By: Katherine Mandeville, MD, MSc, FAAP
Spiders might not be your favorite houseguests, but the good news is most of them aren't interested in biting humans. In fact, out of the
50,000+ species of spiders around the world, the ones found in the U.S. are mostly harmless.
While most spiders use venom (poison) to catch their prey, their tiny fangs often can't break through human skin. And unless a spider feels trapped or threatened, it's unlikely to bite at all.
Despite their creepy reputation, spiders are usually more helpful than harmful—snacking on pesky insects like flies and mosquitoes. Still, while most spider bites are harmless, a few can cause serious symptoms. So, it's important to know when a bite might need medical attention.
When to be concerned about spider bites
Most spider bites do not cause serious problems. Reactions may be similar to that of a bee sting, including redness, itching, pain and minor swelling at the site. Some people have more severe reactions to bites, and babies and children may be more affected than adults.
That said, two types of spiders in the United States—the black widow and the brown recluse—can be dangerous.
The brown recluse can cause severe bite wounds, and black widow spiders can cause poisoning. These spiders like warm, dark, and quiet places, such as closets, under sinks, behind furniture and in woodpiles.
Knowing which spiders to watch out for, how to help prevent spider bites and what to do if one happens can help keep your family safe.
Black widow spider
Female black widow spiders are shiny and black, with a red or yellow hourglass shape on their belly. They live in all 48 mainland U.S. states. Only the female black widow spider is dangerous to humans—the male is much smaller and can't bite through human skin.
The bite itself often goes unnoticed or may be felt as a pin-prick. But black widow spider venom is very potent. It attacks the muscles in humans. Symptoms are often severe muscle pain and cramping. Other symptoms can include weakness, nausea, vomiting, sweating, and headache.
Brown recluse spider
The brown recluse spider is also known as the fiddle-back or violin spider. A violin-shaped marking on the back helps to identify it. Both the male and female are dangerous.
It is rare to see the brown recluse spider when it bites because the bite is painless. Reactions to a bite from a brown recluse vary. They range from mild irritation at the bite site to a potentially fatal poisoning.
What spider bites look & feel like
You might notice tiny fang marks
Pain that begins as a dull ache at the bite site. The pain spreads to the surrounding muscles and moves to the abdomen, back, chest, and legs
Blister at the bite site
Mild swelling and a blue-gray mark at the bite surrounded by lightening of skin color
Progressive soft tissue damage; the skin becomes dark blue and then black (necrotic)
First aid care for spider bites
If you suspect that your child has been bitten by a brown recluse or black widow spider:
- Call 911 immediately or go to the nearest emergency department.
General care for spider bites:
Wash the bite area with soap and rinse with water.
Cover the area and apply ice or a cold pack. This will help relieve pain and delay the effects of the venom. Always protect the skin by wrapping ice or a cold pack in a thin cloth.
If your child develops symptoms of infection, like redness, swelling, pus or a warm feeling around the bite, call your doctor or 911 or go to the emergency department.
Tips to prevent spider bitesHere are some simple ways to help protect your family from spider bites: Be careful in areas where spiders like to spend time. Do not let your children play around rock piles or wood piles. Wear gloves when you are working outside in the yard in big piles of logs or leaves.
Shake out your shoes before putting them on, if kept in a mudroom or garage. Shake out blankets and clothing that have been stored in the attic or the basement, or if they have been in a closet for long time. Look carefully behind furniture before reaching around for cleaning.
Remember
About Dr. Mandeville
 Katherine Mandeville, MD, MSc, FAAP, is a pediatric and pediatric emergency medicine board certified physician at Rady Children's Hospital in San Diego and associate clinical professor in the Department of Pediatrics at the University of California San Diego. She serves on Rady's Ethics Committee and is the Emergency Department's Disaster Director, the San Diego County Disaster Advisory Committee, and is the American Academy of Pediatrics (AAP) California Chapter 3 Disaster Ambassador. For several years she has collaborated with the AAP on improving medical care regionally for pediatric patients at community hospitals, serves on quality improvement and peer review committees, is peer reviewer for national journals, and a mentor for medical students and residents.
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