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The most common indoor spider bite is that of the pale sac spider, which spins a silken sac web in the corners of ceilings and walls. The bad news is that they’re aggressive, abundant, and like to hang out where people do: in the house and garden.  The good news about sac spiders is that their venom is not very toxic to people.

The most dangerous spiders in the U.S. are black widows and brown violin or brown recluse spiders. A black widow has a distinctive hourglass-shaped mark on the belly. A brown recluse has a violin-shaped marking on the back. If you’re bitten by either, it’s a medical emergency but rarely fatal.

Both black widows and violin spiders prefer warm climates. The black widow lives primarily in the Southern and Western United States. The violin spider is most commonly found in the Midwestern and Southern states. Both spiders like dark, dry, undisturbed places with easy access to flies.

Remember that most spiders, even black widows, usually bite out of self-defense -- if they’ve been squeezed or sat on by something much bigger, like you.

Preventing Spider Bites

To protect against spider bites, wear gloves, long sleeves, and long pants when working in areas where they like to hide. Watch where you put your hands and shake off clothing before you put it on or go inside.

Indoors, sweep, mop, or vacuum webs and spiders regularly. In attics, basements, and garages, place boxes off the floor and away from walls and tape them closed.  Seal off cracks and gaps where spiders may enter your home to discourage them and their prey. Clean up clutter and trim growth near the house.

Strickman advises against routinely spraying your house for spiders. Spiders are helpful, he points out -- eating flies and even fleas. It’s usually just as effective to clean out the webs and kill the spiders you see.

Treating Spider Bites

The first step to treating a spider bite is to identify the type of spider, if possible.

The black widow’s bite feels like a pinprick. At first, it may create red marks and a little swelling. Within a few hours, you may feel intense abdominal pain, stiffness, fever, and nausea. Severe muscle cramps, nausea, vomiting, seizure, and a rise in blood pressure may follow soon after.  Life-threatening reactions are usually seen only in the elderly and small children.  Anti-venom medicine is available. If possible, bring the spider with you so the doctor can identify it.

The brown recluse spider bite stings and may cause redness. Over time, this turns into a blister and then an ulcer. Symptoms can range from mild fever and rash to nausea and listlessness.

For a black widow or violin spider bite:

  • Clean the area with soap and water.
  • If the bite is on an arm or leg, elevate it to help prevent swelling.
  •  Put a damp, cool cloth on the site.
  • See a doctor immediately.