How to Identify a Spider Bite

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How to Identify a Spider by Its Bite

A black widow spider, with its tell-tale red hourglass. If you feel pain when the spider bites, this is likely the culprit.

by James Hubbard, MD, MPH

I’ve seen a lot of spider bites in my day, and more often than not, the spider is never seen. Over the years I’ve developed several tricks for how to identify the spider by the bite.

There are three types of poisonous spiders in the U.S. The brown recluse is found in the southern two-thirds of the country. It likes to hide in boxes so I often wonder if it doesn’t catch an occasional ride by freight. The hobo spider likes it out west. The black widow has been found in every state but Alaska.

Here are my tips on how to identify a spider bite.

1. Evaluate the Pain

If you feel pain when the spider bites, it’s likely a black widow, whose bite is often but not always painful. You may also develop severe body aches and fever.

A brown recluse spider bite is a slight sting at best. Most of the time you feel nothing. They hide in or under boxes, under your bed sheets, in your clothes. The first you know about it is the pain that develops several minutes to hours after the bite.

A brown recluse spider bite, two months later. This is the eschar—the black, leathery, dead tissue—that can form over the wound. The photographer writes that it was surgically removed about a month after this photo.

A hobo spider’s bite feels similar to a brown recluse’s, and the pain also occurs minutes to hours after the bite.

2. Look at the Skin Damage

That’s the key to the brown recluse spider bite. You may not know when it bit you, but the bite area becomes red, blistered, or black. The area starts out small, and the redness spreads. A black spot of dead tissue develops in the middle of the redness. This dead tissue can be anything from small and superficial to deep and large—sometimes enough to warrant a skin graft when everything’s said and done. As the tissue dies, the area becomes very painful.

The hobo spider can cause skin damage, but less so than the brown recluse.

The black widow spider bite causes a red spot that’s sometimes hard to see. (More obvious: It can cause plenty of muscle aches and cramping throughout the body for one to three weeks.)

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How to Treat a Bite From a Poisonous Spider

If you can get to a doctor, do so. If you can’t, consider the following.

If you think the spider was a brown recluse or hobo:
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  1. Slow the venom’s spread: Apply ice, and keep the area at heart level or above.
  2. Prevent infection. As the black layer of dead skin (eschar) sloughs off, treat the wound as you would any other, by keeping it clean and covered and applying antibiotic ointment or honey. Some large wounds take several weeks to heal. If it starts looking infected, you’ll need oral antibiotics.
  3. Treat the pain. Take an over-the-counter pain reliever.

Some think steroids might decrease the extent of skin damage from a brown recluse bite. Sometimes skin grafts are required when the wounds are too big to heal on their own.

If you think the spider was a black widow take a pain reliever like ibuprofen or acetaminophen for the muscle cramps.

Within minutes to hours, a black widow bite can lead to severe chest and abdominal pain mimicking appendicitis or a heart attack. It can make your blood pressure go up, which may need to be treated. (Possible signs include an increased heart rate and a flushed face.) If you can’t get to a doctor, rest to try to lower the blood pressure. In worst cases, antivenin may be given.

The good news is it’s very rare to die from a spider bite.

Has anyone ever had a brown recluse, hobo, or black widow bite? How did you identify the spider type? What were the symptoms? How was it treated? How are you doing now?

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Black widow photo by Texas AgriLife Extension Service. Photo of brown recluse spider bite by Jeffrey Rowland.

  • chili

    I got bit by a spider two days ago. It was a stinging pain and I thought it was just a splinter – I was at a playground with wood chips all over. So I brushed myself off and felt a bug come off my arm. I didn’t think it was a spider at the time because I didn’t see it. When i got home I could see the two red fang marks on my elbow. The red swollen area spread to about apricot size. As soon as I suspected a spider bite, i washed it and made a paste of White vinegar and Baking soda and kept applying that through the next day. When I woke up the next day, I felt tired and my muscles were stiff like I had worked out the day previous. The fang marks were raised up and filled with yellow pus which popped when I put the baking soda and vinegar on. I didn’t think anything about that, but kept applying the baking soda and vinegar paste and took benedryl. I slept all afternoon of that day. When I got up the third day I was still so exhausted for some reason. I had to go to work, so I put neosporin on the bite mark and went to work. All day I felt so tired and exhausted. Maybe from the benedryl but I haven’t ruled out the spider bite just yet. The redness has gone down to a more localized area around the fang marks probably about a quarter size. I haven’t felt any other symptoms other than feeling drained and utterly exhausted. The spider bite is still itchy and the fang marks can still be seen but there is no sign of skin decay. Hopefully the exhaustion will wear off in a couple days as the bite heals.The pictures from left to right are Day 1, Day 2, and Day 3

    • James Hubbard, MD, MPH

      Wish you the best. If you continue to have symptoms, have them checked out.

  • Bethany Rucker

    Woke up with these irritations on my arm and abdomen, they are red, warm and slightly hard. The one on my arm seems to have a line going up my arm along my vein, I’m very concerned. I’m going to see a doctor after work, but I’d like to have your opinion, please and thank you.

    • James Hubbard, MD, MPH

      Sounds like cellulitis. Please let me know what your doctor says.

  • Reagan :)

    In September of last year I was doing my homework in my room and I fell asleep. It was about 15 minutes later when I woke up itching and in pain. When I first saw the bite it looked like a pimple on my leg and I didn’t really worry about it but, just in case. I circled the dot. About 24 hours later I noticed that the red had spread way past my circle! I showed my mom right away and she took me to the hospital. We waited for hours and the pain was unbearable. I had fatigue, I was having cold sweats, and body pain like crazy. I told the doctor that I didn’t see or capture the spider and he said that it was definitely a poisonous spider. The doctor told me that if I would have waited even just a day longer they would have had to cut my leg open! They gave me antibiotics to take twice a day for a week. It’s now not even a year later and I still have the scar. The pain has gone away and I’m doing much better now (with a case of arachnophobia lol)! It was such a scary thing for me. If you get bit by a spider it’s best to go straight to the hospital, it’s better to be safe rather than sorry!

    • James Hubbard, MD, MPH

      Thanks for sharing

      • Reagan :)

        No problem! Thank you so much for making this blog! I hope my story helps others!!

  • EWright

    My gf and I went camping for the 4th of July weekend. the night of the 4th she began complaining about this spot on her leg which started out as a small raised bump with some redness. By Sunday night it began getting deeper and bigger. Tuesday she went to work and put band aids over it because of the pain against her clothes and when she got home and pulled off the band aids all the skin around it started coming off with it. I know you cannot diagnose what this is but to me I am worried about it being a spider bite and it is getting worse and worse. Her pain is pretty bad as well. Anyone have any idea what this looks like, or what it could be?

    • James Hubbard, MD, MPH

      Could be a spider or any insect. If it’s getting worse it needs to be checked by a doctor. If infection is the cause antibiotics may be needed.

  • Lisa Nelson

    I don’t know what I got bitten by because I did not see it, however it has itched all day. The picture does not show that well, but there are 2 marks close together, both are raised, and have like little dark spots in the middle. Keep in mind these are very small marks. Should I be concerned? I am not running a fever, but the area around the 2 marks is red.

    • James Hubbard, MD, MPH

      Well, I’m getting around to this a little late. How is it doing now?
      It could have been virtually any insect or spider that caused a local reaction. If that were the case, it should be gone by now.

  • briannaah

    I have a spider bite from 3 days ago , I saw the spider on my but I didn’t think it was a spider , so I left it there …. I saw it was gone 5 minuets later but also when it left I felt the sting , the sting was just barely anything but it itched and itched and itched , but its real puffy and it bleeds alot , and when I take a shower it burns like crazy!! My mom said I’m gonna have to get it lanced but I don’t even know why?!?!? It’s puffy like a centimeter high , but it only itches when I change clothes and when I take a shower , any help?

  • Christine

    Do these resemble spider bites?

    • James Hubbard, MD, MPH

      Christine, sorry, but I don’t try to specifically diagnose without a direct exam. It would nice to know what bit you so you’d know, for instance, if you had something in the house to get rid of but, in general, the bottom line with any bite is what kind of reaction it is causing. If none, such has whelps, infection, fever, skin loss, then keep the area clean. Again, that’s a general statement. If you have specific concerns, have it checked.

  • Brandy Wright

    I was bitten by something two days ago. I never saw it but I was down working in the lawn and it got in my jeans. I didn’t feel the initial bite but for nearly two hours after all I feel was pins and needles or almost like a bunch of bees stinging at once.. even like things crawling on me. It turned red in about a three to four inch circle quickly.. two days later its turning dark in spots. Still burning and hot but the pins and needles effect left. Its very sensitive and the top layer of skin seems to be peeling. Any idea what kind of bite this might be? Tomorrow is day three and it went fromred to turning dark. I know you can’t diagnose but any suggestions? Its not wanting to allow me to upload the photo..

    • James Hubbard, MD, MPH

      Just speculating, it sounds like it could have been a brown recluse. If that were the case, it had to have been in your jeans before you put them on or in a pile of debris. If not, many insects can give you a pretty bad local reaction. If the reaction is bad enough, it could kill some top layers of skin which would slough off. But, as far as I know, only a brown recluse is going to kill deep tissue. If it’s getting worse, you should see a doctor.

  • Teila Smith

    ive been noticing a lot of tiny little spiders around my house lately. never really looked too close at them. somebody thought it would be a good idea to bite me though. i have several tiny little blisters on my inner arm now. although i highly doubt its a brown recluse bite even though they are common here i am putting a mixture of bentonite clay, powdered plantain leaf (the broadleaf herb not the fruit), and powdered echinacea. i hope one day modern medicine institutions will realise and appreciate that sometimes when modern medicine lacks or fails, natural remedies really can be effective (they already do with honey in burn wards). besides i used this treatment on my boyfriend last year when he actually was bit by a recluse and you wouldnt even know it by looking (no necrosis or infection, apparently it stung quite a bit until the clay pulled all the poison out) took several days of treatment (change poultice 3-4x daily) but its better than a shot in the rear of overpriced ER antibiotic and steroids (activated charcoal (only effective the first several hours after the bite), bentonite clay powder, powdered plantain leaf, powdered echinacea a. and p. all cost about $15 from the herb store). youll also want to make tea with the echinacea and drink it about 3 times/day. it acts as an antibiotic and stops secondary infection which is common especially in recluse bites. the other items pull out the toxins and the plantain soothes. the plantain can also be mixed with the echinacea powder to make tea. treat it from both sides. 1/2 teaspoon of each to a cup of boiled water steeped tightly for 10 mins. vit C is also a good idea. as with all herbs please check for contraindications with health issues you may have or pharmaceutical drugs you may take. i would imagine aside from the bentonite clay these herbs could be interchanged with garlic/black elderberry/ tea tree oil (do not take internally) for infection and calendula/lavender/tea tree oil for irritation or any number of other herbs that give the same benefit without risk of allergy/interaction. hope this makes sense and helps

  • Brendette

    let the air bust and dry the wound DONT do it yourself