Yellow Sac Spider bite

1/18/2015

There really aren't all that many spiders in the US that can do any damage to a human. The black widow and brown recluse get most of the press, and even with those, bites are fairly uncommon. But there is one spider that typically lives in houses, likes to nest in textiles like sheets and blankets, and can give a bite that is mildly nasty.

As a wildlife biologist, I have been bitten and stung by quite a number of things, from hundreds of bats of many species, to insects of all kinds, and even an ocelot. Sometimes it hurts a lot, and sometimes it just itches a lot, but such is what I do and I usually don't complain about such.

And I am not complaining now, just giving an introduction to a yellow sac spider bite.

The yellow sac spider (Cheiracanthium sp. probably mildei) is a spider found in many houses, that minds it's own business eating bugs that might make it into your house. Having spiders in your house is generally a good thing. But this spider has a toxic bite if you scrunch it while it is in the sheets. I have found and killed a couple at my current abode, but one got me.

Here is a photo of my little finger, between the knuckle and first joint.

yellow sac spider bite

This is the spider bite, between my knuckle and the first joint of the little finger on my right hand.

So what is going on here? First, the area puffed up like most bites/stings do from any insect. This is a reaction from my body's immune system and is normal, even though this is a bite from an arachnid not an insect. But there is more.

Arachnids, and in this specific case a yellow sac spider, can deliver different toxins and do some specific cell damage. Here, you are seeing the result of a cytotoxin, which liquifies cells. Yes, that is what is going on in the photo, the destruction of cells in my finger. Depending on how much venom was introduced, the damage will be such.

I have photographed this species of spider before, but no hope that I can find such this evening. So just the bite for now.

14 Comments

Sean

3/22/2017 10:38:23 pm

What happened to the yellow sac spider bite? Did it blister and how long did it take to heal?

Keith Christenson

3/22/2017 10:51:33 pm

Hi Sean, I wouldn't use the word "blister" for one of these bites, although from the photo that looks like what is going to happen. The bite turned an off color black/dark purple and more or less just slowly disappeared rather than falling off as a scab or blister might.

For each time I have been bitten by these spiders, the wound recovery time has been about 4 weeks until it is reasonably normal-looking, and some have left permanent round scars like you might expect.

Melissa Cruz

10/2/2017 08:26:30 am

I was bit by a yellow sac spider , I have many In my home , it started as what looked like a mosquito bite and quite itchy , it then turned into a very large swelled lesion and I actually had two swelled big lesions on my back , both a little bigger than the size of a quarter each and it was quite painful for the first 5 days , the best thing I used was cortisone 10 , 4 times a day - after day 8 I stared to notice it going down however it was then quite scabbed where the initial bite happened - it did not blister at all , but took about 3 weeks for it to go down to almost nothing , truly something I would never want again .

Robert DeWitt

5/19/2019 05:09:30 pm

Having spent a lot of time in the outdoors and growing up in the country we have always used home remedies to treats lots of ailments. My biological dad was a avid backpacker and paramedic which made me also follow along into emergency medicine. Our go to remedy for bites was always an adolfs meat tenderizer mud pack. The reason we would use adolfs was because its main ingredient was papain (papaya enzyme). My brothers leg was saved from a brown recluse bite because of this and the reason will follow. Adolfs was always in our first aid kits and used this treatment many times for our family and those we might be camping with. One day an off duty firefighter came to our quarters with his daughter that had a nasty bite asking the paramedic what to do. At the time i was just an EMT (but also a medic in the National Guard) and when I told him to get some adolfs and make a mud pack to treat his daughter they both blew me off. I was not happy about my advice being so quickly discarded so i did some research. I knew this treatment worked but did not know why. Most toxins from bites are made up of protein chains so when the papain reaches the toxins it begins to break up those chains (this is how meat tenderizer works) which then destroys their toxicity. Now adolfs has changed the recipe and now uses bromelain which i chose not to use out of a lack of knowledge of knowing its effectiveness. I purchased some papaya enzyme pills (a digestive aid) and grind them into a powder to make the mud pack. This powder does not make into a mud pack easily but does still work. My sister was recently bit by what might be a yellow sac spider or something else, without seeing what bit her we will never know, but the site started to become ulcerated. I applied a papaya enzyme mud pack which by the next day already had a huge reduction in the size of the affected area and of the pain which she was in. It is rare to find a medical professional who knows about this treatment although it was passed down from an ER doctor who also was an avid backpacker. I am not a doctor and this post should not be taken as medical advice but rather just retelling what my family has used. Always consult a doctor for medical advice.

Jenica Trifan

7/26/2021 09:44:30 pm

Thank you for the information Robert.

Derek Averell

8/27/2021 01:46:12 am

I used a digestive enzyme that had Protease SP as the first ingredient , and Bromelain as the 2nd. Made a little mudcake and applied it to my wifes face tonight after she got bit by a yellow sac spider. The mudcake worked nicely!! Thanks for the tip!

Dawn murphy

8/7/2019 01:57:39 pm

I had a bite on my small finger and it was just like this almost like a little blood bruised dot, it itched really bad, now it has a little hole

Keith Christenson

8/7/2019 03:55:32 pm

Hi Dawn, Yes, that sounds a lot like the bite from one of these critters. It'll heal up, but it does take some time and can leave a small scar that eventually fades as well.

Jan Martin McGuire link

9/9/2019 05:15:42 am

I live in Tanzania. I was bitten by what I think is sac spider bite. Usually called a Long Legged Sac Spider - Cheiracanthium. I had what I would term a blister that looked a lot like yours. The doctor at the hospital drained it - there was only fluid and blood, no pus, but it was early on. I saw the blister in the morning, which was painful, but we thought maybe a burn as we light our stoves with matches and sometimes flecks of it snap off and fly and can burn. I put antibiotic ointment on and a bandaid. Later in the day when I checked it had a red ring starting around it. Put another bandaid on. Then later thought I remembered you shouldn't cover burns, checked on the internet, saw that it said not to, so took it off that's when I saw it had turned red/purple and we went to the doctor.

Some debate here if sac spiders bites are harmless or not. Without seeing the spider I can't say for certain but it sounds like it. I had reached up and pulled down our mosquito netting to repair it and assume it had a "sac" cover there. My finger started hurting quickly but the blister formed also. Anyway. Just my experience.

Desiree

1/9/2021 01:06:37 am

The picture above looks like a bite i have on my pointer finger right now. i have 2 different looking sores on the same finger which are about a 1/4 of inch or less apart from each other and they are both painful. Do yellow sack spiders usually bite more than once. Im assuming its a yellow sac spider because of the picture and description of others experiences. It also looks very similar to another bite on got on my foot about 6 months ago. Plus i have killed several yellow sac spiders in my house. One other question do yellow sac spider like to leave in stacked papers? I was going through paperwork in my house and i did kill one yellow sac spider that came out but i know i wasnt bite at that time. Im just thonking when i messed with the paperwork i may have flushed more than out. Thank for any information u maybe able provide.

Keith

1/10/2021 10:37:18 am

It is my experience that getting two bites somewhat close together does happen on occasion. It has happened to me once as well. The usual time when one will get bitten is when the spider is in some type of linen, like a couch blanket or even clothes, and when you wrap that around you or put it on the spider gets squeezed and may bite. Just finding one living in a dark crevice, like between some papers, is very unlikely to cause any bites.

Jennifer

3/27/2022 08:21:04 pm

Damnit. I think my geriatric dog was bitten by one of these. He feels miserable. But the wound is doing exactly as described. Red, swollen, hard, then started turning purple, bled for a hot second, now the middle is black and starting the collapse and the hardened swelling is a little bigger than a quarter after starting as a little smaller than a dime. He feels miserable. Isn't eating, can hardly walk, panting, can't get comfortable, etc etc. I'm so bummed that I'm reading 3 or 4 weeks for healing!!

Zoe link

7/4/2022 07:30:03 am

Thanks for sharing this useful information! Hope that you will continue with the kind of stuff you are doing.

Jen

4/20/2023 02:39:41 pm

Thanks for the photo and description. I suspected that this is what had happened as I routinely have to go through my old farm house and clear these guys out. Nice to have it confirmed. My finger looks almost exactly like this photo with a bit more swelling and a hole in the middle. And it hurts/itches too. Ah, well. Nature.

Yellow Sac Spider bite

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