SPIDER BITE

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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WHEN TO CALL YOUR DOCTOR FOR SPIDER BITE

Call 911 Now (you may need an ambulance) If:

  • Difficulty breathing or swallowing
  • Very weak (can't stand)

Call Your Doctor Now (night or day) If:

  • You feel weak or very sick

  • Any black widow spider bite
  • Abdominal pain, chest tightness or other muscle cramps
  • Vomiting
  • Urine is brown, black or red in color
  • Bite pain is severe
  • Bite looks infected (red streaking from the bite area, yellow drainage)  (Note: infection doesn't start until at least 24-48 hours after the bite.  Any redness in the first 24 hours is due to venom)

Call Your Doctor Within 24 Hours (between 9am and 4pm) If:

  • You think you need to be seen
  • Diabetic and spider bite of foot
  • Bite starts to look bad (e.g. skin damage, blister or purplish - not just swelling)
  • Bite pain persists longer than 2 days

Call Your Doctor During Weekday Office Hours If:

  • You have other questions or concerns

Self Care at Home If:

  • Non-serious spider bite and you don't think you need to be seen
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HOME CARE ADVICE FOR NON-SERIOUS SPIDER BITE

  1. Cleansing: Wash the bite thoroughly with soap and water.
  2. Meat Tenderizer: Rub the bite area with a cotton ball soaked in a meat tenderizer solution for 20 minutes.  (Exception: don't use near the eye.)  If not available, apply an ice cube for 20 minutes.
  3. Pain Medication: For pain relief, take acetaminophen every 4-6 hours (e.g. Tylenol; adult dosage 650 mg) OR ibuprofen every 6-8 hours (e.g. Advil, Motrin; adult dosage 400 mg).
    • Do not take ibuprofen if you have stomach problems, kidney disease, are pregnant, or have been told by your doctor to avoid this type of anti-inflammatory drug. Do not take ibuprofen for more than 7 days without consulting your doctor.
    • Do not take acetaminophen if you have liver disease.
    • Read the package instructions thoroughly on all medications that you take.
  4. Expected Course: Some swelling and pain for 1 to 2 days. It shouldn't be any worse than a bee sting.
  5. Call Your Doctor If:
    • Severe bite pain persists longer than 2 hours after pain medicine
    • Abdominal pains or muscle spasms occur
    • Local pain lasts more than 2 days (48 hours)
    • Bite begins to look infected
    • You become worse or develop any of the "Call Your Doctor" symptoms.
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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 HouseCalls Online. Copyright © 2000-2003 David Thompson, M.D. FACEP

Reviewed 8/2003

Revised 7/2002

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