Black Widow Spider Bite

Elsevier Patient Education © 2023 Elsevier Inc..
Last revised: September 27, 2023.

Black widow spiders can inject poison (venom) into the wound when they bite a person. In some cases, these bites can be serious and even life-threatening. If you think that you were bitten by a black widow spider, you should get medical help right away.

Black widow spiders have a black body with an orange–red hourglass shape on their abdomen. They may be found outdoors under items that are lying on the ground, in woodpiles, or in outdoor structures, such as sheds or garages. If they are indoors, they are usually found in dark, cluttered areas.

What are the causes?

A spider bite is usually 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?

How is this diagnosed?

How is this treated?

If you have a severe reaction, you may need to be treated at a hospital. You may be given an injection of medicine to counteract the venom (antivenom). This is done only for very severe reactions that are not effectively treated with other medicines.

Follow these instructions at home:

Wound care

• 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

• 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:

• Have muscle cramps.

• Have pain or cramps in your abdomen.

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

• Have warm skin around your wound.

• Develop weakness or numbness in part of your body.

• Feel generally sick (malaise).

Get help right away if you:

• Develop rapid breathing or a rapid heartbeat.

• Become very restless or confused.

• Have chest pain.

• Feel light-headed.

• Have fluid or blood coming from your wound.

• Have pus or a bad smell coming from your wound.

• Have a fever.

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

• Black widow spiders have a black body with an orange–red hourglass shape on their abdomen.

• Black widow spiders can inject poison (venom) into the wound when they bite a person. In some cases, these bites can be life-threatening. If you think that you were bitten by a black widow spider, you should get medical help right away.

• Symptoms usually develop an hour after the bite. Symptoms can range from mild to severe.

• Treatment includes covering the bite, taking medicine, and getting a tetanus shot. If you have a severe reaction, you may need to take medicine to counteract the venom (antivenom).

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.