Spider Bites

Overview

How serious is a spider bite?

Most spiders are harmless and rarely bite people. All spiders make venom (a poison), but most spiders’ fangs are too small to puncture human skin.

Spiders are arachnids (not insects). They’re in the same class as scorpions, mites and ticks. All of these arachnids have eight legs. Spiders perform a vital function by eating insects that can destroy crops.

Which spiders are dangerous to people?

There are at least 60 different spider species in America, but only a few pose any danger to humans. These more dangerous spiders include:

  • Black widows: These black spiders have a red hourglass shape on their bellies. Black widows like to build webs in woodpiles, building overhangs (eaves), fences and outhouses. They mostly live in the Western and Southern U.S.

bwspider

Black widow spider

  • Brown recluses: Sometimes called fiddleback or violin spiders, these brown spiders have a dark, violin-shaped mark on their heads. Brown recluses live in Midwestern and Southern states. They like dry, sheltered areas, such as piles of wood, rocks and leaves. Indoors, brown recluses seek out dark closets, attics and shoes.

brnreclusespider

Brown recluse spider

  • Hobo spiders: These brown spiders have a grey V-shaped (herringbone) pattern on their bellies. They build funnel-shaped webs in dark, moist basements, crawl spaces, window wells and woodpiles. Hobo spiders are mostly found in the Pacific Northwest.

hobospiders

Hobo spider

How common are spider bites?

Experts aren’t sure how many people get spider bites every year. Most of the time, you may not know a spider bit you. Or you may think an insect bit you, instead of a spider.

Bites from black widows or brown recluses are most dangerous to children (because of their small size) and the elderly (who may be frail or in poor health). In the U.S., fewer than three people die every year from a spider bite. Most of these deaths occur in children.

Who might get spider bites?

Anyone can accidentally come into contact with a spider and get bitten. Still, some people may be more at risk because their jobs or actions put them in closer contact with places where spiders live. People at risk include:

  • Outdoor workers, including landscapers, groundskeepers and farmworkers.
  • Children who play in piles of leaves or rocks.
  • Hikers.
  • Janitors.
  • Machine operators.

Symptoms and Causes

What are the symptoms of a spider bite?

Spider bite symptoms vary depending on the type of spider.

Black widow spider bites cause an immediate, sharp, pinprick-like pain. The bite area then becomes numb. Other signs of a black widow spider bite include:

Bites from brown recluse spiders aren’t immediately painful or noticeable. Instead, you might feel pain an hour after the bite. Other signs of a brown recluse spider bite include:

  • A blister surrounded by a bruise or reddish skin color (similar to a bull’s-eye). The blister may rupture and form a skin ulcer that later scars.
  • Itchy skin in the bite area or all over the body.

Hobo spider bites rarely cause pain. Signs of a hobo spider bite include:

  • Severe headache within minutes or hours after the bite. This headache may last for a week.
  • Hardened skin in the bite area within 30 minutes of the bite.
  • Red, swollen skin.
  • Blisters that produce pus.
  • Fatigue.
  • Nausea.
  • Cognitive impairment (memory problems).

Diagnosis and Tests

How is a spider bite diagnosed?

Seeing the spider is the best way to confirm both a bite and the type of spider. Otherwise, there isn’t a way to test for a spider bite or determine what bit you.

Your healthcare provider may make a diagnosis based on symptoms. Your provider may also send a sample of fluid from a blister to a lab to check for skin infections that cause similar symptoms, such as methicillin-resistant staphylococcus aureus (MRSA).

Management and Treatment

What are the complications of a spider bite?

Some brown recluse bites cause a skin ulcer (wound). If the wound doesn’t heal, you might need surgery.

Black widow bites are the most serious. Children under 16 and people older than 60 may need hospitalization to treat:

How is a spider bite managed or treated?

Spider bite treatments vary depending on symptoms. Treatment for black widow spider bites includes muscle relaxers, sedatives and pain medicines.

Treatment for brown recluse and hobo spider bites include:

  • Daily cleaning with a povidone-iodine solution to prevent infection.
  • Soaking the bite area in sterile saltwater (saline) solution three times a day.

What should I do if a spider bites me?

You should never attempt to suck out or remove venom from a spider bite. Instead, follow these steps:

  1. Clean the bite area with warm water and soap.
  2. Apply a cold, damp washcloth or an ice pack to the bite area.
  3. Elevate the bite area.
  4. Take an antihistamine (allergy medicine) to ease itching and swelling.
  5. Take an over-the-counter pain reliever for pain and swelling.
  6. Seek immediate medical attention for severe symptoms.

Prevention

How can I protect myself from spider bites?

To protect yourself and your family from spider bites:

  • Apply insect repellant that’s registered with the Environmental Protection Agency (EPA).
  • Keep firewood outside and check it for spiders before bringing it into the house.
  • Shake your shoes, hats and gloves to check for spiders before putting them on.
  • Treat clothing and shoes with permethrin, an insecticide.
  • Wear gloves when carrying wood, working in the garden, moving rocks or in other outdoor settings.
  • Wear long sleeves and pants in wooded areas.

Outlook / Prognosis

What is the prognosis (outlook) for people who have spider bites?

Most people with spider bites experience mild symptoms like pain and swelling. These symptoms gradually go away with at-home care.

You may have more painful and severe symptoms if a black widow, brown recluse or hobo spider bites you. With proper medical care, most people recover from venomous spider bites.

Living With

When should I call the doctor?

You should call your healthcare provider if you experience:

  • Difficulty breathing.
  • Heart palpitations, a racing pulse or other heart problems.
  • Nausea and vomiting.
  • Severe muscle pain, cramps, weakness or paralysis.
  • Signs of infection, such as fever or yellow discharge from the bite area.
  • Vision problems or severe headache.

What questions should I ask my doctor?

If you have concerns about a spider bite, you may want to ask your healthcare provider:

  • What is the best treatment for my symptoms?
  • How can I prevent future spider bites?
  • Am I at risk for other problems?
  • Should I look out for signs of complications?

A note from Cleveland Clinic

Spiders get a bad rap, but they provide a helpful service by reducing the number of insects on the planet that could destroy crops and land. Spiders really don’t want to bite you. They only bite when they’re trapped or feel the need to defend themselves. Most spider bites are harmless. Your healthcare provider can offer suggestions for alleviating symptoms at home. You should seek immediate medical attention if a black widow, brown recluse or hobo spider bites you.

Last reviewed by a Cleveland Clinic medical professional on 01/08/2021.

References

  • American Academy of Pediatrics (AAP). Spider Bites. (https://www.healthychildren.org/English/health-issues/conditions/from-insects-animals/Pages/Spider-Bites.aspx) Accessed 1/12/2021.
  • American Osteopathic College of Dermatology. Spider Bites. (https://www.aocd.org/page/SpiderBites) Accessed 1/12/2021.
  • Centers for Disease Control and Prevention (CDC) National Institute of Occupational Safety and Health. Venomous Spiders: Symptoms and First Aid. (https://www.cdc.gov/niosh/topics/spiders/symptoms.html) Accessed 1/12/2021.
  • Merck Manual. Spider Bites. (https://www.merckmanuals.com/home/injuries-and-poisoning/bites-and-stings/spider-bites) Accessed 1/12/2021.

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