Health Encyclopedia

Brown recluse spider

Definition

Brown recluse spiders are between 1 and 1 1/2 inches (2.5 to 3.5 centimeters) long. They have a dark brown, violin-shaped mark on their upper body and light brown legs. Their lower body may be dark brown, tan, yellow, or greenish. They also have 3 pairs of eyes, instead of the usual 4 pairs other spiders have. The bite of a brown recluse spider is venomous.

This article is for information only. DO NOT use it to treat or manage a brown recluse 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.

Alternative Names

Loxosceles reclusa

Poisonous Ingredient

The venom of the brown recluse spider contains toxic chemicals that make people sick.

Where Found

The brown recluse spider is most common in the south and central states of the United States, especially in Missouri, Kansas, Arkansas, Louisiana, eastern Texas, and Oklahoma. However, they have been found in several large cities outside these areas.

The brown recluse spider prefers dark, sheltered areas, such as under porches and in woodpiles.

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

When the spider bites you, you may feel a sharp sting or nothing at all. Pain usually develops within the first several hours after being bitten, and may become severe. Children may have more serious reactions.

Symptoms may include:

• Chills
• Itching
• General ill-feeling or discomfort
• Fever
• Nausea
• Reddish or purplish color in a circle around bite
• Sweating
• Large sore (ulcer) in the area of the bite

Rarely, these symptoms may occur:

• Coma (lack of responsiveness)
• Blood in urine
• Yellowing of the skin and whites of the eyes (jaundice)
• Kidney failure
• Seizures

In serious cases, blood supply is cut off from the area of the bite. This results in black tissue scarring (eschar) at the site. The eschar sloughs off after about 2 to 5 weeks, leaving an ulcer through skin and fatty tissue. The ulcer may take many months to heal and leave a deep scar.

Home Care

Seek emergency medical treatment right away. Call 911 or the local emergency number, or poison control.

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

Have this information ready:

• Person's age, weight, and condition
• The body part affected
• The time the bite occurred
• The type of spider, if known

Take the person to the emergency room for treatment. The bite may not look serious, but it can take some time to become severe. Treatment is important to reduce complications. If possible, place the spider in a secure container and bring it to the emergency room for identification.

Poison Control

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

Take the spider to the emergency room with you, if possible. Make sure it is 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.

Symptoms will be treated. Because brown recluse spider bites can be painful, pain medicines may be given. Antibiotics may also be prescribed if the wound is infected.

If the wound is near a joint (such as a knee or elbow), the arm or leg may be placed into a brace or sling. If practical, elevate the arm or leg.

In more serious reactions, the person may receive:

• Blood and urine tests
• Breathing support, including oxygen, tube through the mouth into the throat, and breathing machine (ventilator)
• Chest x-ray
• ECG (electrocardiogram, or heart tracing)
• Intravenous fluids (IV, or through a vein)
• Medicines to treat symptoms

Outlook (Prognosis)

With proper medical attention, survival past 48 hours is usually a sign that recovery will follow. Even with appropriate and quick treatment, symptoms may last for several days to weeks. The original bite, which may be small, may progress to a blood blister and look like a bull's eye. It may then become deeper, and additional symptoms such as fever, chills, and other signs of additional organ system involvement may develop. If scarring from an ulcer has developed, surgery may be needed to improve the appearance of the scar formed at the site of the bite.

Death from brown recluse spider bites is more common in children than adults.

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.

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
Reviewed 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.

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