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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).

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

Black Widow Spider Bite

• Description: A shiny, jet-black spider with long legs (total size 1 inch). A red (or orange) hourglass-shaped marking may be on its under-side (not present in all Lactrodectus species).

• Habitat: Found throughout North America, except Alaska and the far North.

• Symptoms - Bite Wound: The black widow spider produces one of nature's most potent neurotoxic venoms. The bite causes immediate moderate to severe pain; there is usually minimal to no local reaction.

• Symptoms - Systemic: Severe muscle cramps are present by 1 to 6 hours, and last 24 to 48 hours. Other possible symptoms include abdominal pain, vomiting, restlessness, hypertension, and weakness.

• Treatment - Local Wound Care: Wash bite with soap and water. Apply an ice pack.

• Treatment - Medications: Tetanus prophylaxis should be provided. Parenteral analgesics may be needed for pain and benzodiazepines for muscle spasms. There is a Lactrodectus antivenin that is indicated for severe symptoms, seizures, or uncontrolled hypertension.

• Expected Course: All symptoms usually resolve over 2-3 days. Death may occur rarely; a bite is more serious in a small child; multiple spider bites are also more serious.

• Special Note: Many bite wounds are "dry bites" (no venom injected into skin) because the fangs are small.

Brown Recluse Spider Bite

• Also known as the "violin" or "fiddleback" spider.

• Description: A brown spider with long legs (total size 1/2 inch). dark violin-shaped marking on top of its head (not present in all Loxosceles species).

• Habitat: Found in the southern, southwestern and midwestern United States.

• Symptoms - Bite Wound: The spider produces a venom which causes cell destruction and blood cell breakdown. The bite is initially painless or minimally painful. Local pain and blister formation develops in 4 to 8 hours. The center becomes bluish and depressed (crater-like) over 2 to 3 days. A deep necrotic ulcer may develop.

• Symptoms - Systemic: Systemic symptoms include fever, vomiting, and myalgias (but no life-threatening symptoms).

• Treatment - Local Wound Care: Cleansing of wound with soap and water, cold pack.

• Treatment - Medications: Tetanus prophylaxis should be provided.

• Expected Course: Most necrotic ulcers heal over one to eight weeks. Permanent scarring occurs in 10-15 percent. Skin damage sometimes requires skin grafting.

Tarantulas

• Habitat: Tarantulas are found in the southern United States (e.g., Desert Southwest).

• Symptoms - Bite Wound: Mild stinging with minimal local inflammation. No skin necrosis occurs.

• Symptoms - Eye: Some genera of tarantula have "urticating" hairs that can come off. Like a little piece of fiberglass, they can penetrate human skin and cause itching and redness. If they lodge in the cornea they can cause foreign body keratoconjunctivitis or ophthalmia nodosa.

• Symptoms - Systemic: None.

• Treatment - Local Wound Care: Cleansing of bite wound with soap and water, cold pack, oral analgesics. Obtaining a tetanus booster is appropriate if it has been longer than 10 years.

• Treatment - Eye Irritation: Individuals with eye irritation or redness after handling a tarantula should be referred to an ophthalmologist for a slit lamp examination of the eye,

• Expected Course: Bite wounds heal completely. Eye problems generally resolve under the close follow-up care of an ophthalmologist.

Minor (Non-Dangerous) Spider Bites

• More than 50 spiders in the U.S. and Canada have venom and can cause minor, localized, non-serious reactions. Many single, unseen and unexplained painful bites that occur during the night can be due to spiders.

• Symptoms - Bite Wound: The bites are painful and mildly swollen for 1 or 2 days (much like a bee sting).

• Symptoms - Systemic: None.

• Treatment - Local Wound Care: Cleansing of bite wound with soap and water, cold pack, oral analgesics. Obtaining a tetanus booster is appropriate if it has been longer than 10 years.

• Expected Course: Bite wounds heal completely.

If not, see these topics

• TICK BITES

• BEE STING

• Bite and not from a tick or spider, see INSECT BITES

When to Call Your Doctor

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 (or brown widow) spider bite

• Abdominal pain, chest tightness or other muscle cramps

• Vomiting

• Urine is brown, black or red in color

• Severe bite pain and not improved after 2 hours of pain medicine

• Redness, red streak, or very tender area (to touch), and you also have a fever

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

• You think you need to be seen

• Red or very tender (to touch) area, and started over 24 hours after the bite

• Red or very tender (to touch) area, getting larger over 48 hours after the bite

• Diabetic and spider bite of foot

• Bite starts to look bad (e.g., blister, purplish skin, ulcer)

• Eye irritation after handling or touching a tarantula

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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