SPIDER BITE

 

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Black Widow Spider

  • The black widow is shiny and black, with long legs (total width 1 inch). A red (or orange) hourglass-shaped marking may be on its underside (not present in all Lactrodectus species).

Brown Recluse Spider (Loxosceles reclusa)

  • Characteristic violin-shaped marking is visible on back.

Definition

  • Bite from a spider seen on the skin.
  • Onset of bite symptoms (redness, pain, swelling) and a spider is seen in close proximity

General Information

  • There are over 20,000 species of spiders in the world.
  • In the United States, there are two species that cause bites in humans of medical importance: the black widow (Lactrodectus) and the brown recluse (Loxosceles).
  • If you decide you need to see your doctor, bring the spider along in a jar for identification (brown recluse spiders are especially hard to identify).

Black Widow Spider Bite

  • The black widow is shiny and black, with long legs (total width 1 inch). A red (or orange) hourglass-shaped marking may be on its underside (not present in all Lactrodectus species).
  • Black widow spiders are found throughout North America, except in Alaska and the far North.
  • Causes immediate local mild pain, swelling, and occasionally 2 fang marks. Severe muscle cramps are present by 1 to 6 hours, and last 24 to 48 hours. Rarely causes death (exception: bitten by several spiders or small child is bitten).
  • Note: many are dry bites because the fangs are small.
  • First Aid for Black Widow Spider Bites: Apply an ice cube or ice pack to the bite for 20 minutes to reduce the spread of the venom (no tourniquet).

Brown Recluse Spider Bite

  • Also known as the "violin" or "fiddleback" spider
  • Is a brown spider with long legs (total width 1/2 inch). There is a dark violin-shaped marking on top of its head (not present in all Loxosceles species).
  • It can be found in the southern, southwestern, and midwestern United States.
  • Causes local pain and delayed blister formation in 4 to 8 hours. The center of the bite becomes bluish and depressed (crater-like) over 2 to 3 days. A deep necrotic ulcer may develop. Skin damage may require skin grafting in 10% of cases
  • Generalized symptoms such as fever, vomiting, and muscle aches can occur (but no life-threatening symptoms).

Non-Dangerous Spider Bites

  • More than 50 spiders in the U.S. have venom and can cause local, non-serious reactions.
  • The bites are painful and mildly swollen for 1 or 2 days (much like a bee sting).
  • Most single, unexplained, tender bites that occur during the night are due to spiders.

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Disclaimer: This information is not intended be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.

Adult SelfCareNavigator. Copyright © 2000-2004 David Thompson, M.D. FACEP

Reviewed 8/2004

Revised 7/2002

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