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What happens after a black widow spider bite

Share on Pinterest Black widows like woodpiles, rocks, and outhouses, so take care around these places.

Spider Bite Pictures: Appearance and Emergency Signs

Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.

Updated on March 01, 2023

Michael Menna, DO, is a board-certified, active attending emergency medicine physician at White Plains Hospital in White Plains, New York.

Spider bites can look a lot like other insect bites as well as different types of skin rashes or lesions. Photographs of a spider bite can help you determine if a bite is serious (such as those caused by the black widow spider or brown recluse spider) or non-serious (as is typically the case).

This article provides pictures of different spider bites and describes the signs and symptoms. It also covers ways to tell if a skin rash or lesion is not caused by a spider.

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Disclaimer

Unless you actually see a spider bite you, the only real way to tell if you’ve been bitten is to have it checked by a healthcare professional.

What Does a Spider Bite Look Like?

Spider venom acts differently in humans than bites from a mosquito or flea or a sting from a hornet or bee. Even so, there may be some overlap in symptoms.

The following are some of the “tell-tale” signs and symptoms of a spider bite:

An Expanding Lesion

There are many different things that can cause a lesion to expand or spread. Though an expanding lesion is common in some spider bites (including a brown recluse spider bite), it can also occur with certain skin infections like impetigo .

If you are unsure whether a lesion is growing, draw a line around it and monitor for any changes over the coming hours. Record the time so that you can report back to your healthcare provider if, in fact, the lesion is spreading.

A Bullseye Rash

A bullseye rash—known as erythema migrans —can be a sign of a spider bite. These are characterized by a small area of redness and swelling encircled by a “halo” of reddened skin.

Bullseye rashes are most common in tick bites that cause Lyme disease but can also occur with certain spider bites.

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

Jake from Atlanta

Fang Marks

Depending on the size and type of the spider that bites you, you may be able to see actual fang marks. These typically present with two small, side-by-side holes in your skin. Fang marks are sometimes seen with black widow bites.

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

Tissue Death

Brown recluse spider bites can cause painful, purplish blisters that break open into ulcers. The ulcer forms as a result of the spider’s venom, which is necrotic , meaning that it kills tissues. Necrosis occurs because the venom kills small vessels, called capillaries, that provide blood to surrounding tissues.

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

Reproduced with permission from © DermNet New Zealand www.dermnetnz.org 2023.

Signs of a Dangerous Spider Bite

Although more than 50 spiders in the United States have venom, their bites are usually not serious and may only cause mild redness, swelling, and pain. Only two spiders in the United States are known to be extremely venomous to humans: the black widow spider and the brown recluse spider.

Brown Recluse Spider Bites

A brown recluse spider is recognized by its dark brown color and violin-shaped body. Its bite may look initially look like a flat area of whiteness (caused by the death of local capillaries and loss of blood flow). It will eventually turn black and blue as blood leaks from the disrupted blood vessels.

Within one to two weeks, the skin may form a purplish or blackish blister. The blister will then erupt and form a painful, open sore (ulcer).

Necrosis can appear either as dry, thick, leathery tissue or as yellow, green, or brownish tissues that are moist, loose, and stringy. When the ulcer heals, it can leave behind an ugly scar.

Other whole-body symptoms of a brown recluse spider bite include:

Headache
Fever
Muscle aches
Joint pain
Nausea
Tiredness

Brown recluse spider bites rarely kill people, but it’s important to get medical attention as soon as you can because a bite can make you very ill.

Black Widow Spider Bites

Black widow spiders are typically black with two reddish triangular markings on the underside of the hourglass-shaped body.

Its bite may look less obvious than a brown recluse spider bite. You may feel a pinprick sensation and see two fang marks accompanied by local redness and swelling.

Black widow venom works quickly, often within an hour, and may cause severe whole-body symptoms like:

Fever with chills
Headache
Nausea or vomiting
Severe muscle cramping
Profuse sweating
Severe chest, back, or abdomen pain

A black widow spider bite is unlikely to kill you but can make you seriously ill and may even require hospitalization.

Wolf Spider Bites

Wolf spiders are recognized by their hairy bodies and multiple eyes (two medium eyes on the top, two large eyes in the middle, and four smaller eyes on the bottom).

Wolf spider bites are usually harmless unless you are allergic to the venom, and most people are not. The bites are about as bad as a bee sting, causing redness and pain that should go away within 24 hours.

Signs That It May Not Be a Spider Bite

If you are bitten by a spider, the chances are that the bite won’t be serious. While this shouldn’t suggest you should wait until symptoms are severe to act, there are ways to reasonably ascertain if a bite is not severe. This is especially true with respect to brown recluse bites.

“NOT RECLUSE” is an acronym for signs and symptoms that a bite is not related to a brown recluse spider. It stands for:

The presence of two or more of these signs almost guarantees that you do not have a brown recluse bite. Some of the same signs may apply to other spider bites.

Numerous Bites

Multiple bites are not typically from spiders, especially not a brown recluse or black widow spider. In cases where there are multiple bites, they could be from insects that travel in groups such as mosquitoes, bedbugs, or chiggers.

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

T. Critchley

Occurrence of the Bite

Brown recluse and black widow spiders prefer cool, dark places and are more likely to be found in an attic, barn, or wood pile. Many bites also occur when you roll over on a spider in bed or put on shoes or clothes that sat out on the floor overnight.

If you have a rash or bite after working outdoors, it’s possible that poison ivy, another type of insect, or a non-venomous spider could be the cause.

Timing of the Bite

Most spider bites occur during mating season from late summer into fall. Brown recluse and black widow spiders are most active between April and October when the weather is warmer and drier. Brown recluses are notoriously inactive during the rest of the year.

Red Centers

With a brown recluse bite, the skin is more likely to be white, purplish, or black rather than red. Though some spider bites can cause a small, red bump, a lesion with a red inflamed center is not suggestive of a venomous spider bite.

In cases like this, a skin infection is a more likely suspect. In fact, a lesion that is swollen, warm to the touch, or red at the center area could very well be due to a staph infection.

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

Danielle from Binghamton, NY

Elevation of the Lesion

If your bite is a raised bump, it may be from a spider—just not a brown recluse. Brown recluse venom causes lesions that are more often flat or slightly concave due to the destruction of underlying blood vessels and tissues.

Chronic Symptoms

If it takes a really long time for the lesion to heal, it might not be due to a brown recluse bite. Most brown recluse bites heal within three weeks and even the biggest ones heal within three months.

Similarly, symptoms of a black widow spider bite usually take a few days or weeks to resolve.

Large Lesions

Brown recluse bites are known for having dead tissues in the center of the lesion. However, the lesion itself is not going to be bigger than 10 centimeters across (roughly 4-1/2 inches).

Skin Ulceration

Venom from a brown recluse spider can cause blistering and the formation of a single ulcer. But this process is a slow one that takes an average of seven to 14 days. If you have a bite that ulcerates before then, it’s probably not from a brown recluse.

Swelling

Brown recluse bites typically only cause significant swelling if the bite is on the head or feet. If you have swelling between the neck and ankles, it is not likely to be from a venomous spider.

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

Exudates

Though some spider bites cause blisters, brown recluse bites are known for being dry in the center. If the lesion is oozing pus, blood, or fluids (referred to as exudates), it’s very unlikely to be a brown recluse spider bite.

A skin ulcer that is oozing or causing local swelling could be from an allergic reaction or a skin infection.

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

When to Call a Doctor

While not many insect bites will require immediate medical attention, there are some situations where you should always seek care:

If you believe that you’ve been bitten by a venomous insect, like a black widow spider
If you develop a bullseye rash (which could be a sign of Lyme disease)
If a skin lesion continues to get worse over a 24-hour period
If you have symptoms of a severe, whole-body allergy known as anaphylaxis

If these symptoms are not involved, it’s probably fine to keep the lesion clean and watch for any changes.

When to Call 911

Call 911 or rush to your nearest emergency room if you develop the following signs and symptoms after getting a spider bite:

Trouble breathing
Wheezing
Lightheadedness or fainting
Trouble standing

Black widow and brown recluse spider bites can be especially dangerous to children because of their smaller body sizes. If you suspect your child was bitten by one, seek emergency care.

How Spider Bites Are Treated

In most cases, a spider bite can be treated at home. A bite from any spider should be immediately washed with soap and water. To aid with healing, apply an antibiotic ointment three times a day.

If you have pain and swelling you can take an over-the-counter nonsteroidal anti-inflammatory drug (NSAID), such as Advil (ibuprofen). If the bite itches, an antihistamine such as Benadryl (diphenhydramine) can help, especially if it keeps you up at night.

Any bite that worsens or becomes infected should be seen by a healthcare provider.

If your bite is caused by a black widow, your healthcare provider may treat it with muscle relaxants or stronger opioid painkillers. In severe cases, an antivenom can be given, but this is usually a last resort as it may cause anaphylaxis.

Summary

Most spider bites are harmless. The exceptions in the United States are bites from the brown recluse spider (which can cause a painful skin ulcer and tissue death) and a black widow spider (which can cause severe, whole-body symptoms). Even so, deaths from a brown recluse and black widow spider bite are rare.

Knowing the signs and symptoms of a venomous spider bite can help you make an informed choice as to whether emergency medical care is needed or not. If in doubt, call or see your healthcare provider.

10 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Rahmani F, Banan Khojasteh SM, Ebrahimi Bakhtavar H, Rahmani F, Shahsavari Nia K, Faridaalaee G. Poisonous spiders: bites, symptoms, and treatment; an educational review. Emerg (Tehran). 2014;2(2):54-8.
Thompson AL. Laboratory testing in monitoring the effects of brown recluse spider bites. Lab Med. 2013;44(4):300-3. doi:10.1309/LMKIW3WIOO13EMMM
Cordeiro FA, Amorim FG, Anjolette FA, Arantes EC. Arachnids of medical importance in Brazil: main active compounds present in scorpion and spider venoms and tick saliva.J Venom Anim Toxins Incl Trop Dis. 2015;21:24. doi:10.1186/s40409-015-0028-5
Shackleford R, Veillon D, Maxwell N, et al. The black widow spider bite: differential diagnosis, clinical manifestations, and treatment options. J La State Med Soc. 2015;167(2):74-8.
Mikkelsen J, Schmidt G, Holmgaard R. Reconstructive considerations following a necrotic spider bite on the face: a case report.Int J Surg Case Rep. 2017;32:76-9. doi:10.1016/j.ijscr.2017.02.023
Seattle Children’s Hospital. Spider Bite.
Cleveland Clinic. Spider bites.
Payne KS, Schilli K, Meier K, et al. Extreme pain from brown recluse spider bites: model for cytokine-driven pain.JAMA Dermatol. 2014;150(11):1205-8. doi:10.1001/jamadermatol.2014.605
Stoecker WV, Vetter RS, Dyer JA. NOT RECLUSE-A mnemonic device to avoid false diagnoses of brown recluse spider bites. JAMA Dermatol. 2017;153(5):377-8. doi:10.1001/jamadermatol.2016.5665
Rader RK, Stoecker WV, Malters JM, Marr MT, Dyer JA. Seasonality of brown recluse populations is reflected by numbers of brown recluse envenomations.Toxicon. 2012;60(1):1-3. doi:10.1016/j.toxicon.2012.03.012

Additional Reading

Murphy C, Hong J, Beuhler M. Anaphylaxis with Latrodectus Antivenin Resulting in Cardiac Arrest. J Med Toxicol. 2011;7(4):317-321. doi:10.1007/s13181-011-0183-1
Vetter R, Swanson D, Weinstein S, White J. Do spiders vector bacteria during bites? The evidence indicates otherwise. Toxicon. 2015;93:171-174. doi:10.1016/j.toxicon.2014.11.229

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.

What happens after a black widow spider bite?

The black widow spider is probably the most venomous spider in North America. Black widows thrive in temperate climates, so they are most common in the south and western regions of the United States.

People may find them in grape vineyards, outdoor toilets, or in other sheltered areas where debris builds up. These areas are perfect for the spiders to build webs and trap prey.

The black widow is famous for its name, given because the female spiders are known to kill and eat males sometimes after mating. Its shiny black body is also easily recognizable.

People can easily tell it apart from other spiders because the black widow has a reddish hourglass-shaped mark on its body. It can also have red and white stripes or spots on the upper part of its body.

Although people often fear the black widow for its venomous bite, it is less deadly than many believe. A black widow’s bite can be harmful, but it is rarely fatal.

Share on Pinterest The black widow spider is easy to recognize from its markings.

Black widow spiders are not often aggressive. They most commonly bite people out of self-defense. Some experts would call the spider shy, as it would rather choose not to bite humans.

“They have no reason to bite us unless they’re threatened,” says Catherine Scott, an arachnologist at Simon Fraser University in British Columbia, Canada, in a Live Science interview. “We pose a much greater threat to them than they do to us.”

Simply coming into close contact with a black widow isn’t necessarily dangerous. Their bite is usually defensive.

People are most at risk for getting bitten when they squeeze or pinch the spider’s body, according to one study published in 2014.

The authors found that even repeated poking was not enough to cause a bite, but accidentally sitting on or grabbing a black widow when reaching for something else can lead to a bite.

Nevertheless, it is best not to touch the black widow with bare hands, and the best way to avoid a bite is to avoid touching the spider altogether.

Anyone who has to be in contact with a black widow should try letting the spider move on its own, or use a dull object to lead it outside.

Children and older people are most at risk of death from a bite. These groups should avoid being in contact with black widows as much as possible.

All spiders have hollow fangs to inject venom into their prey. Most spiders’ fangs are not strong or long enough to break human skin. The black widow’s fangs are different, however.

According to the United States Office of Safety and Health Administration (OSHA), a person may notice some pain when the spider bites, or they may not notice anything at all. Sometimes, two red puncture marks will be visible.

Some people may not realize the spider has bitten them until later. But, 30 to 40 minutes later redness, swelling, and pain might start to radiate from the site.

According to the American Association of Poison Control Centers, not all black widow bites are venomous.

Firstly, only the females will bite. In addition, venom is precious to a spider. The spider will choose when to inject venom and how much, if at all. The black widow saves its venom for when it feels its life is in danger.

Apply first aid

If possible, people should apply first aid at home while waiting for medical help.

People should take the following steps, as far as possible:

Wash the bite site with soap and water.
Wrap ice or an ice pack in a clean cloth and apply it to the bite site. This can slow the rate at which the venom spreads through the body.
If the area is not getting proper blood flow, reduce the amount of time the ice is applied.
Raise the area where the bite is and keep it still.
Apply an antibiotic cream or lotion to the bite to help prevent an infection.
Take an over the counter pain medication for pain.
Take an antihistamine for itching.
Watch the symptoms for any worsening.

If possible, people should put the spider or any remnants of it in a secure container. Giving this to a doctor can help them to provide suitable treatment.

After arriving at the hospital, a doctor or nurse will take vital signs, including their temperature, blood pressure, pulse, and breathing rate.

In some cases, the doctor will order tests, such as:

a urine test
a blood test
a chest or upper body X-ray
an electrocardiogram (EKG)

The person may need:

pain relief medication to treat the symptoms
oxygen
IV fluids

If someone is experiencing severe symptoms, the doctor may give them an antivenin.

This type of medication contains antibodies that help treat the effects of a poison. However, it can sometimes cause severe allergic reactions, so the doctor may prefer not to use it.

In 2011, authors of a case series published in The Permanente Journal noted that a new antibody based antivenom was being developed that should have a lower risk of sensitivity.

People with a heart condition may need to spend time in the hospital.

Share on Pinterest Black widows like woodpiles, rocks, and outhouses, so take care around these places.

Black widow spiders do not usually live in people’s houses, but they are relatively common in the United States in yards, woodpiles, sheds, and so on.

They may also be present at campgrounds and other outdoor locations. People who work outside should be careful to avoid them.

Tips for reducing the risk include:

shaking out all shoes, clothing, and blankets before use, especially if they have been in storage for a while
applying insect repellant to clothes and shoes
using gloves and clothes that cover the body while cleaning out woodpiles and outhouses
looking behind any garden furniture before cleaning or sweeping

Severe symptoms will improve within a few days. Milder symptoms can last for a few weeks.

The individual will be able to go home as the doctor sees fit.

Even with treatment, a bite can be life-threatening for younger children, those who are already unwell, and older people.

Last medically reviewed on September 26, 2018

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Occupational Safety and Health Administration (OSHA). (2005, October). Black widow spider bite [Fact sheet]
https://www.osha.gov/OshDoc/data_Hurricane_Facts/black_widow_spider.pdf
Mowry, J. B., Spyker, D. A., Cantilena Jr., L. R., McMillan, N., & Ford, M. (2014). 2013 annual report of the American Association of Poison Control Centers’ national poison data system (NPDS): 31st annual report. Clinical Toxicology, 52, 1032–1283
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Nelsen, D. R., Kelln, W., & Hayes, W. K. (2014, March). Poke but don’t pinch: risk assessment and venom metering in the western black widow spider [Abstract]. Animal Behaviour, 89, 107-114
http://www.sciencedirect.com/science/article/pii/S0003347213005733
Offerman, S. R., Daubert, G. P., & Clark, R. F. (2011, Summer). The treatment of black widow spider envenomation with antivenin Latrodectus Mactans: A cases series. The Permanente Journal, 15(3), 76–81
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3200105/
Palermo, E. (2015, May 29). Black widows’ bad rap: 4 misconceptions about the spider
http://www.livescience.com/51014-black-widow-spiders-misconceptions.html
What’s a black widow spider? (n.d.) Retrieved from
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What happens after a black widow spider bite