Giant house spiders (Eratigena atrica) can technically bite, but they almost never do, and when they manage it, the result is roughly on par with a mild bee sting for most people. These fast, leggy spiders that sprint across living room floors every autumn look alarming, yet researchers who study spider venom broadly conclude that the vast majority of spider species are essentially harmless to humans. The giant house spider fits squarely in that harmless category, though its size and speed have earned it an outsized reputation.
Can a Giant House Spider Actually Pierce Your Skin?
A fair question, because many common house spiders physically cannot bite through human skin at all. Worldwide, researchers estimate that only around 50 spider genera possess chelicerae (the fang-tipped mouthparts spiders use to deliver venom) large enough to penetrate human skin.1Scientific Reports. Emotions triggered by live arthropods shed light on spider phobia The giant house spider, with a body length that can reach about 18 mm and a leg span of up to 75 mm, is large enough to make the cut. Its chelicerae can, under the right circumstances, break through skin on thinner areas like the forearm or the back of the hand.
That said, having the physical equipment to bite and actually choosing to use it are different things. Giant house spiders are not aggressive toward people. They rely on funnel-shaped webs to catch prey and generally flee when disturbed. The scenario where a bite happens almost always involves the spider being pressed against skin with no escape route, such as being trapped inside clothing, bedding, or a shoe. Defensive bites are a last resort, not a hunting behavior directed at humans.
What Their Venom Does (and Doesn’t Do)
Giant house spiders do produce venom. A 2023 study used Eratigena atrica as a model organism to examine how venom composition changes depending on how it is extracted, finding distinct protein profiles and differing potency against crickets depending on the extraction method.2Toxicon. Venom extraction method influences venom composition and potency in the giant house spider Eratigena atrica This confirms that the venom is biologically active and effective against small invertebrate prey. But potency in crickets does not translate to danger for a human weighing thousands of times more.
If you are bitten, you can expect localized effects: a brief sharp pain at the bite site, mild redness, and possibly minor swelling. These symptoms are comparable to what you might experience from a mosquito bite or minor wasp sting and typically resolve on their own within a day or two. There is no evidence that giant house spider venom causes tissue death (necrosis), systemic illness, or any reaction requiring medical treatment in healthy adults. Of the roughly 50 spider taxa whose bites have been clinically evaluated, most cause only modest, short-lived effects.1Scientific Reports. Emotions triggered by live arthropods shed light on spider phobia The giant house spider sits comfortably in that mild category.
The only people who should exercise extra caution are those with known allergies to arthropod venoms or compromised immune systems. Allergic reactions to spider venom are rare but possible, just as they are with insect stings. If you notice symptoms spreading well beyond the bite site, such as hives, difficulty breathing, or significant swelling, seek medical attention. For the overwhelming majority of people, though, a giant house spider bite is a minor inconvenience at worst.
Why They Get Confused with the Hobo Spider
Much of the fear around giant house spiders is borrowed from another species: the hobo spider (Eratigena agrestis). These two spiders are close relatives in the same genus, share a similar body shape and brownish coloring, and both build funnel webs. To an untrained eye they look nearly identical, and they share overlapping habitat in parts of Europe and the Pacific Northwest of North America, where the hobo spider was introduced in the early twentieth century.3The Canadian Entomologist. Life-history data for the funnel weavers Eratigena agrestis and Eratigena atrica in the Pacific Northwest of North America
The hobo spider gained a reputation in the 1980s for causing necrotic wounds, and that reputation has proven stubbornly persistent even though subsequent research has largely undermined it. The initial claims of necrotic arachnidism were based on a small number of cases in the northwestern United States, and later reviews questioned whether the hobo spider’s venom can actually cause tissue death in humans. The CDC eventually removed the hobo spider from its list of venomous spiders of medical concern. Still, the lingering association between “big brown funnel web spider” and “dangerous bite” means that giant house spiders, which are even larger than hobo spiders, inherit a fear they have not earned.
Telling the two apart without magnification is genuinely difficult. Giant house spiders tend to be bigger, with longer legs relative to body size, and they lack the distinct chevron pattern on the abdomen that hobo spiders sometimes display. But these differences are subtle enough that even pest control professionals can misidentify them. If you find a large brown spider in a funnel web and want a definitive identification, a clear photograph sent to an entomology extension service is far more reliable than a Google image search.
Most “Spider Bites” Are Not Spider Bites
Perhaps the most important thing to know about spider bites in general is that they are wildly over-reported. A study of patients who came to an emergency department believing they had been bitten by a spider found that only about 4% actually had spider bites. Roughly 86% of the suspected spider bites turned out to be infections, primarily skin abscesses caused by bacteria like MRSA.4PubMed. Arachnid envenomations and other suspected spider bites presenting to the emergency department Another 5% were bites from other animals entirely. The patients were not making things up; they genuinely believed a spider was responsible. But in most cases, no spider was seen at the time of the bite, and the skin lesion was caused by something else altogether.
This matters because misattributing a bacterial infection to a spider bite can delay proper treatment. If you develop a red, swollen, warm, or painful skin lesion and you did not actually see a spider biting you, the most likely cause is a bacterial skin infection, not venom. Antibiotics rather than antivenin are what you need. The instinct to blame a spider is understandable, but doctors who specialize in arachnid envenomation have been trying for decades to push back against it.
The confusion is compounded by a separate but related myth: that spider bites frequently introduce dangerous bacteria into the wound. A review of the published literature on spider envenomations concluded that the evidence for spiders acting as vectors for bacterial infections is thin. The mere presence of bacteria on a spider’s fangs does not mean those bacteria reliably transfer into a bite wound or cause infection.5Toxicon. Spider Bites Highly Unlikely to Cause Bacterial Infections A spider bite that becomes infected is more likely the result of the person scratching the site afterward than the spider injecting bacteria.
Where Giant House Spiders Live
Giant house spiders are native to central and western Europe, where they are among the most common large spiders found indoors. Their natural habitat is dark, sheltered spaces: under logs, in rock crevices, and in caves. Human buildings offer an irresistible substitute, which is why these spiders have been living alongside people in Europe for centuries.
They have also established themselves in parts of North America, particularly the Pacific Northwest. Both Eratigena atrica and its close relative Eratigena agrestis were introduced to the region in the early 1900s and have spread steadily since.3The Canadian Entomologist. Life-history data for the funnel weavers Eratigena agrestis and Eratigena atrica in the Pacific Northwest of North America In the UK, the giant house spider is probably the species most responsible for autumnal spider panics: males leave their webs in late summer and early autumn to search for mates, and their wandering takes them across open floor space at surprising speed. That combination of size and sudden, rapid movement in your peripheral vision is what triggers most encounters.
Outside of Europe and the Pacific Northwest, you are unlikely to run into Eratigena atrica specifically, though every region has its own large house-dwelling spider species that provokes similar anxiety. The advice about danger level is broadly transferable: the vast majority of spiders that show up indoors around the world are harmless.
Practical Steps If You Find One
If a giant house spider in your home bothers you, the simplest approach is the glass-and-card method: place a glass or container over the spider, slide a stiff piece of card underneath, and carry the whole assembly outside. Giant house spiders are fast but not particularly evasive once contained. Releasing them near an exterior wall, a woodpile, or any sheltered outdoor spot gives them the best chance of surviving and keeps them out of your living space.
For people who find spiders regularly and want to reduce encounters:
- Seal entry points: Check window frames, door sweeps, and gaps around pipes. Spiders do not need large openings.
- Reduce clutter at ground level: Stacked boxes, piles of clothing on the floor, and unused shoes are prime hiding spots.
- Remove other insects: Spiders go where the food is. If your home has flies, gnats, or other small insects, spiders will follow. Addressing the prey problem often addresses the spider problem.
- Turn off outdoor lights near doors: Lights attract flying insects, which attract spiders to the perimeter of your home, which means more of them wander inside.
Killing giant house spiders is of course an option but a counterproductive one in most situations. These spiders consume significant numbers of flies, mosquitoes, and other household pests. A single giant house spider living behind a bookshelf is doing more pest control work than most plug-in devices claim to offer. If you can tolerate their presence, they are net beneficial housemates.
If You Think You Have Been Bitten
For a confirmed or suspected giant house spider bite where you actually saw the spider, clean the area with soap and water and apply a cold compress to manage any swelling. Over-the-counter pain relief can help if the bite site is sore. Monitor the area for a couple of days. If it improves steadily, which it almost certainly will, no further action is needed.
Seek medical attention if the redness expands significantly, if you develop a fever, or if the wound begins to look like an infection rather than a simple bite. Remember that these symptoms are far more likely to indicate a bacterial skin infection that coincidentally appeared than a reaction to spider venom. Being honest with your doctor about whether you actually saw a spider or are guessing based on the appearance of the wound helps them reach the right diagnosis faster.
Do not attempt to capture and bring the spider with you to the hospital unless it is already dead and easily collected. Chasing a spider around a room after being bitten adds stress without meaningfully changing your medical treatment, since giant house spider bites do not require species-specific intervention.
Why These Spiders Scare People Anyway
Arachnophobia, the specific and sometimes debilitating fear of spiders, affects somewhere between 3% and 6% of the general population.1Scientific Reports. Emotions triggered by live arthropods shed light on spider phobia This makes it one of the most common animal phobias, far out of proportion to the actual threat spiders pose. Researchers estimate that only about 0.5% of all spider species are potentially dangerous to humans, and even among those, severe outcomes are uncommon.1Scientific Reports. Emotions triggered by live arthropods shed light on spider phobia
Giant house spiders are particularly good at triggering this fear because they hit several arachnophobic pressure points at once. They are large enough to be instantly visible from across a room. They move fast, which triggers a startle response. They appear suddenly, often at night. And they tend to show up during a concentrated period in early autumn rather than being spread throughout the year, which creates the impression of an invasion rather than a steady background presence.
The fear response is real and worth taking seriously, even though the spider is harmless. For people with genuine arachnophobia, knowing that the spider cannot hurt them does not necessarily reduce the fear, because phobias operate below the level of rational risk assessment. Cognitive behavioral therapy and exposure therapy have strong evidence for reducing arachnophobia. If encountering spiders in your home causes genuine distress rather than just mild discomfort, speaking with a therapist who specializes in specific phobias is more useful than any spider-proofing strategy.
Giant House Spiders as Pest Controllers
One underappreciated dimension of sharing your home with Eratigena atrica is their ecological role indoors. Giant house spiders are generalist predators that eat whatever stumbles into their funnel webs or crosses their path during nighttime hunting. Their diet includes flies, moths, mosquitoes, earwigs, cockroaches, and even other spiders. In areas where the hobo spider has become established, giant house spiders may actually displace them through competition, which is a net positive from a human perspective given the hobo spider’s worse (if mostly undeserved) reputation.
Their webs tend to be tucked into corners, behind furniture, and in basements, places where humans rarely look but where pest insects frequently travel. A giant house spider maintaining a web in your garage is intercepting insects you would otherwise encounter. They are not aggressive about web placement and generally avoid high-traffic areas, which is why you mostly notice them during the autumn mating season when males abandon their webs to search for females. The spider sprinting across your living room floor is not looking for you. It is looking for another spider and is just as eager to be somewhere else.