Brown Recluse Spider Bite

Elsevier Patient Education © 2023 Elsevier Inc..
Last revised: October 6, 2023.

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Brown recluse spiders (Loxosceles species) are found mainly in the southeastern part of the United States, as far north as Illinois. In the United States, bites usually occur in warmer months (April through October). When a brown recluse spider bites, it can inject poison (venom) into the wound. In most cases, a bite from a brown recluse spider causes mild redness and swelling around the bite. In rare cases, a bite can be serious and even life-threatening. If you think you were bitten by a brown recluse spider, get medical help right away.

Brown recluse spiders can be dark brown to light tan in color. On their back, they have a band of darker color that is shaped like a violin. They may be found outdoors underneath items that are lying on the ground. They may also live indoors in places that are out of the way, such as attics.

What are the causes?

A spider bite is often caused by a person accidentally making contact with a spider in a way that traps the spider against the skin.

What are the signs or symptoms?

Symptoms of this condition may include:

  • Pain and redness around the bite. At first, the bite may be a small, painful blister with redness around it. The blister may break open and create a sore (ulcer) that can get worse and spread over time. A severe ulcer may cause up to 12 inches (30 cm) of tissue around the bite to die.

  • A general feeling of sickness (malaise).

  • Nausea or vomiting.

  • Fever.

  • Body aches.

Symptoms may start to get worse several days after you are bitten.

In rare cases, the bite can cause more serious symptoms. This is most likely to happen in children, or if you are bitten by a South American species of the spider. Serious symptoms usually develop during the first 48–72 hours after the bite. They may include:

  • Skin or the white parts of your eyes turn yellow (jaundice).

  • Breakdown of red blood cells (hemolytic anemia).

  • Dark or bloody urine or decreased urination. These could be signs of kidney failure.

How is this diagnosed?

This condition may be diagnosed based on:

  • Your symptoms.

  • A physical exam.

  • Any details you have about how the bite happened and what the spider looked like.

How is this treated?

There is no single cure (antidote) to treat this bite. A bite wound may take 1–2 months to heal. Treatment is focused on wound care, and may involve:

  • Covering the wound with a bandage (dressing).

  • Medicines to treat the ulcer and help prevent tissue death.

  • Antibiotic medicine. This may be taken by mouth or applied to the bite area.

  • Tetanus shot.

Treatment for more serious cases may include:

  • Receiving donated red blood cells (transfusion), for hemolytic anemia.

  • Surgery to remove damaged tissue. This may be needed if a large ulcer develops.

  • IV fluids for kidney failure.

  • Dialysis, for severe kidney failure. Dialysis is a treatment that filters the blood when the kidneys cannot.

Follow these instructions at home:

Medicines

  • Take or apply over-the-counter and prescription medicines only as told by your health care provider.

  • If you were prescribed an antibiotic medicine, take or apply it as told by your health care provider. Do not stop using the antibiotic even if you start to feel better or if your condition improves.

Wound care

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  • Follow instructions from your health care provider about how to take care of your bite wound. Make sure you:

    • Wash your hands with soap and water for at least 20 seconds before and after you change your dressing. If soap and water are not available, use hand sanitizer.

    • Change your dressing as told by your health care provider.

    • Keep the bite area clean and dry.

    • Wash the bite area daily with soap and water, as told by your health care provider.

  • Do not scratch the bite area.

  • Check the bite area every day for signs of infection. Check for:

    • More redness, swelling, or pain.

    • Fluid or blood.

    • Warmth.

    • Pus or a bad smell.

General instructions

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  • If directed, put ice on the bite area. To do this:

    • Put ice in a plastic bag.

    • Place a towel between your skin and the bag.

    • Leave the ice on for 20 minutes, 2–3 times a day.

    • Remove the ice if your skin turns bright red. This is very important. If you cannot feel pain, heat, or cold, you have a greater risk of damage to the area.

  • Raise (elevate) the bite area above the level of your heart while you are sitting or lying down.

  • Keep all follow-up visits. This is important.

Contact a health care provider if you:

  • Notice that your symptoms get worse or do not improve after 24 hours.

  • Have more redness, swelling, or pain around your wound.

  • Notice that your wound feels warm to the touch.

  • Feel malaise.

Get help right away if you:

  • Notice that your wound:

    • Seems to be getting larger or growing deeper.

    • Has pus or a bad smell coming from it.

    • Has fluid or blood coming from it.

  • Have chills or a fever.

  • Have muscle aches.

  • Have involuntary muscle movements (convulsions).

  • Develop a rash.

  • Urinate less often than usual.

  • Have blood in your urine or other unusual bleeding.

  • Notice that your skin or the white parts of your eyes turn yellow.

These symptoms may represent a serious problem that is an emergency. Do not wait to see if the symptoms will go away. Get medical help right away. Call your local emergency services (911 in the U.S.). Do not drive yourself to the hospital.

Summary

  • Brown recluse spider bites usually occur in warmer months (April through October).

  • Brown recluse spiders can be dark brown to light tan in color and have a dark brown violin shape on their back.

  • In most cases, a bite from a brown recluse spider causes mild redness and swelling around the bite. In rare cases, more serious issues can occur, like yellowing of the skin, anemia, or kidney failure.

  • There is no single cure to treat this bite. Treatment is focused on wound care.

  • A bite wound may take 1–2 months to heal.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.