There is no scientific evidence that baking soda kills spiders. While baking soda appears on many lists of “natural spider remedies,” it functions primarily as a repellent when sprinkled in dry form, not as a lethal substance. No published research demonstrates that sodium bicarbonate is toxic to spiders on contact or through ingestion.
What Baking Soda Actually Does to Spiders
Baking soda is commonly grouped with natural spider deterrents like lemon juice and tobacco solutions. The idea is that spiders avoid walking through or across dry baking soda, possibly because the gritty alkaline powder irritates their bodies or disrupts sensory cues they use to navigate. But “repelling” and “killing” are very different outcomes. Spiders that encounter a line of baking soda along a windowsill may turn around, but they won’t die from the exposure.
Some DIY pest control guides suggest mixing baking soda with vinegar to create a spray. The logic sounds plausible: vinegar’s acetic acid burns spiders on contact, and baking soda adds an extra punch. In reality, combining baking soda with vinegar triggers a neutralization reaction. The acid and the base cancel each other out, producing water, carbon dioxide gas, and sodium acetate, a mild salt. The resulting mixture is less acidic than straight vinegar, meaning you’ve actually diluted the one ingredient that could harm a spider.
Why Vinegar Works Better on Its Own
If you’re looking for a contact spray, plain white vinegar mixed with equal parts water is more effective than any baking soda combination. The acetic acid in vinegar burns a spider’s exoskeleton on direct contact. The key phrase here is “direct contact.” You need to hit the spider with the spray for it to work. It won’t create a lasting barrier the way a chemical pesticide would, and it won’t affect spiders hiding in wall voids or attic spaces you can’t reach.
This makes vinegar spray a reactive tool, useful for the spider you can see right now, but not a solution for an infestation or a way to prevent spiders from entering your home in the first place.
Natural Repellents With Actual Research Behind Them
If you’re drawn to baking soda because you want a chemical-free approach, a few natural options have stronger evidence supporting them. A 2018 study tested peppermint oil, lemon oil, and chestnuts against multiple spider species. Peppermint oil and chestnuts both strongly repelled two of the three species tested. Lemon oil, despite being widely marketed as a spider repellent, showed no measurable effect on any species in the study.
To make a peppermint oil spray, the National Association for Holistic Aromatherapy recommends 10 to 15 drops per ounce of water. Spray it around door frames, window edges, and corners where spiders tend to build webs. You’ll need to reapply every few days as the scent fades. Chestnuts placed along baseboards or windowsills may also discourage spiders from settling in, though this approach is less practical for large areas.
A separate 2009 study found that a commercial product containing garlic, clove, and cottonseed oil killed over 90 percent of the mites it was tested on. While mites aren’t spiders, both are arachnids, and the results suggest that concentrated essential oil blends can have real pest control effects when formulated properly.
Pet Safety With Baking Soda
One reason people reach for baking soda is the assumption that it’s completely safe around pets. That’s mostly true in small amounts, but worth understanding in detail if you’re sprinkling it around your home.
Baking soda becomes toxic to dogs and cats at roughly 2 to 4 teaspoons per kilogram of body weight. For a small dog or most cats (under 10 pounds), that threshold is as little as a third of a tablespoon. Symptoms of overconsumption include vomiting, diarrhea, tremors, seizures, and disorientation, and they can appear within three hours. A thin line of baking soda along a baseboard is unlikely to cause problems, but if you’re dusting it liberally across floors or in areas where a pet might lick or dig, the risk increases.
Peppermint oil carries its own risks for pets, particularly cats, who lack the liver enzymes to process certain essential oil compounds. If you have cats, keep peppermint spray to areas they can’t access, or stick with physical exclusion methods like sealing cracks and gaps.
What Actually Reduces Spiders in Your Home
Spiders go where their food is. If you have spiders, you almost certainly have other insects providing a food source. Reducing overall insect populations through better exterior lighting choices (yellow bulbs attract fewer bugs), sealing gaps around doors and windows, and clearing clutter where insects hide will do more than any repellent spray.
Removing existing webs regularly also discourages spiders from staying. Most species rebuild in the same spot out of habit, and repeated web removal signals that the location isn’t stable. Sticky traps placed along baseboards can catch wandering spiders and also help you identify what species you’re dealing with. If you’re seeing large numbers of brown recluse or black widow spiders, that’s a situation where professional pest control is worth the investment, since no home remedy reliably controls dangerous species.
Baking soda is cheap, nontoxic in small amounts, and might mildly discourage a spider from crossing a specific spot. But if you’re hoping it will kill spiders or solve an ongoing problem, you’ll be disappointed. Your time and effort are better spent on the approaches above.