Everything You Need to Know

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On June 4, 2025

While spiders are often blamed for large or unusual skin lumps, sores, or lesions, experts say that spiders bite far less often than most people assume.

“People wake up in the morning, find a red mark, and immediately call it a spider bite,” says Rick Vetter, a retired entomologist at the University of California in Riverside. But most of the skin issues that people pin on spiders are actually other types of bug bites or skin problems, he says.

What do legitimate spider bites look like? That depends on the type of spider, Vetter says.

Brown Recluse Spiders These bites sting, and they can resemble anything from small blisters — similar to mosquito bites — to large, rotting flesh sores, Vetter says. Along with a wide variety of skin symptoms, brown recluse bites can cause chills, fever, nausea, and other flu-like symptoms. The venom in a brown recluse’s bite is poisonous and, in some rare cases, can result in a coma, kidney failure, or even death.

Black Widow Spiders These bites can cause skin lesions, ranging from small red marks to angry, streaky red patches of inflamed or oozing skin. “But most of the reaction will be on the inside,” Vetter says. Black widow bites contain potentially deadly amounts of venom and tend to be painful right away. While that pain starts around the bite site, within an hour it often spreads to the chest or abdomen, depending on whether the bite occurred on the upper or lower body. Other symptoms can include everything from headaches, muscle weakness, and difficulty breathing to seizures, numbness, and painful muscle cramps.

Hobo Spiders, Wolf Spiders, House Spiders The bites of these and other domestic spiders do not contain venom that is of medical concern to humans, Vetter says. They can bite, but, he adds, the result is likely to be similar to a bee sting — meaning a sharp pain, followed by a painful, swollen red lump at the bite site.

For nonvenomous spider bites, washing the injury with soap and water, applying ice, and taking over-the-counter pain or anti-itch medications are the best courses of action. But if you experience any of the systemic symptoms mentioned above — headaches, muscle weakness, flu-like symptoms — seek medical attention immediately.

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