The thought of getting bitten by a spider can be downright terrifying. Fortunately, most spider bites are harmless and go away on their own, leaving you with nothing more than a little itching. And if you take certain precautions, you can lower the risk of a bite.

Spiders Aren’t Out to Get You

Not only are spiders not aggressive, they're actually rather shy: "Spiders generally don't walk on you and try to bite you," says Andrew Wollowitz, MD, director of the Emergency Department at Montefiore Medical Center in New York City. "There's a lot of fear, but not a lot of action when it comes to spiders."

It's not uncommon for parents to bring a child to the emergency room with a suspected spider bite, only to find out that a spider wasn’t actually the culprit, says Joan Bregstein, MD, Associate Professor of Pediatrics at Columbia University Medical Center and Director of Community Outreach at NY-Presbyterian Morgan Stanley Children's Hospital in New York City. "They think their child has been bitten by a spider but in fact it usually is not from a spider, but from a mosquito. Unless you see the spider on the body, it's generally not a spider bite."

The good news about spiders is that their bites don't transit diseases, as can bites from ticks or mosquitoes. Most spider bites are harmless, and don't even completely penetrate the skin's surface, Wollowitz says.

Poisonous Spiders

While most spiders are harmless to humans, a bite from a poisonous spider, namely a brown recluse or a black widow spider, is more serious. Both spiders are more common in the Southern US, and they prefer warm climates and dry, dark spots where they can catch plenty of flies.

Brown recluse spiders have violin-shaped marking on their backs; their bites leave a red blister surrounded by bluish discoloration. Typically, there is swelling and redness around the bite, and bites may be accompanied by joint stiffness or pain, nausea and vomiting, a body rash, fever, chills, and fatigue.

Black widow spiders have a red hourglass marking on their bellies. Their bites usually leave no visible evidence on the skin, but cause rigid and painful muscles within eight hours. Nausea, vomiting, abdominal pain and cramping, and even trouble breathing can develop.

Treating Spider Bites

Like other bug bites, a bite from a non-poisonous spider can look inflamed and red and may be itchy or cause a painful bump in the skin. If you suspect a spider bite, wash the area with soap and water and apply an ice pack or a cool washcloth to reduce pain and swelling. It should go away in a few days.

If you know that the spider that bit you is poisonous, seek medical attention right away—doctors will most likely treat you with medication.

When to Seek Medical Attention

If the area around the bite looks ulcerated [the skin is open], you develop a rash, or the area looks like it's getting infected, see a doctor, Wollowitz advises. Sometimes a spider bite can cause an allergic reaction with symptoms of chest tightness, wheezing, difficulty breathing, and swelling of the face or mouth. This requires immediate medical attention.

How to Steer Clear of Spiders

To limit your contact with spiders,

  • Make sure your attic and garage are free of spider webs.
  • Wear long sleeves and long pants when you are cleaning the garage or attic, and make sure your children do, too.
  • Encourage kids to wear long sleeved shirts and long pants if they are climbing around a woodpile. (Spiders like hanging out there.)
  • Store firewood outside to avoid bringing spiders into the house.
  • Make sure there are no rocks or lumber right outside your house, since spiders like hanging out in these areas.
  • Install tight-fitting screens on your doors and windows, and seal off any cracks where spiders could enter.

Andrew Wollowitz, MD, reviewed this article.

Sources

"Spider Bites." MedlinePlus. U.S. National Library of Medicine. http://www.nlm.nih.gov/medlineplus/spiderbites.html

"First Aid: Spider Bites." KidsHealth from Nemours. http://kidshealth.org/parent/firstaid_safe/sheets/spider_bites_sheet.html

"Diseases and Conditions: Spider Bites.” The Mayo Clinic. 

"Spider Bites: First Aid." The Mayo Clinic. February 4, 2012. 

Jeffrey Hahn, Phil Pellitteri, Laura Jesse and Donald Lewis. “Common Spiders in and Around Homes.” University of Minnesota Extension. Page revised February 2012.