Why You Should Always Think Twice Before Killing a Spider in Your House

The typical house spiders that hang out in the corners of your home are generally considered harmless—and even helpful in some cases. "When you kill a spider, you’re essentially removing a built-in, chemical-free pesticide that’s protecting your home for you," explains certified entomologist Kris Bagnara. "They’re nature’s pest-control technicians and most never bother the people they live alongside."

Here, our experts explain the difference between helpful and harmful spiders, how to differentiate between them, and why it's best to avoid killing the innocuous spiders you may find in your home.

How to Differentiate Helpful vs. Harmful Spiders

Two of the most concerning spiders in the U.S., according to award-winning entomologist Dr. Tracy Ellis, are widows and recluses—both capable of delivering medically significant bites. “These bites typically happen when a person unknowingly presses against the spider—often by reaching into a hidden or cluttered space,” she says. “People cleaning or reorganizing indoor or outdoor storage areas, attics, sheds, or other sheltered spots are at the highest risk of encounters.”

Both species prefer long-term, undisturbed hiding places. "In the southern U.S., residents should watch for shiny black widows marked with a red or orange hourglass on the underside," details Ellis. "The brown recluse is a large, plain brown spider roughly the size of a quarter," she says, adding that those in the lower Midwest, Texas, and the Southeast should be on particular lookout.

Unfortunately, harmless hobo spiders and wolf spiders are sometimes mistaken for recluses. "One behavioral clue is that hobo and wolf spiders are more likely to be found out in the open inside homes, unlike the reclusive brown recluse," Ellis explains. "As a general rule, spiders encountered in active, disturbed areas are unlikely to be dangerous widows or recluses."

Why You Should Never Kill Harmless Spider Species

Harmful species are way less common indoors, Bagnara says, and even so, they aren’t out to get you. "They generally avoid humans and will only bite if they feel pressure when they're trapped or startled," he says.

Meanwhile, household and garden spiders are beneficial pest controllers that should be left alone or carefully relocated. "By killing the spider, you’re removing a tireless, around-the-clock predator that helps protect your home and garden from other insects that are likely pests," says Ellis.

Spiders choose places that offer a steady supply of prey, which means other insects are likely making their way inside if you're spotting spiders. So you see, most spiders you find indoors are quietly doing a job you’d probably rather not do yourself. "They help manage pests that aren’t just irritating," Bagnara says, "but ones that can spread bacteria or bite." 

Alternatives to Squishing Spiders

If you do find a spider indoors, choose a humane removal method. “Place a clear cup or jar over it, slide a piece of stiff cardboard underneath, and carry it outside for release,” Ellis says. “If you’re not comfortable doing it yourself, ask a friend or family member who is.”

For a stronger deterrent, Bagnara suggests a few ways to discourage or remove spiders without harsh chemicals.

• Diatomaceous earth: Food-grade DE is a fine powder that damages a spider’s protective outer layer, causing them to dry out naturally. Lightly dusting along baseboards, window sills, or travel routes you’ve noticed are generally the best places to place it. Keep in mind, it’s not instant and has to remain dry to work. Wear a dust mask when applying.
• Baking soda and cornstarch dust: A pantry-friendly option of equal parts baking soda and cornstarch creates a fine dust that can clog joints and slowly dehydrate a spider. Similarly to DE, you’ll want to lightly dust along baseboards, window sills, or travel routes you’ve noticed. It works best dry and needs reapplication after cleaning.
• Essential oil spray: Mix 10 to 15 drops of peppermint or citrus essential oil with a cup of water and a few drops of dish soap. Then, spray directly on the spider. As a bonus, the scent will repel any new unwelcome pests to the area.

How to Prevent Spiders

Make your home and yard less attractive to spiders by removing the reasons they choose it as a hunting ground—namely, their insect prey. “Focus first on controlling the pests that may be drawing them in,” Ellis says. “A licensed pest control professional can help identify any underlying infestations and recommend solutions.” 

Address structural issues by sealing cracks around windows and doors with caulk, installing door sweeps, and repairing gaps that allow insects inside. “Reduce insect attraction at night by limiting outdoor lighting or switching to yellow LED bulbs, which draw fewer bugs,” Ellis suggests. “Maintain a clean interior by vacuuming corners and baseboards weekly to remove webs, egg sacs, and hidden prey.”