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Black widow spiders 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. They are usually, but
not always, found near ground level, or within a few feet of the ground. They
make irregular, asymmetrical, "disorganized" looking webs.

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

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.


SYMPTOMS

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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:

 * Anxiety
 * Difficulty breathing
 * Headache
 * High blood pressure
 * Increased saliva
 * Increased sweating
 * Light sensitivity
 * Muscle weakness
 * Nausea and vomiting
 * Numbness and tingling around the bite site, then sometimes spreading out from
   the bite
 * Restlessness
 * Seizures (usually seen just before death in children who are bitten)
 * Very painful muscle cramps or spasms
 * Facial swelling in the hours after the bite (This pattern of swelling is
   sometimes confused with an allergy to the drug used in treatment.)

Pregnant women may have contractions and go into labor.


HOME CARE

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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:

 * Clean the area with soap and water.
 * 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.
 * Keep the affected area still, if possible, to prevent the venom from
   spreading. A homemade splint may be helpful if the bite was on the arms,
   legs, hands, or feet.
 * Loosen clothing and remove rings and other tight jewelry.


BEFORE CALLING EMERGENCY

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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

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Your local poison control center can be reached directly by calling the national
toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United
States. This national hotline will let you talk to experts in poisoning. 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

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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:

 * Antivenin, a medicine to reverse the effects of the venom, if available
 * Blood and urine tests
 * Breathing support, including oxygen, tube through the mouth into the throat,
   and breathing machine (ventilator)
 * Chest x-rays, abdominal x-rays, or both
 * ECG (electrocardiogram, or heart tracing)
 * Intravenous fluids (IV, or through a vein)
 * Medicines to treat symptoms

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


OUTLOOK (PROGNOSIS)

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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.


IMAGES

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 * Arthropods - basic features
 * Arachnids - basic features
 * 
 * Black widow spider


REFERENCES

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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.

Curtis AM, Erickson TB. Venomous animal injuries. In: Walls RM, ed. Rosen's
Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA:
Elsevier; 2023:chap 53.

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.

Liao L, Norris RL, Nelson EE, Stewart RM. Bites and stings. In: Townsend CM Jr,
Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 21st ed.
St Louis, MO: Elsevier; 2022:chap 21.


REVIEW DATE 7/1/2023

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Updated by: Jesse Borke, MD, CPE, FAAEM, FACEP, Attending Physician at Kaiser
Permanente, Orange County, CA. Also reviewed by David C. Dugdale, MD, Medical
Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

Learn how to cite this page



RELATED MEDLINEPLUS HEALTH TOPICS

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 * Spider Bites


RELATED MEDLINEPLUS HEALTH TOPICS

 * Spider Bites


IMAGES

 * Arthropods - basic features
 * Arachnids - basic features
 * 
 * Black widow spider


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