What Are Black Widow and Brown Recluse Spiders?
- Black widow spiders (Latrodectus mactans) may be black or brown with a leg span of approximately one to two inches. Most can be identified by a red hourglass marking on the abdomen.
- Black widow spiders are located throughout the United States.
- Black widow toxin causes nerve cell dysfunction and muscle cell twitching.
- Brown recluse spiders (Loxosceles reclusa) are tan to dark brown with a leg span of approximately 1 inch. Many have a violin-shaped marking on the chest.
- Brown recluse spiders are located mainly in the south central United States.
- Both black widow and brown recluse spiders are common in North America and throughout the world. Human contact with these spiders is usually accidental.
Spider Bite Symptoms
Black widow a spider bites result in a halo lesion consisting of a pale circular area surrounded by a ring of redness.
- The initial bite of the black widow spider is usually painful, and the victim will often note the spider during the bite.
- Numbness, tingling, rashes, sweating, nausea, vomiting, dizziness, cramps, rigid abdominal muscles, chest tightness, weakness, and difficulty breathing may occur.
- The abdominal pain due to the spider bite can be so severe that it mimics abdominal medical conditions such as pancreatitis.
- Hypertension (high blood pressure) is a possible reaction to the venom.
Brown recluse bites are tender, red, swollen, and form blisters. The initial bite may or may not be noticed by the victim.
- Brown recluse bites cause local swelling, pain, itching, redness, tenderness, and blisters. They eventually form large ulcers and may cause tissue necrosis (death of the tissue in the area of the bite).
- Fever, chills, rash, nausea, and vomiting may develop.
- More severe reactions include kidney failure, blood coagulation abnormalities, and difficulty breathing. Death can occur. Symptoms of allergic reaction may be present.
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Spider Bite Treatment
- Wash the bite with soap and water and remove all jewelry. Swelling can occur and will make it difficult to remove some jewelry.
- Apply cool compresses.
- Take diphenhydramine (Benadryl) 25- to 50-mg tablets every six hours for the itch.
- Take acetaminophen (Tylenol), one to two tablets every four hours, for pain. Avoid aspirin, ibuprofen (Motrin, Advil), and naproxen (Aleve). The pain resulting from a black widow spider bite is usually so severe that it will require strong pain medications such as opioids.
- Antibiotics are not helpful unless secondary infection develops.
- Do not cut into the wound or apply suction.
- See a doctor as soon as possible.
When to Seek Medical Care
- Seek immediate medical care.
- Antivenom therapy is available for black widow bites. Medications, if started early, are available to treat brown recluse bites. However, the efficacy of the medications for the treatment of brown recluse spider bites is controversial.
- Consult a doctor about treatment with available medications.
Medically reviewed by Robert L. Cox, MD; Board Certification Internal Medicine/Infectious Disease
"Clinical manifestations and diagnosis of widow spider bites"
"Bites of recluse spiders"