Table of ContentsView AllTable of ContentsAppearanceSymptoms of Dangerous BitesHarmless Spider BitesOther CausesWhen to Call a DoctorTreatment
Table of ContentsView All
View All
Table of Contents
Appearance
Symptoms of Dangerous Bites
Harmless Spider Bites
Other Causes
When to Call a Doctor
Treatment
A serious bite from theblack widoworbrown reclusespider can cause severe skin changes and other problems. The effects of non-serious bites, which are more common, lead to minor symptoms.
While reviewing typical reactions to spider bites, it’s important to also understand signs that something isnota spider bite.
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 likeimpetigo.
If you’re 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
This photo contains content that some people may find graphic or disturbing.See PhotoJake from Atlanta
This photo contains content that some people may find graphic or disturbing.See Photo
This photo contains content that some people may find graphic or disturbing.
Fang Marks
Fang marks are sometimes seen with female black widow bites or male and female brown recluse spiders, which have hollow fangs (chelicerae).Venom is injected into your bloodstream through these fangs.
This photo contains content that some people may find graphic or disturbing.See PhotoExodog
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 isnecrotic, meaning that it kills tissues.Necrosisoccurs 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.See PhotoReproduced with permission from © DermNet New Zealandwww.dermnetnz.org2023.
Reproduced with permission from © DermNet New Zealandwww.dermnetnz.org2023.
Symptoms of a Dangerous Spider Bite
Only two spiders in the United States are known to be extremely venomous to humans: the black widow spider and the brown recluse spider.
However, in rare instances, you may have an allergic reaction to another common spider, the wolf spider.
Brown Recluse Spider Bites
After a week a brown recluse spider bite may look worse as the skin forms a purplish or blackish blister. The blister will then erupt into 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:
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.
Black widow venom works quickly, often within an hour, and may cause severe whole-body symptoms like:
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 spider bitesare usually harmless. However, if you are allergic, you may develop the following symptoms:
Contact your healthcare provider if you experience any of these reactions.
A variety of spiders are likely to bite if you disturb them. These bites are usually not serious.The American house spider and common arachnids found in nature, such as the following, are not dangerous.
A bite from one of these spiders may only cause mild redness, swelling, and pain.However, even minor spider bites can become infected if you scratch or pick at them.
If you notice increased redness, swelling, or pus, see a healthcare provider to check for an infection.
Signs That It May Not Be a Spider Bite
Numerous Bites
Multiple bites are not typically from spiders. In cases where there are multiple bites, they could be from insects that travel in groups such as mosquitoes,bedbugs, orchiggers.
This photo contains content that some people may find graphic or disturbing.See PhotoT. 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 likely due to poison ivy or another type of insect. However, a garden spider might bite you in these situations if you disturb them.
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, askin infectionis 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 astaph infection.
This photo contains content that some people may find graphic or disturbing.See PhotoDanielle from Binghamton, NY
Chronic Symptoms
If it takes a really long time for the lesion to heal, it is not likely due to a spider bite. Minor bites clear up quickly.
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
Even the most dangerous spider bites do not spread. 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 a spider bite at all.
While not many insect bites will require immediate medical attention, there are some situations where you should always seek care:
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:
How Spider Bites Are Treated
In most cases, a spider bite can be treated at home.
To care for your wound:
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.
12 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto 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/LMKIW3WIOO13EMMMRich, Robert.“What Should I do if I Get a Spider Bite?“Family Doctor.NYC Department of Health.Spiders.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.2017.02.023Payne 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.2014.605Shackleford 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.American Academy of Family Physicians.What should I do if I get a spider bite?.Seattle Children’s Hospital.Spider Bite.National Park Service.Field Guide to Spiders and Scorpions.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.2016.5665Johns Hopkins Medicine.Spider bites.Additional ReadingMurphy C, Hong J, Beuhler M.Anaphylaxis with Latrodectus Antivenin Resulting in Cardiac Arrest.J Med Toxicol.2011;7(4):317-321. doi:10.1007/s13181-011-0183-1Vetter 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
12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto 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/LMKIW3WIOO13EMMMRich, Robert.“What Should I do if I Get a Spider Bite?“Family Doctor.NYC Department of Health.Spiders.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.2017.02.023Payne 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.2014.605Shackleford 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.American Academy of Family Physicians.What should I do if I get a spider bite?.Seattle Children’s Hospital.Spider Bite.National Park Service.Field Guide to Spiders and Scorpions.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.2016.5665Johns Hopkins Medicine.Spider bites.Additional ReadingMurphy C, Hong J, Beuhler M.Anaphylaxis with Latrodectus Antivenin Resulting in Cardiac Arrest.J Med Toxicol.2011;7(4):317-321. doi:10.1007/s13181-011-0183-1Vetter 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
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto 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/LMKIW3WIOO13EMMMRich, Robert.“What Should I do if I Get a Spider Bite?“Family Doctor.NYC Department of Health.Spiders.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.2017.02.023Payne 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.2014.605Shackleford 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.American Academy of Family Physicians.What should I do if I get a spider bite?.Seattle Children’s Hospital.Spider Bite.National Park Service.Field Guide to Spiders and Scorpions.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.2016.5665Johns Hopkins Medicine.Spider bites.
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
Rich, Robert.“What Should I do if I Get a Spider Bite?“Family Doctor.
NYC Department of Health.Spiders.
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
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
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.
American Academy of Family Physicians.What should I do if I get a spider bite?.
Seattle Children’s Hospital.Spider Bite.
National Park Service.Field Guide to Spiders and Scorpions.
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
Johns Hopkins Medicine.Spider bites.
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/s13181-011-0183-1Vetter 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
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
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