Which Spider Bites Are Dangerous—and What to Do About Them (2023)

Spider bites are typically not dangerous and cause mild symptoms. In North America, only two spiders inject venom with a bite that can actually make you sick: theblack widow and thebrown recluse.

Spider bite symptoms of redness and itching are common. If these symptoms spread from the bite site, the bite may be more serious and lead to other symptoms. This requires medical attention, as do bites from the two dangerous spiders that cause systemic (bodywide) effects.

This article describes some types of spiders found in the United States and what spider bites look like. It presents spider bite pictures and signs to look for so you can know when to worry about a spider bite.

Which Spider Bites Are Dangerous—and What to Do About Them (1)

What Do Spider Bites Look Like?

Spider bites look different depending on the type of spider. Some spiders have fangs that leave a double mark behind, while others look more like a mosquito bite. Spider bites are typically red and swollen and may have blisters, pus, or discoloration.

Spider Bite Symptoms

It's almost impossible to identify a spider bite based on appearance. That's because bites from all kinds of insects can cause the same symptoms, including:

  • Redness
  • Swelling
  • Itching
  • Pain

Spider bite symptoms can differ depending on the type of spider involved. They can start right away or take hours or more to develop.

Serious Spider Bite Symptoms

Signs that a bite is more serious include:

  • Redness spreading away from the bite
  • Drainage (pus) from the bite
  • Increased pain
  • Numbness or tingling
  • Discoloration around the bite that looks like a halo or a bullseye

Serious spider bites can also be accompanied by abdominal cramps, breathing problems, and full-body reactions, including muscle weakness and fever.

Spider Bite Pictures: Appearance and Emergency Signs

Dangerous Spider Bites

Only two spiders in North America are considered dangerous. These are the black widow and the brown recluse. There are ways to tell if your bite could be from one of these spiders.

Black Widow Spider Bites

In the United States, black widow spiders, females in particular, are considered the most dangerous. While males may be hard to distinguish from other spiders, females have a unique hourglass shape in a red-orange color on their underside.

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Their venom contains a toxin, or poisonous substance, that can cause a systemic reaction. It affects the body's systems and organs beyond the site of the bite itself.

This photo contains content that some people may find graphic or disturbing.

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Black Widow Spider Bite Symptoms

A black widow bite can potentially affect muscle and nerve function. You may notice the following symptoms:

  • Fang marks (tiny twin holes): These are telltale signs that are only visible right after the bite happens, before any swelling or redness occurs.
  • Immediate sharp or moderate pain from the bite itself, followed by swelling and redness at the site 30 to 40 minutes later

When severe symptoms occur, they usually do so within 30 to 60 minutes.

These can include:

  • Sweating
  • Chills
  • Fever
  • Nausea or vomiting
  • Headache
  • Dizziness
  • Musclecramps
  • Rapid pulse or very high blood pressure
  • Exhaustion
  • Stupor or restlessness
  • Shock
  • Severe pain in the abdomen, back or chest

Muscle cramps and spasms near the bite may spread and increase in severity over the course of six to 12 hours.

It is extremely rare for a black widow bite to be fatal. In 2018, there were 1,015 recorded cases of black widow spider bites in the U.S. Six patients had potentially life-threatening symptoms, but none of them died.

Brown Recluse Spider Bites

Brown recluse spiders areonlyfound in the Southeast United States. They are often described as having a violin-shaped mark on the back of their midsections. But they don't always have this mark, and it can be very faint. They are difficult to identify, even for trained spider experts.

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Even though a wound left behind by a brown recluse can look pretty serious, brown recluse spiders are much less likely to cause significant injury than black widows.

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Symptoms of a Brown Recluse Spider Bite

You might not feel anything after a bite at first. Symptoms that can develop over time from a brown recluse bite include:

  • Reddened skin at the site of the bite that may turn into a blister (after four to eight hours)
  • Mild to intense pain and itching that lasts for two to eight hours after being bitten
  • An open sore (ulcer) that causes necrosis (tissue death). This tends to develop in a week or longer, and it can take months to heal.

In some cases, people can have a severe, systemic reaction to brown recluse spider bites. Signs and symptoms include:

  • Fever and chills
  • A rash all over the body that consists of tiny, flat purple and red spots on the skin
  • Nausea or vomiting
  • Joint pain

It's actually easier to figure out when a bite is not from a recluse than when it is. One way to rule out brown recluse bites is to see how your bite matches up with the following qualities. (The first letters of each conveniently spell NOT RECLUSE to make them easier to remember.)

  • Numerous: If there are more lesions than just one or two, they're not from a brown recluse. Brown recluse bites come in ones and sometimes twos.
  • Occurrence: Brown recluse bites usually happen when you disturb the spider. Most of the time these spiders hide in closets or attics, possibly inside boxes. Occasionally, the spider can find its way into a bed and bite a person while they are asleep. If the spider bit you while you were gardening or doing something outside, it's probably not a brown recluse bite.
  • Timing: If the bite didn't occur from April to October, it's very unlikely that it's a brown recluse bite.
  • Red center: Brown recluse bites are almost never red and inflamed in the center of the lesion. Usually, they're pale, blue, or purple. They can be red around the outside. But if it's red in the center, it's probably not a brown recluse bite.
  • Elevated: Brown recluse spider bites are flat or slightly sunken.If a lesion is raised up more than 1 cm above the normal skin surface, it's probably not a recluse bite.
  • Chronic: It takes around three months for a recluse spider bite to heal. If it takes more or less than that, it is unlikely to be a brown recluse bite.
  • Large: The largest areas of necrosis, or dying tissue, are smaller than 4 inches across. A recluse bite can be red and swollen well past that area, but there won't be dead tissue.
  • Ulcerates too early: Brown recluse bites take at least a week to break the skin and crust over. If it's crusty before seven days, it's probably not a brown recluse bite.
  • Swollen: Brown recluse bites are flat or sunken in the middle, not swollen. If it's swollen, especially if it's red, it's not a brown recluse. Bites on the face, especially the eyelids, are exceptions to this rule. Those swell a lot.
  • Exudes moisture: Brown recluse bites are dry, not moist. If it has pus oozing out of it, it's an infection rather than a spider bite.

How to Tell If You Were Bitten by a Brown Recluse Spider

How Do You Tell if You Were Bitten by a Spider?

The truth is, you may not know if it's a spider bite unless you saw or caught the spider. Symptoms of red, swelling, and itchy skin are common to many insect bites. If your symptoms worsen or you have a bodywide reaction, contact your healthcare provider. It's rare to have a life-threatening or fatal reaction from a spider bite, but you may need diagnosis and treatment.

Non-Dangerous Spider Bites

There are more than 40,000 species of spiders in the world, but most of them are too small, or their venom is too weak, to be dangerous to humans.

The following North American spiders may look dangerous but are generally harmless.

Hobo Spiders

The hobo spider (Eratigena agrestis) has a bad reputation for its alleged flesh-eating venom. However, according to scientists at Utah State University, these reports are unfounded.

Native to Europe, hobo spiders were introduced to the Pacific Northwest in the 1930s. They can be found throughout Washington, Oregon, and Idaho and in parts of Montana, Wyoming, and Utah. They are light brown with darker brown markings and legs and a grey abdomen with a distinct yellow pattern. Their body is about a half-inch long, and they run pretty fast.

Hobo spiders weave funnel-shaped webs and commonly hidein wood piles, rock walls, and where tall grass meets the foundation of a building. They are commonly found inside between August and October, usually in the basement, on ground level, or in bathtubs and sinks—they are unable to climb smooth surfaces like walls.

Hobo spider bites look similar to a pinprick or bee sting. Other symptoms may include:

  • Headache lasting two to seven days
  • Pain
  • Redness
  • Twitching calf muscle

In one study, symptoms of hobo spider bites were found to resolve after 12 hours.

Wolf Spiders

Wolf spiders look relatively scary, but their bite is typically harmless unless you are allergic. Originally from Australia, there are about 200 varieties of wolf spiders found across the United States.

Often mistaken for the dangerous brown recluse spider, wolf spiders are typically brown or grey with dark markings or lines. They have hairy bodies that range from 1/2 inch to 2 inches long and multiple eyes—two medium eyes on the top, two large eyes in the middle, and four smaller eyes on the bottom.

Wolf spiders often migrate indoors during the cooler months and can be found around doors, windows, houseplants, basements, and garages. They do not spin webs but huntfor prey.

A wolf spider bite is similar to a pin-prick or bee sting. It may cause temporary numbness, but should not cause any serious issues unless you are allergic (which is rare).

Yellow Sac Spiders

Yellow sac spiders are one of the most common spiders in the United States. It comes in two varieties: Cheiracanthium inclusum and Cheiracanthium mildei.

These small, pale yellow spiders are found in the garden and homes and account for most spider bites.

Bites from C. mildei are relatively harmless and painless—you may not even realize you have been bitten.

C. inclusum bites, on the other hand, can be more serious. The initial bite is often very painful and causes a burning sensation lasting up to an hour. Other symptoms of a yellow sac spider bite include:

  • A blistering rash that develops one to 10 hours after the bite
  • Full-body reactions, including fever, malaise, muscle cramps, and nausea
  • Itching
  • Redness
  • Swelling

Yellow sac spider bites can be mistaken for a brown recluse bite, but the symptoms are not dangerous.


Tarantulas are large, hairy spiders with long legs and multiple eyes. Often depicted in a black and orange striped pattern, tarantulas come in 40 different varieties ranging in color from pale beige to all black.

Tarantulas are often kept as pets but can be found in the wild throughout the southern and Southwestern regions of the United States.

A tarantula bite can leave fang marks and cause throbbing pain that lasts for hours. In addition to biting, tarantulas will also release and toss bristles (urticating setae) that can cause swollen, itchy bumps that can last for weeks.

Despite the pain and irritation, tarantula bites are usually harmless unless you are allergic. Symptoms that warrant immediate medical attention include:

  • Difficulty breathing
  • Itching
  • Low blood pressure and collapse
  • Puffy eyelids
  • Rapid heart rate
  • Rash
  • Severe redness and swelling around the bite location
  • Swelling of the lips and throat

Brown Widow Spiders

The brown widow spider is smaller and lighter than the black widow—and far less dangerous. Ranging in color from tan to dark brown, it has a distinct yellow or orange hourglass on the underside of its abdomen.

The brown widow originated in the southern hemisphere and is found in warm climates. In the U.S., it was initially only seen in Florida, but by 2003, had spread across the southern states to California.

Brown widow bites are not as serious as black widow bites, but they are still very painful. The pain is typically limited to the area near the bite. Full body symptoms, though rare, can occur and include:

  • Abdominal pain and cramping
  • Fever
  • Muscle pain and cramps
  • Painful lymph nodes
  • Weakness in legs and difficulty walking

False Black Widows

False black widow spiders look similar to black widow spiders but without the hourglass marking on their abdomen. They can be found in coastal regions of the Atlantic, Gulf, and Pacific states, as well as in Southern and Western states.

False black widow bites are much less serious than a true black widow but still very painful. The initial bite can cause burning pain with minor swelling around the bite.

Camel Spiders

The sand-colored camel spider can be found in arid climates like the deserts of Southwestern states. Despite their name, they are not actually spiders, but solifugids, and more closely related to a scorpion.

Camel spiders can grow as large as 6 inches and travel up to 10 miles an hour. They have large jaws that resemble crab pincers. Their bite can be quite painful and break the skin. Fortunately, camel spiders are nonvenomous and generally not dangerous.

Jumping Spiders

Jumping spiders are relatively small, fuzzy spiders that look a bit like a Muppet. Found throughout the U.S., they come in an assortment of different colors. They are known for jumping and scurrying about.

Jumping spiders retreat from people when they are approached and generally do not bite humans unless cornered or handled. If they do bite, you may experience minor pain, itching, swelling, and redness for a day or two.

When to See a Healthcare Provider

While most spider bites are not deadly, they can still be serious.

Contact your healthcare provider if you have symptoms that get worse at the site of the bite or have a ring around them that looks like a halo or bullseye.

Get immediate medical attention if you have a bodywide reaction or begin to have more severe symptoms, including muscle cramps, heart rate changes, fainting, vomiting, severe pain, or mental confusion.

A severe allergic reaction, called anaphylaxis, can occur with spider bites in some people. This is a life-threatening emergency. Call 911 for help if you experience symptoms that include:

  • Hives
  • Shortness of breath
  • Wheezing
  • Weakness

Skin rashes and sores, like boils from infections, are frequently misdiagnosed as spider bites. This is because of similar symptoms and the fact that there are no means to test for the presence of spider venom.

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How to Treat Spider Bites

Most spider bites can be treated at home like any other bug bite. They usually heal on their own in about a week unless the bite is from a brown recluse.

Here's what to do if you think you've been bitten:

  • Clean the wound with soap and water.
  • Apply an antibiotic ointment (like Neosporin) to help prevent infection.
  • Use a cool compress on the bite for no longer than 15 minutes at a time to reduce pain and swelling.
  • If the wound is on a limb, try to elevate it.
  • Take an over-the-counter pain reliever like Advil (ibuprofen) or Aleve (naproxen sodium) to relieve discomfort.

If you notice that the wound is getting worse or you develop any systemic symptoms like fever, chills, or just feeling unwell overall, call your healthcare provider. Oral antibiotics used to treat spider bites, such as Keflex (cephalexin), may be prescribed for infection.

Other medications, such as prednisone, also may be used depending on your symptoms.

It's also a good idea to get up-to-date on yourtetanus vaccination, too. Bites from insects or animals can sometimes transmit the bacteria that causes tetanus.

How Long Do Spider Bites Last?

For non-dangerous spider bites, the pain and swelling last about one to two days. A brown recluse spider bite usually heals within eight weeks. For black widow bites, your symptoms will typically get better in two days and disappear in five days, but you may notice mild symptoms for weeks.

How to Prevent Spider Bites

Spiders only bite when they feel threatened. In other words, they do not seek out people to "attack."

The best way to avoid encountering brown recluse or black widows is to understand their habits.

Both of these types of spiders tend to prefer quiet, undisturbed areas such as closets, garages, basements, and attics. They may also congregate in stacks of firewood and other items next to the outside of houses.

Here are some tips for reducing your risk of encountering these spiders:

  • Reduce clutter in indoor areas where they may gather. Store items in plastic tubs rather than cardboard boxes, which are easier for spiders to get into and hide.
  • Keep firewood and other items in places where they do not make direct contact with the outside of your home. Shrubs, vines, and tree limbs touching the house should also be trimmed back since these give spiders shelter and a convenient bridge to your house.
  • Install tight-fitting window screens and door sweeps to keep spiders from entering your home.
  • Clean your house routinely, using a vacuum in areas where spiders and their egg sacs may be.


Only two spiders in the United States are capable of causing serious bites: the black widow and the brown recluse. Thankfully, dangerous or life-threatening reactions are rare.

While other spider bites may certainly not be without bothersome symptoms, they are not considered dangerous except for the fact that they—like any bug—can cause an allergic reaction in some people.

It's not uncommon for someone to think they have a spider bite when they really have a skin infection. If your bite is concerning, see a healthcare provider.

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