Diagnosis

Your doctor may suspect a spider bite based on your history and your signs and symptoms. The process might involve talking to someone who saw the bite, having an expert identify the spider and ruling out other possible causes of the symptoms.

Black widow identification

Some clues for identifying black widow spiders include:

  • Shiny black body with long legs
  • Red hourglass on underside of abdominal area
  • Entire body, including legs, is about 1 inch (2.5 centimeters) across

Brown recluse identification

Some clues for identifying brown recluse spiders include:

  • Golden or dark brown body with long legs
  • Dark violin shape on top of the leg attachment segment
  • Six eyes — a pair in front and a pair on both sides — rather than the usual spider pattern of eight eyes in two rows of four
  • Central body is 0.25 to 0.75 inches (6 to 19 mm) long

Treatment

Treatment for spider bites usually includes the following steps:

  • Clean the bite with mild soap and water. Apply an antibiotic ointment to help prevent infection.
  • Apply a cool damp cloth to the bite. This helps reduce pain and swelling.
  • If the bite is on an arm or leg, elevate it.
  • Take an over-the-counter pain reliever as needed.
  • Observe the bite for signs of infection.

Your doctor may also recommend a tetanus booster shot if you haven't had one in the last five years. You may need antibiotics if the bite becomes infected.

Black widow antivenom

If a black widow bite is causing severe pain or life-threatening symptoms, your doctor may recommend antivenom, which may be injected into a thigh muscle or given through a vein (intravenously). Antivenom can cause serious allergic reactions, so it must be used with caution.

Preparing for your appointment

If you've been bitten by a spider that you suspect is a black widow or brown recluse, call your primary care doctor or go to an urgent care center. If your doctor has online services, an option may be to email a photo of the spider to your doctor.

What you can do

To help your doctor understand your symptoms and how they might relate to a spider bite, you can:

  • Bring the spider or a photo of the spider with you
  • List any symptoms you're experiencing
  • List questions to ask your doctor

Some basic questions you might want to ask include:

  • If this is a dangerous spider bite, what's the next best step?
  • If this isn't a spider bite, what are possible causes for my symptoms or condition?
  • Do I need any tests?
  • How long will my symptoms last?
  • What is the best course of action?

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

  • When did you begin experiencing symptoms?
  • What were you doing in the hours before your symptoms started?
  • Have your symptoms gotten worse?
  • Does anything relieve your symptoms or make them worse?
May 15, 2019
  1. Vetter RS, et al. Approach to the patient with a suspected spider bite: An overview. https://www.uptodate.com/contents/search. Accessed March 22, 2019.
  2. Habif TP. Infestations and bites. In: Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 6th ed. St. Louis, Mo.: Saunders Elsevier; 2016. https://www.clinicalkey.com. Accessed March 22, 2019.
  3. Thompson, DA. Spider bite. In: Adult Telephone Protocols: Office Version. 4th ed. Itasca, IL: American Academy of Pediatrics; 2018.
  4. Venomous spiders. National Institute for Occupational Safety and Health. https://www.cdc.gov/niosh/topics/spiders. Accessed March 22, 2019.
  5. Vetter RS, et al. Management of widow spider bites. https://www.uptodate.com/contents/search. Accessed March 22, 2019.
  6. Vetter RS, et al. Bites of recluse spiders. https://www.uptodate.com/contents/search. Accessed March 22, 2019.
  7. Brown recluse spider. Occupational Safety and Health Administration. https://www.osha.gov/OshDoc/data_Hurricane_Facts/brown_recluse_spider.html. Accessed March 22, 2019.
  8. Diaz JH, et al. Common spider bites. American Family Physician. 2007;75:869.