Brazilian recluse spider bite
A brazilian recluse spider bite usually shows up as often painless at first, then a red mark that may develop a pale or blue-grey centre and, in some cases, an ulcer, red rim, dusky centre, appearing frequently unnoticed at the time. It peaks around pain and colour change over 24 to 72 hours and generally lasts weeks; a necrotic lesion can take months. Single site is the usual arrangement.
| Looks like | often painless at first, then a red mark that may develop a pale or blue-grey centre and, in some cases, an ulcer |
|---|---|
| Pattern | single site |
| Size | 5–80 mm |
| Appears | frequently unnoticed at the time |
| Worst at | pain and colour change over 24 to 72 hours |
| Lasts | weeks; a necrotic lesion can take months |
| Itch | ●●○○○ 2/5 |
| Pain | ●●●●○ 4/5 |
| Usually on | torso under clothing, thighs, upper arms — often bitten while dressing or in bed |
| Active | January to December, night |
How to tell it apart
Small, uniformly brown, with long thin legs and a violin-shaped mark behind the eyes. Bites happen when the spider is pressed against skin — while dressing, or turning over in bed. The bite is often painless, so the first sign is a mark that changes over the following days.
Where and when you meet it
Habitat: behind furniture, in wardrobes and among stored clothes and boxes — common in southern Brazil, particularly Paraná and Santa Catarina.
Where it is recorded
| Country | Records | Peak months there |
|---|---|---|
| Brazil | 208 | January, November |
Verified records from the GBIF biodiversity database across the seven countries we cover. A country missing from this table means we have no records for it, not that the species is absent.
What it means for you
Brazil records more Loxosceles bites than anywhere in the world, concentrated in the south. Most cause a local lesion that heals; a minority cause a systemic reaction with red blood cell breakdown, which is why dark urine and fever after a suspected bite are urgent rather than something to watch.
Seek medical care if
- a wound that darkens, blisters or breaks down over days
- fever, dark urine or yellowing of the eyes — these suggest the systemic form and need urgent care
- rapidly spreading redness and pain
Care at home
- wash, cold pack, elevate the limb
- seek medical assessment rather than treating a changing lesion at home — antivenom exists and is most useful early
- do not apply heat, and do not let the lesion be cut out early
Preventing the next one
- shake out clothes and bedding that have been stored
- move beds away from walls; avoid leaving clothes on the floor
- gloves when handling boxes and firewood
Common questions
How do I know it was a brazilian recluse spider?
Small, uniformly brown, with long thin legs and a violin-shaped mark behind the eyes. Bites happen when the spider is pressed against skin — while dressing, or turning over in bed. The bite is often painless, so the first sign is a mark that changes over the following days.
How long does a brazilian recluse spider bite last?
Typically weeks; a necrotic lesion can take months, peaking around pain and colour change over 24 to 72 hours.
When is it a problem?
Seek care for: a wound that darkens, blisters or breaks down over days; fever, dark urine or yellowing of the eyes — these suggest the systemic form and need urgent care; rapidly spreading redness and pain.
Can it transmit disease?
No human disease is known to be transmitted by this species in the United States. The practical risk is infection from scratching.
Get a photo assessment in the app
Everything above is free to read. The app adds what a page cannot: point your camera at the bite and get an assessment of the most likely cause, a severity read, and a day-by-day care plan — including the specific signs that mean you should be seen.
iPhone and iPad. Free to download.