A Spider Bit Your Dog: Identifying the Bite & What You Should Do

Most spider stings on your dog will result in swelling and redness that won’t require veterinary attention. There are, however, a handful of spider species whose bites may be deadly to dogs. Spiders are highly dangerous, so in this post, we’ll consider how to recognise that a spider has bitten your dog and what to expect during your appointment with a veterinarian.

Which Spiders Are Considered Dangerous?

A few spider species originate from the U.S. Out of these, there are two major venomous species to be cautious of:


  • Brown Recluse: The brown recluse spider, Loxosceles reclusa, is the most common poisonous spider that stings your dogs. They have a violin-shaped design on their bodies and are active at night.


Recluse spiders bite your dog most often when they are sleeping. They are often found in closets, dry basements, and attics. These spiders are usually found in the Midwest, although they can also be found in some parts of Southern California, Western Arizona, and New Mexico.


  • Black Widow: The sleek black bodies of black widow spiders are distinguished by an orange or red hourglass spot on their underbelly.


The offspring of these spiders are usually brown with orange or red marks that fade into an hourglass shape as they mature. Black widow spiders can be found in every state in the U.S., excluding Alaska. They love to dwell around buildings. The female ones are the only poisonous ones.

Identifying a Spider Bite on a Dog

Spider bites can vary in severity based on the spider. Brown recluse spiders, for instance, have a poison that produces a localised cutaneous backlash in humans. 


Although there is no agreement on how these bites appear on your dogs, clinical indications in humans are:


  • Itching and soreness occur first, followed by pain on the bite.
  • The appearance of the target lesion is a darkened region of skin that has lost blood supply and hence turns red.
  • Nausea, fever, joint pain, or rash.
  • The dark region normally blisters and hence falls off 1–5 weeks after the first bite, leaving a deep wound that’s hard to heal. The amount of poison injected determines the degree of harm.
  • Brown recluse stings may cause anemia and kidney diseases in some people.


Black widow spiders, however, have a poison that contains a potent neurotoxin called alpha-latrotoxin. However, according to the 6th version of The Five-Minute Consultation Veterinary, 15% of black widow stings are venom-free and cause no symptoms other than redness of the affected area.


If the envenomation is mild, symptoms may not appear for weeks. If a black widow has poisoned your dog, clinical signs include:


  • Tremors and cramping
  • Cramping and tremors
  • Restless 
  • Hard belly
  • Pain 
  • Fast heartbeat
  • Salivating 

What Should I Do If There’s a Spider Bite on My Dog?

Contact your veterinarian if you suspect a spider has bitten your dog. If your dog shows clinical signs, contact your vet to book an appointment. If your vet can’t see you, you may be referred to the nearest emergency hospital. Carefully transport the spider inside a container if possible.


Apply an ice cube to your dog’s bite wound. Remember that your dog can bite in pain or fear. Use these Fear Free Happy Homes guidelines to learn how to deal with your dog when frightened or in pain. Breathe and keep calm while caring for your dog.


You can administer an antihistamine, such as Benadryl, orally before leaving the house only when your vet suggests it. Inquire with your veterinarian about the proper dosage.

What Will Happen at the Vet?

Your veterinarian will take your dog’s vitals and perform a comprehensive physical examination. If available, give them all the required information, including the spider that bit your dog. Laboratory hospitalisation and testing may be necessary based on the spider species involved.


If your veterinarian suspects a brown recluse has attacked your dog, there isn’t much you can do at first. The bites of such spiders usually take a prolonged period of 4–6 months to heal.


While you perform the majority of the treatment back home, keep the wound clean at all times, and keep in touch with your veterinarian, even if it’s simply for weekly calls. If a deep ulcer develops, antibiotics will most likely be prescribed to prevent secondary bacterial contamination. Your vet may also prescribe pain relief medications if your dog is in pain.


If the wound enlarges and develops a dead region in the centre, your veterinarian will likely propose amputation of the unfunctional tissue. Your vet may also recommend a skin graft to aid in healing your dog’s skin. 


If your dog is seriously ill, your veterinarian may advise hospitalisation and IV fluid therapy. Blood transfusions are only required in exceptional circumstances. When a brown recluse bite heals, it often leaves behind a scar.


Antivenom is accessible and recommended when a black widow sting is suspected. Your veterinarian may decide to put your dog in a kennel, provide antivenom and fluids via an intravenous catheter, check for allergic responses to the drug, and treat muscle spasms.


Regular pest control around your home and property can help avoid bug bites and spiders. If you reside in a spider-infested area, keep your dog away from woodpiles.

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