Does Cedar Actually Keep Spiders Away?

Cedarwood essential oil has shown genuine repellent effects against at least one spider species in laboratory testing, but the evidence is thin, limited to a handful of studies, and far from proving that a cedar chest or a few cedar blocks in your closet will keep spiders out. The reputation of cedar as a spider deterrent mostly piggybacks on its much longer and better-documented history of repelling moths and other textile pests. What the science actually says about spiders specifically is more interesting, and more limited, than most people expect.

The Study That Directly Tested Cedarwood Oil on Spiders

The most direct piece of evidence comes from a 2025 study that tested several essential oils against the wolf spider Pardosa hortensis using binary choice tests, where spiders could move toward or away from a treated area. Cedarwood oil was one of five essential oils that significantly deterred spider activity, alongside catnip, cinnamon, citronella, and clove.¹ The researchers attributed the repellent effects to chemical compounds like eugenol, β-caryophyllene, and geraniol found in these oils.

That’s encouraging, but context matters. This was one species of ground-dwelling spider, tested in a controlled lab environment, with concentrated essential oil. Wolf spiders are active hunters that roam across surfaces, which makes them relatively easy to test in a two-choice setup. Whether cedarwood oil would have the same effect on web-building spiders that sit in one place for weeks, or on species you’re more likely to encounter indoors, remains untested. The finding is real, but extending it to “cedar keeps spiders away from your house” requires a leap the data doesn’t support yet.

Why “Cedar” Could Mean Almost Anything

One of the biggest problems with the claim that cedar repels spiders is that “cedar” refers to a remarkably wide range of trees. True cedars belong to the genus Cedrus, but the label gets applied to species of juniper, cypress, thuja, cryptomeria, and several other genera across multiple continents.² The oils from these trees are chemically distinct from one another, sometimes dramatically so.

Eastern red cedar (Juniperus virginiana), the species most commonly used in American cedar closets, cedar chests, and cedar planks, produces oil rich in cedrol and cedrenes. True cedars from the Himalayas and Atlas Mountains are dominated by himachalenes and atlantones, which are different compounds entirely.² When someone says “cedar repels spiders,” the question is immediately: which cedar? The chemical profile of the wood in your closet may have little in common with the oil used in a study, or with the cedar shavings your grandmother swore by.

Cedrol, one of the signature compounds in eastern red cedar, can make up roughly 16 to 25 percent of the essential oil from J. virginiana.³ It’s a sesquiterpene alcohol with a strong woody scent and documented biological activity, including interactions with cell membranes and nervous system pathways. The cedrenes, which contribute to cedar’s distinctive aroma, are highly lipophilic and can interact with lipid membranes or ion channels in arthropods.³ So there are plausible chemical reasons why cedarwood oil could bother arthropods. But plausible and proven are two different things, and the chemical variability between cedar species means that any repellent effect would depend on which tree the product came from.

Where the Cedar-Repels-Bugs Reputation Actually Comes From

People have been stuffing cedar shavings into storage containers for centuries, but the original target was moths, not spiders. Cedarwood shavings, along with camphor and tobacco leaves, were among the earliest materials used to protect stored wool and textiles from insect damage.⁴ The logic was straightforward: moth larvae eat wool fibers, and something about cedar seemed to discourage them.

Over time, the idea that cedar was broadly “anti-bug” expanded well beyond moths. Cedar closets, cedar hangers, cedar drawer liners, and cedar shoe trees all trade on this association, and marketing has blurred the line between what cedar was originally used for and what it can actually do. The jump from “repels moths in a sealed storage environment” to “repels spiders in your home” happened in popular culture, not in any laboratory. Spiders don’t eat textiles and have very different biology from moths, so there’s no particular reason to assume what works on one would work on the other without testing it directly.

How Spiders Sense Chemicals in Their Environment

For any repellent to work, the target animal needs to detect the chemical and find it aversive. Spiders have a somewhat unusual sensory setup compared to insects. Research on orb-weaver spiders (Argiope species) has identified specialized sensory structures on their leg tips called tarsal tip-pore sensilla. These sensilla contain between 2 and 22 chemoreceptive cells, each with elongated dendrites reaching a pore at the tip of the structure.⁵ Interestingly, researchers found no wall-pore sensilla on these spiders, which raises the possibility that a single type of sensillum handles both taste and smell.

This matters for understanding repellent effects because it suggests spiders may detect chemicals primarily through contact with surfaces rather than by sniffing the air the way many insects do. If that’s the case, an aromatic cedar plank across the room might not register with a spider the way it would with a flying moth. The spider would need to walk over or very near a treated surface to encounter the chemical compounds. That’s a meaningful distinction for anyone hoping that hanging a cedar block in the corner of a room will create a spider-free zone: the volatiles floating through the air may not be reaching the spider’s sensory organs in the way you’d want them to.

What Has Actually Been Tested Against Spiders

The broader literature on spider repellents is surprisingly sparse. A well-designed 2018 study tested three of the most commonly recommended natural spider repellents found across internet advice sites: horse chestnuts, mint oil, and lemon oil. Two species of web-building spiders, the brown widow (Latrodectus geometricus) and the European garden spider (Araneus diadematus), showed strong avoidance of chestnuts and mint oil but no response whatsoever to lemon oil.⁶ A third species, the false widow (Steatoda grossa), was not repelled by mint oil and only showed a slight tendency to avoid chestnuts.

A few things jump out from this. First, the study did not test cedar at all, despite cedar being one of the most frequently cited natural spider repellents online. The researchers chose to test the three substances that appeared most often in internet advice, and cedar apparently didn’t make that cut. Second, even among the substances that were tested, results varied by spider species. Mint oil worked well on two species but not a third. That species-level variation is a consistent theme in the repellent literature and should temper anyone’s confidence that a single product will work on all the spiders in their home.

When you put the 2018 and 2025 studies side by side, mint oil has the most consistent spider-specific evidence across multiple species, followed by chestnuts for web-building spiders. Cedarwood oil has positive results from one study on one species of ground-hunting spider. That doesn’t make cedar useless, but it places it behind other natural options in terms of how much direct spider evidence exists.

Cedar’s Track Record Against Other Arthropods

While the spider evidence is limited, cedarwood oil has been tested more extensively against other arthropods, including some that are closely related to spiders. A study on hard ticks (which, like spiders, are arachnids) found that CO₂-derived cedarwood oil repelled nymphs of several tick species in a dose-dependent manner. Blacklegged tick nymphs were the most sensitive, followed by brown dog ticks, American dog ticks, and lone star ticks.⁷ The same cedarwood oil was also toxic to several tick species at higher concentrations over 24 hours of exposure.

Field tests on little fire ants in a Hawaiian macadamia orchard found that chopsticks treated with cedarwood oil had significantly fewer ants than untreated controls or those treated with mineral oil alone. Pure cedrol, though less effective than the full oil, still reduced ant numbers compared to controls.⁸ That finding is worth noting because it suggests the full essential oil works better than any single purified compound, which is consistent with how many essential oils function: the whole mixture is more repellent than the sum of its parts.

The tick and ant data confirm that cedarwood oil has real biological activity against arthropods. It’s not pure folklore. But ticks and ants are not spiders, and repellent effects don’t automatically transfer across taxonomic groups. What the broader arthropod data give you is a reason to take the spider hypothesis seriously, not a reason to assume it’s been proven.

The Gap Between Essential Oil and Cedar Furniture

Perhaps the biggest disconnect in the whole “cedar keeps spiders away” claim is between the concentrated essential oil used in studies and the cedar products people actually put in their homes. When researchers test cedarwood oil, they’re working with concentrated extracts applied directly to surfaces in enclosed testing arenas. A cedar plank in your closet is a fundamentally different delivery system.

Fresh cedar wood does release volatile compounds into the surrounding air, which is why it smells so distinctive. But that scent fades over time as the surface oxidizes and the volatile compounds evaporate. Anyone who has had a cedar closet or cedar chest for more than a year or two knows that the smell weakens considerably. The fire ant field study noted that the full cedarwood oil outperformed pure cedrol, suggesting that the volatile mixture matters and that losing some of those compounds to evaporation could meaningfully reduce effectiveness.⁸

Sanding the surface of cedar wood can temporarily restore some of the scent by exposing fresh material underneath, which is a common recommendation from cedar product manufacturers. But this is a diminishing-returns strategy. You can only sand so many times before the wood is too thin or uneven to function. Cedar essential oil applied to surfaces or diffused into the air would deliver a higher concentration of active compounds than old cedar planks, but it would also evaporate and need reapplication, probably frequently.

For comparison, synthetic insect repellents like DEET or permethrin are formulated specifically for sustained release and have decades of testing behind them for specific target organisms. Natural essential oils, cedar included, have neither the formulation technology nor the regulatory testing data to compete with synthetic options on reliability or duration. That doesn’t make them worthless for someone who prefers natural approaches, but it’s worth being realistic about what you’re getting.

What Would Actually Keep Spiders Out of Your Home

If your goal is fewer spiders indoors, the honest answer is that environmental management does more than any repellent, natural or synthetic. Spiders follow their food: if you have flies, gnats, or other small insects in your home, spiders will come looking for a meal. Reducing insect populations by managing outdoor lighting (switching to yellow or sodium vapor bulbs that attract fewer bugs), sealing cracks and gaps around windows and doors, and keeping vegetation trimmed back from the house exterior will reduce spider entry more effectively than any scented product.

Spiders also favor undisturbed spaces. Regular cleaning, vacuuming corners and ceilings, and clearing out cluttered storage areas removes existing webs and egg sacs. A spider that has its web destroyed repeatedly will often relocate. These housekeeping measures aren’t glamorous, but they address the reasons spiders chose your home in the first place.

If you still want to try cedar as a supplemental measure, essential oil diffused near entry points or applied to cotton balls and placed in corners is likely to deliver more compound to the immediate area than cedar blocks or hangers. Refreshing the application every few days would keep the concentration in a range that at least has a plausible chance of reaching the threshold that deterred wolf spiders in the lab study. Just don’t expect it to create an invisible force field around your home. The lab evidence shows deterrence, not a hard barrier, and it was demonstrated under tightly controlled conditions with concentrated oil.

Cedarwood Oil and Pets

One consideration that rarely comes up in the “natural spider repellent” conversation is pet safety. Cedarwood oil is one of the essential oils sometimes marketed as safe for use around dogs, and it even appears in some natural flea and tick products. But essential oil safety varies significantly between animal species. Cats, in particular, lack certain liver enzymes that metabolize compounds found in many essential oils, including some terpenes present in cedarwood oil. Diffusing concentrated essential oils in a home with cats carries real risk, and veterinary sources generally recommend caution with any essential oil around feline companions.

This is worth knowing because the same person who searches for natural spider repellents often does so specifically because they’re trying to avoid synthetic chemicals they consider harsh or dangerous. Swapping a synthetic pesticide for a concentrated essential oil isn’t automatically a trade-up in safety, especially if you have pets or small children. The “natural” label on essential oils can obscure the fact that these are biologically active chemical mixtures with genuine effects on living organisms. That biological activity is precisely why they can repel arthropods, and it’s also why they deserve the same respect you’d give any other chemical product in your home.

What the Research Still Needs to Address

The spider repellent field, taken as a whole, is strikingly understudied. The 2018 study on chestnuts and mint oil explicitly noted that they were testing the first scientific evidence for or against claims that had been circulating online for years without anyone bothering to check.⁶ The 2025 wolf spider study is one of the first to systematically screen multiple essential oils against a spider species and identify which compounds might be responsible for the effect.¹

What’s missing is almost everything that would make this useful in practice. Nobody has tested cedarwood oil against the spider species that most commonly appear in homes, like common house spiders, cellar spiders, or cobweb spiders. Nobody has tested whether the concentrations achievable through passive wood exposure or casual diffusion reach the thresholds needed for repellency. Nobody has done a field trial in actual homes to see if cedarwood oil reduces spider encounters compared to an untreated control. And nobody has established how long any repellent effect lasts under realistic conditions with air circulation, temperature variation, and the gradual breakdown of volatile compounds. Until those studies happen, the honest answer to whether cedar keeps spiders away is: maybe, under specific conditions, for some species, if the concentration is high enough, but we genuinely don’t know yet for the situations most people care about.

1
PubMed. Repellent effect of selected essential oils against the wolf spider Pardosa hortensis (Araneae: Lycosidae)
2
PubMed Central. Cedarwood Oils: The Wood Essential Oil Compositions from Trees Known as “Cedar”
3
Exploration of Drug Science. Cedarwood essential oil (Cedrus spp.): a forgotten pharmacological resource with emerging therapeutic potential
4
Elsevier. A comprehensive review on moth repellent finishing of woolen textiles
5
PubMed. Ultrastructure of chemosensory tarsal tip-pore sensilla of Argiope spp. Audouin, 1826 (Chelicerata: Araneae: Araneidae)
6
Journal of Economic Entomology. Natural Compounds as Spider Repellents: Fact or Myth?
7
PubMed Central. Repellency and toxicity of a CO2-derived cedarwood oil on hard tick species (Ixodidae)
8
Academia. Field Test for Repellency of Cedarwood Oil and Cedrol to Little Fire Ants