How Poisonous Is A Brown Recluse Spider?

Brown Recluse Spiders: Facts, Bites & Symptoms

The brown recluse spider is well-known for its appearance and poisonous bite. It is the most common and widespread of the brown spiders, but it is found only in the south and central United States.

Brown recluse spiders live in a region comprising Kansas, Oklahoma, Texas, Louisiana, Arkansas, Missouri, Mississippi, Alabama and parts of Georgia, Tennessee, Kentucky, Ohio, Indiana, Illinois, Iowa and Nebraska. According to the entomology department at the University of California, Riverside, if you do not live in those areas, «it is highly unlikely that you have a recluse spider. It is possible but incredibly unlikely.»

This map shows the range of different species of recluse spiders, including the brown recluse (reclusa, in red); Texas recluse (devia, in yellow); Big Bend recluse (blanda, in green); Apache recluse (apachea, in light blue); Arizona recluse (arizonica, in blue); and desert recluse (deserta, in purple). (Image credit: University of California, Riverside)


The brown recluse is part of the Loxosceles genus of spiders. Members of this group have violin-shaped markings on the top of their cephalothorax (fused head and thorax) and may be informally referred to as fiddleback or violin spiders, according to The Ohio State University Extension Entomology Department.

The brown recluse’s violin marking can vary in intensity depending on the age of the spider, with mature spiders typically having dark violin shapes, according to The Ohio State University. The violin shape points toward the spider’s bulbous abdomen. The violin shape is easy to misinterpret, so it is best to look at the eyes when determining if a spider is a brown recluse.

The recluse’s eyes are one of its most distinctive physical characteristics. «They have six eyes, instead of eight like most spiders,» said entomologist Christy Bills, invertebrate collections manager at the Natural History Museum of Utah. Other types of spiders have eight eyes arranged in rows of four. Recluses, however, have six equal-size eyes arranged in three pairs, called dyads, in a semicircle around the front of the cephalothorax.

Another distinguishing characteristic of the brown recluse spider is its uniformly colored abdomen (though the shade of brown varies from spider to spider) covered in fine hairs, which give it a velvety appearance. Their long, thin legs are also covered in fine hairs. According to the Integrated Pest Management Program at The University of California, Berkeley, the scientific name Loxosceles means «slanted legs,» and refers to the fact that recluse spiders hold their legs in a slanting position when at rest. Bills also noted that the brown recluse’s legs do not have spines, only fine hairs.

Ohio State University reports that the brown recluse is typically about three-eighths of an inch long and about three-sixteenths of an inch wide (about 1 centimeter long and half a centimeter wide), with males being slightly smaller than females but possessing longer legs.


According to the Integrated Taxonomic Information System (ITIS), the taxonomy of brown recluse spiders is:

  • Kingdom: Animalia
  • Subkingdom: Bilateria
  • Infrakingdom: Protostomia
  • Superphylum: Ecdysozoa
  • Phylum: Arthropoda
  • Subphylum: Chelicerata
  • Class: Arachnida
  • Order: Araneae
  • Family: Sicariidae
  • Genus & species: Loxosceles reclusa


The brown recluse gets its name from its color and its «shy nature,» Bills said. «Most spiders go out of their way to avoid humans, which makes sense, considering we are thousands of times larger than they are and don’t have a great record of behaving politely toward them.»

Brown recluses often hide in dark, secluded places, like under porches or deep in closets. The brown recluse thrives in man-made areas, and may be found under trash cans, tires, etc. It is primarily nocturnal and lays its eggs from May to July.

Brown recluse spiders get around by hitchhiking on furniture boxes and other items from infestedstructures, according to the Illinois Department of Public Health. They are well adapted for establishing themselves by hitchhiking. They are long-lived, can go for many months without eating, and are adapted to the hot, dry conditions found in many structures. What’s more, a female brown recluse needs to mate only once to produce eggs throughout her life, and can produce 150 or more spiderlings in a year. Thus, a single female hitchhiking into a structure is all it takes to establish an infestation. The need to inspect items before moving them in is clear.

Once established within a structure, brown recluses are often difficult to control. Though hundreds of brown recluses may be present in a house, they may not be easily observed because of their reclusive, nocturnal habits.

Brown recluse bite

The brown recluse has a venomous bite, and anyone bitten should seek immediate emergency medical help, according to the National Institutes of Health.

Like most spiders, the brown recluse typically only bites when disturbed — though it is possible to inadvertently threaten them. The Texas A&M AgriLife Extension Program reports that this may happen if a spider is caught in bedding or clothing.

«People react differently to bites,» Bills said. According to The Integrated Pest Management Program at UC Berkeley, 90 percent of bites heal without medical attention or scarring. Reactions to a brown recluse bite vary depending on the amount of venom injected and the individual’s sensitivity levels, reports The Ohio State University. Some people may experience a delayed reaction, others an immediate reaction, and others no reaction at all. Many brown recluse bites leave a small red mark that heals quickly, and the vast majority of bites do not leave scars.

For those with higher sensitivity levels, a small white blister appears at the bite site soon after the bite. The tissue may become hard. Lesions are dry, blue-gray or blue-white patches with ragged edges surrounded by redness. This color pattern has yielded the nickname «red, white and blue,» and, in severe reactions, the bite site can develop a «volcano lesion,» according to The Ohio State University. The damaged tissue becomes gangrenous and leaves an open wound that can be as large as a human hand. It can take eight weeks or longer for full recovery, and scars may result.

See also:  Wolf Spider What Do They Eat?

According to the NIH, symptoms of a brown recluse bite may include itching, chills, fever, nausea, sweating and a general feeling of discomfort or sickness.

After being bitten by a brown recluse spider, a 10-year-old girl in Mexico required two medical procedures to remove blackened, dead tissue from her leg. (Image credit: The New England Journal of Medicine ©2013)


There is no effective commercial antivenin. If you are bitten, the NIH recommends calling 911 or poison control or getting to an emergency room immediately.

The NIH says you should wash the area of the bite with soap and water, then wrap ice in a washcloth and place it on the bite area for 10 minutes. Remove the washcloth for 10 minutes, and repeat the process.

Then, go immediately to the emergency room and bring the spider, if possible, for identification purposes.

For the latest information on brown recluse spiders and other arachnids, visit:

Editor’s Note: If you’d like more information on this topic, we recommend the following book:

Additional resources

  • University of California, Riverside: How to identify brown recluse spiders
  • NIH: Picture of brown recluse spider bite
  • Illinois Department of Public Health: Brown Recluse and Black Widow Spiders

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How Dangerous Are Brown Recluse Spiders?

For such a tiny spider, the brown recluse sure has a big reputation? Perhaps you’ve heard some of the stories. Or, perhaps, you’ve seen some of the unsavory pictures of brown recluse bite wounds. It is also quite possible that you don’t believe any of it, and you are of the opinion that it is no big deal to have brown recluse in your home. Either way, we hope to dispel the myths with this article and get to the truth about how dangerous it is to have brown recluse living in your home.

What Makes the Brown Recluse Dangerous?

  • Tissue-Destroying Bites
  • Fast-Moving
  • Ability to Hide

Tissue-Destroying Bite?

While this is definitely a spider that should be respected, there has been more than a little exaggeration when it comes to the threat of the brown recluse. You are probably aware that brown recluses have venom with necrotic properties. That means the venom destroys living tissue. But the truth is that it doesn’t always create a large wound. A bite from a brown recluse can actually be minor, with no spreading of tissue damage. So, does that mean it is no big deal to be bitten by one of these spiders? Well, that depends on where you are bitten. Even a small necrotic wound on the face can lead to a disfiguring scar. And that is not something anyone needs.

Fast-Moving with Great Eyesite?

You may have heard stories that the brown recluse is a fast-moving spider with great eyesight. While this is true, they are also reclusive, as their name suggests. If they notice you coming, they’re going to run in the opposite direction. This helps to reduce bites from these spiders. But, when a brown recluse is trapped, it will bite.

Ability to Hide?

The biggest danger brown recluse pose is actually not in how venomous they are or how skilled they are at hunting prey. It is in how well they can survive in human dwellings. Most homes do not have food and water at levels that are sufficient for many bugs, but the brown recluse spiders can tolerate as much as six months in drought conditions and limited food resources. This, combined with its ability to reproduce quickly, can create a significant infestation inside a home. And, while one or two brown recluses in a home will not likely lead to a bite incident, dozens, or even hundreds, could.

How to Identify Brown Recluse

When brown spiders appear in your home, it is important to determine whether or not they are brown recluse spiders. If you see the spider up close, you can look to see if it has the upside-down violin shape on its back. This marking will be dark brown on its light tan skin. You can also look for its six eyes—two of which are close together in the center and may give the appearance of only three eyes.

Brown recluse are a little bigger than a quarter. And, unlike other brown spiders, the recluse is hairless. If you see a smooth, fast-moving brown spider, it is likely to be a brown recluse.

How to Avoid A Brown Recluse Bite?

Though there can be quite a bit of hysteria surrounding the brown recluse, it has no interest in hunting you. You are most likely to get a bite when you bring yourself into contact with one of these spiders. Here are a few ways you can prevent this from happening.

  • Check between your sheets before you slide into bed.
  • Shake your shoes before you slide your feet into them.
  • Shake out clothing before you put it on, especially if it has been lying on the bed or over a chair.
  • Be careful when picking up a damp towel from the floor. If possible, refrain from leaving wet towels and clothing on the floor at all.
  • If you get a box from the attic or basement, be cautious when opening it.
  • Look before you sit. The last thing you want to do is share a seat with a brown recluse spider.

How to Keep Brown Recluses Out of Your Home

Though brown recluses aren’t as bad as the myths would have us believe, this is still a pest control problem you definitely don’t want to get wrong. We strongly recommend that you contact a pest control company to handle a brown recluse infestation. Through a process of inspection, treatment, and monitoring, a certified professional will be able to determine that the problem has been resolved.

We also recommend that you choose a pest control company that is QualityPro certified. This is a third-party certification from the National Pest Management Association for excellence in pest control service and business practices.

If you’re in our Missouri service area, let the QualityPro-certified team here at Rottler Pest & Lawn Solutions help you make sure that your brown recluse issue is resolved, the first time. With our St. Louis exterminators, you’ll always get the highest level of pest control with the highest level of service. Schedule your free inspection today.

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Brown Recluse Spider Bite

Spider Bite: Brown Recluse Spider Bite Related Articles

  • Facts
    • Facts on Brown Recluse Spider Bite
  • Causes
    • Brown Recluse Bite Causes
  • Symptoms
    • What are the symptoms of a brown recluse spider bite?
  • Treatment
    • Should I see a doctor if I’ve been bitten by a brown recluse?
    • What is the treatment for brown recluse spider bites?
    • What is the follow-up for a brown recluse follow-up?
  • Diagnosis
    • How is a brown recluse spider bite diagnosed?
  • Home Remedies
    • Are there home remedies for a brown recluse spider bite?
  • Prevention
    • How do I prevent a brown recluse spider bite?
  • Prognosis
    • What is the prognosis for a brown recluse spider bite?
  • Pictures
    • What does a brown recluse look like?
    • Pictures of Brown Recluse Spider Bite 11 Days to 10 Months
  • Stages
    • Pictures of Brown Recluse Spider Bite First Nine Days
  • Guide
    • Brown Recluse Spider Bite Topic Guide
    • Doctor’s Notes on Spider Bite: Brown Recluse Spider Bite Symptoms

Facts on Brown Recluse Spider Bite

Most spiders are absolutely harmless to humans. In fact, of the over 20,000 different species of spiders that inhabit the Americas, only 60 are capable of biting humans. Within that small group, only four are known to be dangerous to humans: the brown recluse, the black widow, the hobo or aggressive house spider, and the yellow sac spider. Within this select group, only the brown recluse and the black widow spider have ever been associated with significant disease and very rare reports of death.

  • Deaths from brown recluse spiders have been reported only in children younger than seven years. Brown recluse spiders are native to the Midwestern and Southeastern states. Documented populations of brown recluse spiders outside these areas are extremely rare. In recent years controversy has arisen over the appearance of brown recluse spiders in California and Florida. At this time most experts agree that the brown recluse is not endemic to these areas. With increasing travel, individual spiders and spider bites can be found in areas where the spider is not endemic, and health care practitioners should consider this when treating suspected bites.
  • Fewer than 10 individual spiders have ever been collected outside of these native states. Most false sightings are due to confusion with one of the 13 other species found in the same family.
  • The most common non-brown recluse spiders are the desert recluse found in Texas, Arizona, and California, and the Arizona recluse. No deaths have ever been reported from non-brown recluse spiders. Bites from these cousins produce mild to moderate local skin disease.

Features: Brown recluse spiders are notable for their characteristic violin pattern on the back of the cephalothorax, the body part to which the legs attach. The violin pattern is seen with the base of the violin at the head of the spider and the neck of the violin pointing to the rear. These small non-hairy spiders are yellowish-tan to dark brown in color with darker legs. They have legs about one inch in length. The name of the genus, Loxosceles, means six eyes. Most other spiders have eight eyes. Yet this unique feature of the brown recluse is lost on the casual observer because the eyes are too small to be seen with the naked eye.

Habits: These spiders are not aggressive and bite only when threatened, usually when pressed up against the victim’s skin. They seek out dark, warm, dry environments such as attics, closets, porches, barns, basements, woodpiles, and old tires. Its small, haphazard web, found mostly in corners and crevices, is not used to capture prey. Most bites occur in the summer months.

Brown Recluse Bite Causes

The brown recluse venom is extremely poisonous, even more potent than that of a rattlesnake. Yet recluse venom causes less disease than a rattlesnake bite because of the small quantities injected into its victims. The venom of the brown recluse is toxic to cells and tissues.

  • This venom is a collection of enzymes. One of the specific enzymes, once released into the victim’s skin, causes destruction of local cell membranes, which disrupts the integrity of tissues leading to local breakdown of skin, fat, and blood vessels. This process leads to eventual tissue death (necrosis) in areas immediately surrounding the bite site.
  • The venom also induces in its victim an immune response. The victim’s immune system releases inflammatory agents-histamines, cytokines, and interleukins-that recruit signal specific disease-fighting white blood cells to the area of injury. In severe cases, however, these same inflammatory agents can themselves cause injury. These secondary effects of the venom, although extremely rare, can produce these more significant side effects of the spider bite:
    • Destruction of red blood cells
    • Low platelet count
    • Blood clots in the capillaries and loss of ability to form clots where needed
    • Acute renal failure (kidney damage)
    • Coma
    • Death

What are the symptoms of a brown recluse spider bite?

Brown recluse spider bites often go unnoticed initially because they are usually painless bites. Occasionally, some minor burning that feels like a bee sting is noticed at the time of the bite and a small white blister develops at the site of the bite. Symptoms usually develop two to eight hours after a bite. Keep in mind that most bites cause little tissue destruction.

Victims may experience these symptoms:

  • severe pain at bite site after about four hours,
  • severe itching,
  • nausea,
  • vomiting,
  • fever, and
  • myalgias (muscle pain).

Initially the bite site is mildly red and upon close inspection may reveal fang marks. Most commonly, the bite site will become firm and heal with little scaring over the next few days or weeks. Occasionally, the local reaction will be more severe with erythema and blistering, sometimes leading to a blue discoloration, and ultimately leading to a necrotic lesion and scarring. Signs that may be present include:

  • blistering (common),
  • necrosis (death) of skin and subcutaneous fat (less common), and
  • severe destructive necrotic lesions with deep wide borders (rare).


Should I see a doctor if I’ve been bitten by a brown recluse?

If you think you or someone you know has been bitten by a brown recluse spider, then the individual should be seen by a doctor that day. If possible, bring the spider in question to the doctor’s office. Identification of the spider is very helpful in making the correct diagnosis.

If the patient is unable to be seen by a doctor that day, he or she should seek care at a hospital’s emergency department.

How is a brown recluse spider bite diagnosed?

The doctor will try to make the correct diagnosis. It helps if the patient is able to produce the spider in question. That can often be difficult, because most victims don’t even realize they have been bitten before developing symptoms.

  • The doctor will ask about the bite event, time elapsed since the bite, other medical problems, medications, and allergies.
  • In general, laboratory tests are not necessary if the symptoms are localized to the area of the bites. If symptoms are more severe or seem to spread, laboratory studies that may be performed include complete blood count, electrolytes, kidney function studies, blood clotting studies, and urinalysis.
  • Although an immunologic (ELISA based) test for brown recluse spider bite has been developed, it is not commercially available or in routine use, therefore currently no specific lab findings can routinely confirm a brown recluse bite. Therefore, a presumptive diagnosis can occur only after a careful history and examination taking into account the likelihood of a bite depending on the part of the country where the person was bitten. This diagnosis can be confirmed if the spider is available and identified as a brown recluse.
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Are there home remedies for a brown recluse spider bite?

Home first aid care is simple. These self-care measures should not replace a visit to a doctor or emergency department.

After a spider bite:

  • Apply ice to decrease pain and swelling.
  • Elevate area if possible above the level of the heart.
  • Wash the area thoroughly with cool water and mild soap.
  • Avoid any strenuous activity because this can spread the spider’s venom in the skin.
  • Use acetaminophen (Tylenol) for pain relief.

Do not perform any of the following techniques:

  • Do not apply any heat to the area. This will accelerate tissue destruction.
  • Do not apply any steroid creams to the area such as hydrocortisone cream.
  • Do not attempt to remove the spider venom with suction devices or cut out the affected tissue.
  • Do not apply electricity to the area. Anecdotal reports of high voltage electrotherapy from common stun guns have never been shown to be effective in any scientific studies. This can also cause secondary burns and deepen tissue destruction.
  • Do not apply a tourniquet to the extremity involved.

What is the treatment for brown recluse spider bites?

After initial evaluation, the doctor may provide the following treatment:

  • Tetanusimmunization
  • Pain medication
  • Antibiotics if signs of infection are present in the wound
  • Antihistamines such as diphenhydramine (Benadryl) for itch relief

There is no antivenom available in the United States to counteract the poisonous venom of the brown recluse spider. Controversial therapies include steroids and the drug dapsone (Avlosulfon). These are often reserved for people with severe systemic disease (such as certain types of anemia, blood clotting problems, and kidney failure). The therapies have little proven benefit.

The patient will need to follow-up with a doctor because most wounds will need to be checked daily for at least three to four days. Necrotic lesions will need close follow-up. The doctor may carefully remove dead tissue in necrotic areas to reduce the chance of developing secondary bacterial infections.


What is the follow-up for a brown recluse follow-up?

After the initial evaluation by a doctor, the patient may expect this type of follow-up:

  • Daily follow-up of wounds for the first 96 hours to assess the possibility or extent of necrosis (tissue death) of wound
  • Hospitalization for people with systemic disease
  • Continuation of antibiotics until secondary infections clear
  • Follow-up with a surgeon if necrosis of the wound is evident

How do I prevent a brown recluse spider bite?

Reducing the possibility of an encounter with a brown recluse spider starts with eliminating known spider habitats.

  • Perform routine, thorough house cleaning.
  • Reduce clutter in garages, attics, and basements.
  • Move all firewood, building materials, and debris away from the home’s foundation.
  • Install tight-fitting window screens and door sweeps.
  • Clean behind outside home shutters.
  • Consider installing yellow or sodium vapor light bulbs outside entrances because these lights are less attractive to insects and draw fewer spiders to the area.
  • Consider professional pest elimination.

What is the prognosis for a brown recluse spider bite?

The majority of brown recluse bites cause little permanent skin damage, although, in some cases, moderate to severe tissue destruction is possible. The full extent of damage to tissues is not known for days. It may take many months for the wound to completely heal.

  • Brown recluse bites are noted for somewhat slow development of signs and symptoms, and often take up to 12 hours to reveal themselves. Necrosis of skin (death of skin), if it occurs, does so in the first 96 hours. Bites older than this that do not display tissue death have not been reported to worsen.
  • Necrotic lesions can be difficult to manage, and early surgery to remove dead tissue has not been shown to improve outcomes. Necrotic lesions with careful cleaning are allowed to mature for weeks until spreading stops and healing appears to begin. Then a wide area of tissue around the wound is removed and skin grafting may be done once all evidence of skin necrosis has subsided.

What does a brown recluse look like?


Pictures of Brown Recluse Spider Bite First Nine Days

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Medically reviewed by Avrom Simon, MD; Board Certified Preventative Medicine with Subspecialty in Occupational Medicine

Vetter R.S. and Bush S.P.. 2002 reports of presumptive brown recluse spider spider bites reinforce improbable diagnosis in regions of North America where the spider is endemic. Clinical infectious Disease 35:442-445

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