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Spider Envenomation in Dogs
Written By hannah hollinger
Published: 06/16/2016Updated: 06/03/2021
Veterinary reviewed by Michele K.
What is Spider Envenomation?
Most of the spiders in the United States do not have severely painful bites, and only a few of the spiders in the United States are venomous to the point of the dog requiring serious medical attention and possible hospitalization. Usually when a spider bite occurs, the spider doesn’t stay around and it is hard to identify whether that is the problem the dog is having.
Even though many of the spiders are relatively harmless or may only require a small amount of medical attention, there are a few venomous ones. These include spiders from the widow group, and the most common spider from this group is black widow spider. Another venomous spider comes from a brown spider group called the brown recluse spider. Tarantulas are known to be relatively harmless to humans even though their bite is quite painful; however, dogs are more susceptible to tarantula venom than humans and immediate medical attention is required. Black widows, brown recluse, and tarantula bites can be very serious if they are not treated in a timely manner or at all. All three of these spiders can cause death if the dog is not taken to the veterinarian and properly treated.
Spider envenomation  in dogs occurs when a spider, possessing toxic venom, inflicts a bite upon a dog. The toxin from the venom causes severe inflammation that requires immediate medical attention.
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Symptoms of Spider Envenomation in Dogs
When a dog becomes a victim of a venomous spider, the signs will vary, depending on the dog. Signs include:
  • Trouble breathing
  • Arrhythmia
  • Pain at the site of the bite
  • Muscle stiffness
  • Paralysis
  • Abdominal stiffness
  • Abdominal tenderness
  • Anxiety
  • Restlessness
  • Rapid and shallow breathing
  • Muscle cramps
  • Lesion at the site of the bite
  • Red ring around the bite area
  • Fever
  • Vomiting 
  • Seizures
  • Joint pain
Types
It may be difficult to witness the actual spider bite, and oftentimes the type of spider that has bitten the dog may be unknown. Types of spiders that are venomous to dogs include:
  • Brown recluse
  • Black widow
  • Red widow
  • Brown widow
  • Wolf spider
  • Brazilian wandering spider
  • Yellow sac spider
Causes of Spider Envenomation in Dogs
The cause of spider envenomation in dogs is the injection of toxic venom into a dog by biting. There are many species of spiders, and the different species have a different level of toxin in the venom. The spider bite is toxic because:
  • The fangs penetrate the skin and inject venom from the holes in the fangs
  • The venom is projected through ducts inside the fangs, which lead to the venom glands
  • Neurotoxin enters the dog’s bloodstream and can lead to the harmful symptoms, including paralysis and sometimes death
Diagnosis of Spider Envenomation in Dogs
If your dog is showing any signs of a spider bite, it is important to take him to the veterinarian immediately. The veterinarian will ask you questions pertaining to the spider bite, such as if you witnessed the spider around the dog. More than likely the signs will occur after the bite, and unfortunately it is common to not see the spider that bit the dog. The veterinarian will perform tests and then rely on the dog’s clinical signs to make the diagnosis.
The veterinarian may perform a biochemistry profile (to check organ function), blood work, test for electrolytes, and urinalysis. While these tests do take time to come back and possibly show any toxic effects, the veterinarian must go ahead and treat the dog according to the signs, including the site and area around the bite.
Treatment of Spider Envenomation in Dogs
To treat a spider bite, the methods may vary depending on the type of spider that bit your dog. For example, if a brown recluse spider bit the dog there will be other methods of treatment since the spider is highly venomous. 
The treatment for your dog’s spider bite will depend on the severity, how the dog is reacting to the bite, and the type of spider.
Cleansing
The first thing the veterinarian will do is thoroughly cleanse the affected area around the bite.
Pain Medication
Pain medication will be given. Corticosteroids can also protect against further impact upon the system. Muscle relaxants or morphine may be given to help with the pain.
Antibiotics
In order to prevent a serious infection, especially in cases of brown recluse spider bites, antibiotics may be given. Anti-venom may be given for bites from black widows. Also, tetanus antitoxin is often given especially if the dog has never had a tetanus shot.
Oxygen Therapy
Oxygen therapy may be given to help the dog breathe in cases of severe spider bites.
Fluids
Along with the above methods of treatment, the veterinarian may administer fluids to the dog through an IV. This will help keep the dog hydrated, and along with the oxygen therapy, will help keep his blood pressure down.
Antivenin
The type of spider that has bitten your dog will determine if there is an antivenin to help treat the spider bite, for example, there is an antivenin for black widow spider bites.

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Recovery of Spider Envenomation in Dogs
In terms of recovery and management for spider bite envenomation, it depends on the type of spider that inflicted a bite upon your dog. It also depends on the severity of his condition. If the dog was able to get to a veterinarian after the bite within a timely manner, prognosis is good. Once your dog comes home after treatment, it is important to keep checking the site of the bite for any changes in to alert the veterinarian if new signs or behavioral changes occur. The veterinarian will give instructions on how to properly care for your dog after treatment, and may request a follow-up appointment to check on his healing.
Spider Envenomation Average Cost
From 38 quotes ranging from $300 - $5,000
Average Cost
$1,000
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Spider Envenomation Questions and Advice from Veterinary Professionals
Pit Bull
Eleven Years

6 found this helpful

6 found this helpful

My pet has the following symptoms:
Vomiting
Good afternoon, Yesterday I spent the afternoon at my moms house in the backyard. My dog Nala was hanging around I noticed her eating grass a few times but caught her before she ate a lot of it (this is not abnormal for her) this morning when we woke up she had thrown up multiple times and one side of her face was very swollen under her eye and lips. Throughout the day she has continued vomiting and hasn’t had an appetite. I’m not sure what could have made her so sick. Could this be a spider or snake bite? I don’t see any abnormal spot on her other than a few areas of redness on her mouth
Oct. 25, 2020
Answered by Dr. Linda S. MVB MRCVS
6 Recommendations
Thank you for your question. Her symptoms of facial swelling and vomiting are a concern. Possibilities would include a bite or sting, allergic reaction, abscess etc. It is important she is checked over by a vet and she likely needs some medicine, which may include anti-inflammatories and antibiotics.
Oct. 25, 2020
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Pitbull Lab mix
One Year

0 found this helpful

0 found this helpful

My pet has the following symptoms:
Redness In Eyes
My dog has red eyes and looks like a spider bite on her neck area. Keeps scratching her face. I brushed through her hair but am worried the spider bight might kill her is there anything I can do to help since vets are closed. I’m in Mexico ciudad Juarez.
Sept. 26, 2020
Answered by Dr. Michele K. DVM
0 Recommendations
Thank you for your question. I hope that she is okay. If she is still having problems, It would be best to have your pet seen by a veterinarian, as they can examine them, see what might be going on, and get treatment for them.
Oct. 14, 2020
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Dachshund
One Year

0 found this helpful

0 found this helpful

My pet has the following symptoms:
Can’T Walk With Back Legs
He was fine all day. Wednesday I gave him a dewormer and this afternoon he is having trouble walking with his back legs. He continues to have diarrhea
Sept. 26, 2020
Answered by Dr. Michele K. DVM
0 Recommendations
Thank you for your question. I apologize for the delay, this venue is not set up for urgent emails. I do no think that what you are describing is likely due to the dewormer, unless the dose that he got was way too much for him. Since I cannot see him, It would be best to have your pet seen by a veterinarian, as they can examine them, see what might be going on, and get treatment for them.
Oct. 19, 2020
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Chihuahua
Five Years

1 found this helpful

1 found this helpful

My pet has the following symptoms:
None
Was wondering.... if my small deerhead chihuahua is very sensitive to most any pain, and if I was fairly close to her while she was most likely in danger or likeliest exposed, is it probable that I would've noticed her reaction if she had been bitten by a large black widow spider? I mean to ask is a black widow's bite even painful enough for her to yelp or bark or give her ANY reaction at all at the moment the spider would have bitten her- perhaps on her paw or muzzle?
July 30, 2020
Answered by Dr. Sara O. DVM
1 Recommendations
Hello, Dogs should not take human pain medication as just a small dosage can kill them. It would be best for you to get pain medication from your vet. A spider bite can cause your dog to be painful and should see your vet. There are also many other reasons that would cause your dog to yelp in pain. Your vet would be able to examine your dog and figure out what is going on with him as well as getting you pain medication. Good Luck.
July 30, 2020
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German Shepherd
6 months

4 found this helpful

4 found this helpful

My pet has the following symptoms:
Swelling, Pus,
I believe my dog possibly got bit by a spider but I'm very unsure. she stopped eating for a couple of days and I've been giving her Pedialyte and antibiotics I had some amoxicillin so that's what I've been giving her. After 7 days she's now back to her silly self and is eating a lot better and also drinking. but her foot where it looks like she has gotten bent the swelling has finally gone down but it's still very dark colored and has some spots that look like pus blisters(?). I did clean the wound with iodine and I wrapped it up even though she's not really wanting to keep it on I still have a few antibiotics left that I'm trying to give herwhat could I do
July 24, 2020
Answered by Dr. Michele K. DVM
4 Recommendations
Thank you for your question. The only other thing that might need to happen for her would be stronger antibiotics. Those you can get from your veterinarian, and it may be a good idea to have an examination for her given the level of trauma that she has gone through. I hope that everything goes well for her.
July 24, 2020
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Pit bull
booger
4 Months

0 found this helpful

0 found this helpful

My pet has the following symptoms:
Hives
Swollen Face
Occasional Raspy Breaths
Very Mild Vomiting
i'm not entirely sure what brought this, i'm assuming a spider bite since they're so plentiful in my home.. booger is acting normal, maybe slightly lethargic but he's an abnormally lazy puppy so it's hard to tell. he had moderate to severe hives for a very short period of time, mainly on his lower belly, maybe lasted ten or fifteen minutes, then they subsided but have come back worse again in different places, specifically the armpits & the lower part of his belly. he wasn't very interested in drinking any water. he had rapid hiccups, or what i would assume them to be, for a few brief seconds & then vomited very small amounts of a light yellow foamy liquid, three or four times back to back. acts totally normal, doesn't seem to be in any pain whatsoever, still walking around, even running after me wagging his tail. breathing is fine until he lays a certain way, then it's almost like he's a little congested.. going to buy some Benadryl for now, he doesn't have any discoloring of the gums they look pink & normal so breathing is still good, airways open. i can't find a bite, would it be possible that the spot he were bit would be painless? i've rubbed my hands all over his body, pressed gently over it again with my fingers, & then again with more force. he showed no signs of any tender places or pain. is this normal for hives to do, come & go with various severities? i think if he were to become fatally ill, it would have either happened by now or his condition would have worsened. any ideas what this could be, if not a spider bite? should i be concerned if he doesn't show signs of the symptoms getting worse? right now he is asleep, dreaming like he usually does. he has yet to act any different.
Mixed breed
Bear
7 Years

1 found this helpful

1 found this helpful

My pet has the following symptoms:
Weak Back Leg
Hi there. My dog was fine and playing this afterboon as usual. Now he is struggling to walk and get up. At first I though he might have hurt a muscle in his back leg, but now i am getting more worries, and probably more paranoid, that a spider but him. We have black & brown widows in our area and brown recluse. I have not seen any, but i know they are probably lurking somewherin the garden. He still has a great appetite and is standing up to go do huis number 1 outside, however he really struggles to get up. Can a spider bite kill him overnight? We do not have any vets available nearby on a Sunday evening. Im just really worried.
Great Pyrenees
wrangler
1 Year

0 found this helpful

0 found this helpful

My pet has the following symptoms:
Unsure
my puppy was running around the house shaking his head roughly, when i came up to him i found a very large common black house spider. he killed it but I'm very unsure if the spider bit him... i couldn't see anything right away on his nose or lips, but then again i don't know how long it takes for the symptoms to kick in. he has black and white speckled lips, nose, and gums because of his breed mixing
Spider Envenomation Average Cost
From 38 quotes ranging from $300 - $5,000
Average Cost
$1,000

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