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Spider Bites on Dogs: How to Identify Them

dog looking at spider
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When it comes to avoiding biting and stinging insects, dogs don’t have the best track record. Our curious canines trample on ant hills, hunt for scorpions, and chase bees. This behavior typically results in ant bites, scorpion stings, and bee stings

If dogs aren’t careful, certain species of spiders can also bite and cause inflammation and discomfort. 

All of these insect stings and bites cause similar signs in dogs. In fact, they are often indistinguishable from each other. The symptoms of the whole group are labeled “insect bite hypersensitivity” by veterinarians (even though technically a spider is not an insect but an arachnid).

However, if you’re concerned about spider bites on dogs, this article explains the types of spiders that bite dogs, the symptoms associated with spider bites, and whether these bites can be dangerous for our canine companions.

Do Spiders Bite Dogs?

Spiders most definitely bite dogs. But fortunately most bites are very mild, just as they are for humans. In fact, spider bites are usually indistinguishable from ant bites. 

Bites on the face tend to cause more severe symptoms than ones to the feet or tail. Puppies and very small dogs are more likely to have reactions to spider bites due to their small size.

In warmer areas, spiders are active year-round indoors and out. In colder climates spiders can take refuge from the weather in barns, garages, and homes. Spiders such as wolf spiders, garden spiders, and daddy long legs are found throughout the United States, but they do not have “medically significant” bites.

What Does a Spider Bite Look Like?

Spider in a web

When spider bites cause a reaction on a dog, they look like small (pea-sized) raised bumps that are pink or red. You are very unlikely to see two fang marks. The area may be warmer than the surrounding skin and your dog may be sensitive to touch. Spider bites do not cause bleeding unless your dog chews or scratches the area raw. 

Spider bites on dogs typically look the same as ant bites and bee stings. Spider bites are most likely to occur on a dog’s paw or face. 

Small scratches that cause skin irritation are often confused for spider bites as are zits and other types of skin infections. Similarly, thorns and other sharp plant bits can cause wounds that are mistaken for spider bites.

Symptoms of Spider Bites on Dogs

Most of the time insect and spider bites cause a small red, raised bump on the skin that is itchy or painful. A dog may try to chew at the area or may hold up the affected limb when walking. 

Without these more obvious signs, we may not even know that a dog has been bitten. Though many types of spiders release venom when they bite, it is not enough to cause more than a mild, temporary irritation to most dogs.

Symptoms of spider bites tend to be mild. If the bite is on a limb the dog may limp or refuse to put weight on the leg. Bites on the face may cause local swelling. Rarely, more severe symptoms are possible including vomiting, diarrhea, and difficulty breathing.

Venomous Spider Bites on Dogs

black widow spider

The two species of spiders in the United States that contain strong enough venom to cause injury to dogs are the brown recluse spider and the black widow spider. Just as in people, these spiders can cause severe pain and tissue damage. The severity of the injury depends on the amount of venom released by the spider, the size of the dog, and the location of the bite.

Black widow spiders are found throughout the continental United States. Brown recluse spiders are most common in the Southwest, but their range extends through the Southern states and Midwest.

Brown recluse bites cause a red bullseye pattern and can lead to deep ulcers of the skin or skin necrosis (cell death). Black widow spider bites cause abdominal discomfort and muscle rigidity followed by paralysis. 

Fortunately bites from venomous spiders are very rare in the United States and serious consequences of those bites are even more uncommon. Both of these species of spiders prefer to run away and hide rather than attack, so a dog has to be persistent to be bitten by them. 

While it is very rare for dogs to receive severe bites from brown recluse or black widow spiders, both can cause serious symptoms. Brown recluse venom causes local tissue damage and can lead to local tissue necrosis. These wounds require intensive management by a veterinarian and may take several weeks to months to resolve. Black widow venom is a neurotoxin. It causes the muscles to tense and then become paralyzed. Black widow venom at a high enough dose can be fatal but this is exceedingly rare.

What to Do if a Spider Bites Your Dog

Bites from non-venomous spiders usually do not require any treatment. Symptoms will go away within an hour or so. If you suspect your dog has been bitten by a spider (or an ant), the wait-and-see approach is usually appropriate. If symptoms progress beyond a mild itch or a very small bump then you should call your veterinarian or an emergency clinic. 

The exceptions would be if your dog is allergic to spiders or was in an area with known venomous spiders. Then you should treat the spider bite as an emergency and take your dog to the veterinarian immediately.

How to Treat a Spider Bite on a Dog

Dog chewing spider bite

Most spider bites do not require any treatment. If your dog is itchy or uncomfortable, a dose of an antihistamine can make them feel better faster (your veterinarian can recommend which type of antihistamine to keep at home for these types of situations and can calculate the appropriate dose for your dog). 

Icing the area can also help reduce itch or pain. Never put ice directly on your dog’s skin, wrap the ice in a towel and apply that to the skin instead. Ointments are not usually recommended because dogs will lick them off. 

Venomous spider bites should be treated by your veterinarian. Treatment may include wound management, pain control, and supportive care. There is an antivenom available for black widow spider bites. Full recovery from a black widow bite can take several weeks. Most of what we know about treating black widow and brown recluse spider bites is extrapolated from human medicine because the occurrence is so rare in dogs.

How to Prevent Spider Bites on Dogs

It is impossible to completely prevent spider bites. However, you can take steps to make your home and yard less hospitable to spiders. 

Do not keep piles of brush or wood where your dog frequents, as spiders like to make their homes in these piles. Keeping your grass mowed short also reduces the risk of spider and insect bites. Keep your dog out of sheds, barns, and other structures that provide good homes for spiders. 

If you suspect or have seen venomous spiders, call a pest control company for appropriate removal. The pest control company can then offer additional advice on how to reduce the risk of those spiders returning. 

In general, risks from spider bites are low. Since it is unlikely that you will witness a spider bite, use your best judgment if you suspect a bite on your dog. If symptoms are mild then you can probably just monitor. If symptoms progress beyond a small itchy bump, then it is time to take your dog to a veterinarian.