Community Health Network

• 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).
• Sometimes people incorrectly believe that they sustained a spider bite, when instead a minor break in the skin instead simply became infected with a bacteria called Staphylococcus aureus.

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.