Medical Review By: Thomas Pham, MD
Spider bites are more common than you might think. Garden spiders that get trapped in clothing or under hair may bite two or three times before you flick them off or crush them by scratching. Dermatologists sometimes call these bites “breakfast, lunch, and dinner.”
Fortunately, when it comes to spider bites, the ick factor is almost always worse than the bite. While nearly all spiders produce venom, it’s rarely strong enough to harm humans. Plus, most spiders’ fangs are too short to penetrate human skin.
Bites that produce mild pain or itching can usually be treated with over-the-counter hydrocortisone cream or ointment, cold compresses, and an oral antihistamine if needed to help with itching or swelling.
If you’re unlucky, however, you might encounter one of the two types of spiders in the United States that can seriously harm humans: the black widow and the brown recluse. While they’re not aggressive, they do bite in some circumstances, and there’s a chance you may need emergency treatment if you are bitten.
If possible, take a photo of the spider to help your doctor diagnose the bite and choose a course of treatment.
Black widow spiders
What they look like
Black widows have an almost spherical abdomen and are about half an inch long.
Southern black widow spiders are black with a red hourglass pattern on the underside of the body (females) or red and white markings on the sides of the body (males). In Northern black widows, the hourglass pattern is broken, and there may be a row of red spots on the back and diagonal whitish markings on the side (females). Male Northern black widows usually have faint red and white spots on the underside of the body.
What to know
Black widows can be found anywhere in the United States but are more common in the South and West.
While male black widow spiders don’t bite humans, females can and will attack to defend themselves if you disturb them, especially if they’re in their web protecting their eggs.
You’re most likely to run into a black widow’s web in dark and undisturbed areas, such as woodpiles, eaves, fences, and water meter boxes. When indoors, black widows usually build their webs in cluttered areas, such as a garage or basement.
Spider Bite Symptoms and Treatment
Black widow bites cause a sharp, pinprick-like pain. In many cases, reactions are relatively mild and limited to redness and swelling of the bite area. (You may also notice two tiny red spots that are actually tiny fang marks.) These symptoms appear 15 to 60 minutes after you’re bitten and can be treated at home with cold compresses, over-the-counter pain relievers, elevation (if the bite is on your arm or leg), antibiotic cream, or lotion.
Some people develop a severe reaction and experience signs and symptoms such as stiff and painful muscles, fever, chills, nausea, vomiting, difficulty breathing, weakness, tremors, headache, and belly or back pain. These may develop in as little as 15 minutes after the bite or several hours later. If you have a severe reaction, go to the emergency department or call 911.
Fatalities are rare. Elderly people and small children are more likely to have a severe, possibly life-threatening reaction.
Treatments for severe black widow bites include prescription pain relievers, muscle relaxants, and antivenom.
What they look like
Brown recluse spiders are tan to dark brown with long legs. They often have a darker brown violin shaped-marking just behind their head.
What to know
Brown recluse spiders are typically found in Midwestern and Southern states. They truly are reclusive and would much rather avoid you than attack you. When they do bite, it’s usually because they were trapped against your skin and tried to defend themselves. This may happen if a brown recluse makes its way into your bedsheets, clothes, or shoes.
Brown recluses like to live under rocks, woodpiles, and debris. They’re also well adapted to living indoors, where they prefer dark areas such as basements, attics, closets, and cabinets.
Bite symptoms and treatment
If you’re bitten by a brown recluse, you may not notice right away because the bite is often painless or only mildly painful. In fact, you may never know you’ve been bitten. If symptoms do occur, they typically start three to eight hours after the bite and include redness, tenderness, and a sore at the site of the bite. Other possible symptoms include fever, chills, vomiting, muscle aches, and itching.
Severe symptoms such as extreme pain or trouble breathing require immediate medical attention. Bites in small children, elderly people, and those in poor health also require immediate medical attention.
Brown recluse bites usually heal within three weeks. However, in about 10% of cases, a bite can cause tissue death in the affected area. An ulcer or blister with a blue, purple or black center develops and may become infected.
Treatments for severe brown recluse bites include antibiotics, antihistamines, and steroids. Some victims need surgery to remove the damaged tissue around the wound.
At-home treatments for mild bites are the same as those for mild black widow bites.
Hobo and yellow sac spiders: Cause for concern?
These two types of spiders have a nasty reputation. It was once thought that their bites, like that of a brown recluse, could lead to tissue death. But researchers now say there’s no evidence to support that idea. While hobos and yellow sacs do bite occasionally, you’re unlikely to experience symptoms beyond minor pain, swelling, and redness.
Article Written By: Jessica Brown, a health and science writer/editor based in Brooklyn, New York. She has written for Prevention magazine, jnj.com, BCRF.org, and many other outlets.