False widow spider bites
How dangerous is a false widow spider bite?
False widow spider bites are uncommon, and most documented bites from the noble false widow (Steatoda nobilis) have caused mild to moderate local symptoms such as pain, redness and swelling. However, more significant reactions have been documented and some confirmed cases have required medical treatment or hospitalisation.
The best clinical evidence comes from confirmed Steatoda nobilis bites in which the offending spider was collected and identified. An Irish and British case series published in 2018 reported immediate pain, redness and swelling in all five cases studied, with symptoms resolving within 48–72 hours and no further complications. A larger case series subsequently documented a wider range of effects, including severe pain, tremors, fatigue, nausea, low blood pressure and impaired mobility in some patients.
False widows are not considered aggressive towards people. Bites are most likely to occur when a spider becomes trapped against the skin, caught inside clothing or bedding, or accidentally disturbed at close quarters.
“Symptoms ranged from mild to severe, requiring hospitalisation in some cases.”
— Dunbar et al., University of Galway, Clinical Toxicology
How does false widow venom compare with black widow venom?
This helps explain why some confirmed noble false widow bites have produced Latrodectus-like symptoms, including severe pain, tremors and nausea. However, similarities in venom composition do not mean that false widow and black widow bites are equally dangerous to humans. Clinical outcomes from noble false widow bites are generally milder, although significant reactions can occur.
Black widow spider – Latrodectus
What does a false widow spider bite look like?
There is no unique appearance that can reliably identify a false widow bite from the skin alone. Redness, swelling and tenderness around the bite site are among the most commonly documented local effects, but these can also occur after many other insect bites, stings, skin irritations and infections.
A confirmed false widow bite may initially produce a painful, reddened or swollen area. Some documented cases have also involved itching, blistering or more extensive inflammation, but these are not features that occur in every bite.
This is particularly important when looking at photographs online. A severe blistered or infected skin lesion should not automatically be attributed to a false widow spider simply because one has been seen nearby. Reliable confirmation is much stronger when the bite itself was witnessed and the spider responsible was collected and professionally identified.
Rare skin lesions interpreted as tissue necrosis have been reported following confirmed noble false widow bites, although the role of the venom in producing necrosis has been debated in the clinical literature. Secondary skin infections, including cellulitis and dermatitis, have also been reported.
False widow spider bite symptoms
Symptoms following a false widow bite vary considerably between people and between individual bites. Most reported reactions are localised around the bite site, while systemic symptoms affecting other parts of the body have been documented less commonly.
Common local symptoms
Reported local symptoms include:
- Pain or tenderness
- Redness
- Swelling
- Itching
- Localised warmth or inflammation
The 2018 Irish and British case series found immediate sharp pain together with varying degrees of redness and swelling in all five confirmed cases.
Less common systemic symptoms
Reported systemic symptoms include:
- Severe or debilitating pain
- Tremors
- Fatigue
- Nausea or vomiting
- Dizziness
- Low blood pressure
- Reduced mobility of the affected limb
More significant envenomation can produce symptoms beyond the immediate bite site. Confirmed noble false widow cases have included debilitating pain, tremors, fatigue, nausea, vomiting, dizziness, low blood pressure and impaired mobility of the affected limb.
These symptoms are not typical of every false widow bite and should not be interpreted as the expected outcome.
More serious complications
- Blistering
- Significant or spreading inflammation
- Cellulitis
- Dermatitis
- Secondary bacterial infection
- Rare reports of skin lesions interpreted as tissue necrosis
Blistering and significant local inflammation have been reported in some cases. Cellulitis, dermatitis and other bacterial infections have also been documented following bites.
Rare skin lesions have been reported following suspected or confirmed noble false widow bites, including cases interpreted by some researchers as tissue necrosis. However, whether the spider’s venom directly causes necrosis remains debated in the clinical literature.
Severe symptoms requiring hospital treatment have occurred in the published case literature, but they represent the more serious end of a spectrum in which many bites produce considerably milder effects.
How do false widow bite symptoms develop?
There is no single set of “stages” that every false widow bite follows. The timing and severity of symptoms vary, so diagrams online showing a fixed progression from a small mark through blistering or tissue damage can be misleading.
Pain can begin soon after a genuine envenomation. Redness and swelling may then develop around the bite site, while itching or other local symptoms can appear as the reaction progresses.
In the five confirmed Irish and British cases published in 2018, symptoms subsided within 48–72 hours. Later research documented some more severe cases with longer-lasting complications, including bacterial infection and skin inflammation.
For this reason, it is more useful to monitor whether symptoms are improving or worsening than to expect a bite to pass through a particular sequence of stages.
For the scientific research and medical sources used to support information on this website, see our research and sources.
How to treat a false widow spider bite
The majority of reported bites from a false widow are mostly mild and no fatal bites have been documented.
1
Clean the wound by washing the area with soap and water
Apply a cloth cooled with water or an ice pack for at least 20 minutes
Avoid infection by covering and not scratching the wound
Seek medical advice if:
- pain or swelling becomes severe or continues worsening
- you develop vomiting, dizziness or significant systemic symptoms
- the wound appears infected
- symptoms are persistent or worrying
The National Poisons Information Centre (NPIC)
Contact the NPIC, a GP or pharmacist if pain persists or swelling develops.
How to avoid a false widow bite
False widow spiders are not aggressive towards people, and bites are most likely to occur when a spider is accidentally trapped against the skin or disturbed at close quarters.
Check clothing and bedding
Cover frequently opened windows
If spiders regularly appear around windows you leave open, a window screen can place a physical barrier across the opening while still allowing ventilation.
Wear gloves when appropriate
Wear gloves when clearing sheds, moving stored materials or working in places where spiders may be concealed. Store gloves somewhere spiders cannot easily enter them.
Check bins and outdoor containers
False widows can build webs around sheltered outdoor objects. Check handles and areas where you place your hands before moving wheelie bins, storage boxes or similar containers.
Reduce webs in problem areas
Regularly removing webs from places where you don't want spiders can make those areas less suitable for them and reduces the chance of accidentally disturbing a concealed spider.
Take care when moving stored items
Boxes, garden furniture and other objects left undisturbed for long periods can provide sheltered places for spiders. Check before reaching underneath or behind them.
See our practical guide to keeping spiders out of your house throughout the year.
What if you regularly find false widows indoors?
That can include screening frequently opened windows, sealing obvious gaps, reducing clutter in undisturbed areas and removing webs where spiders are repeatedly establishing themselves.
For a broader look at these measures, see our guide on how to keep spiders out of your home.
False widow spider species in Ireland
The three most common false widow spiders in Ireland and Britain are Steatoda nobilis, Steatoda grossa, and Steatoda bipunctata.
Noble false widow spider
Steatoda nobilis
Cupboard spider
Steatoda grossa
Rabbit hutch spider
Steatoda bipunctata
False widow spider in Ireland stories
Cupboard spiders get a gentle hooshing
Look what I found cleaning out my bird seed storage a while back… One of the False Widow species… A first for me! The cupboard spider – Steatoda grossa. About 3 or 4 of them. Was surprised to find so many large spiders tolerating each other in the small confines of a garden seat box used to store bird feed.
Met my first false widow today!
This morning, a fresh sunny day in April in coastal Galway, just as we were getting the kids ready to leave for school, a false widow spider started making its way from the front door across our hallway. It wasn't moving too quickly so I was able to get an envelope to put under it and then take it outside. Once outside, I immediately noticed it shot...
False widow spider in my pajamas!
A Close Encounter in Cork Hey there! Hope you're keeping well, I actually stumbled across my first false widow spider earlier today and identified it with the help of the internet. I have nothing but good things to say about it honestly! I typically tend to keep my pajamas on if I know I'm not going out for the day, so I had them on for quite a while. I...
False widow spider in my house
Over the past year I have noticed a lot of false widow spider webs in my back garden around my shed. I recognised them due to their messy box/sail like shape - as opposed to the traditional neat patterned web of a typical garden spider. The spiders are only active at night so I wasn't too concerned. But I was very surprised by how many of their webs...
Baby false widow spider bite?
Was it a baby false widow spider bite? I'm pretty sure I sustained a baby false widow spider bite this summer but I'm not 100% sure. I have seen loads of the adults recently, really for the first time too. A neighbour told me last year that they had a lot of false widow spiders in their back garden. That year I started to notice a few around the outside...