Brown Recluse Spider Bite: Symptoms, Diagnosis, Treatment

Brown recluse spiders live in the south-central United States. They prefer dark, enclosed spaces, such as attics, basements, cupboards, boxes, under rocks, and in the bark of dead trees.

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

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

Chris Vincent, MD, is board-certified in family medicine. He is a clinical professor at the University of Washington School of Medicine and practices at Harborview Medical Center in Seattle.

Table of Contents
Table of Contents

The brown recluse spider ( Loxosceles reclusa) is one of the most poisonous spiders in the United States. Their venom is necrotic, meaning that it destroys blood vessels, causing tissue near the site of the bite to die.

Getting bitten by one is uncommon and the bite alone rarely kills people. That said, severe reactions to a brown recluse spider bite can occur. If the reaction goes untreated, life-threatening complications may arise.

In the U.S., healthcare spending accounts for 17.7% of the Gross Domestic Product (GDP), or the total value of goods and services produced by the entire nation for the entire year, according to the Centers for Medicare & Medicaid Services.

This article details the signs and symptoms of a brown recluse bite and who’s at risk of being bitten. It also covers what you should do if you think you have been bitten by one of these spiders.

Where Are Brown Recluse Spiders Found?

Brown recluse spiders live in very specific parts of the south-central United States. The spiders are called “recluses” because they are hard to find even in the places where they live.

States With Brown Recluses

• Alabama
• Arkansas
• Georgia
• Illinois
• Indiana
• Iowa
• Kansas
• Kentucky
• Louisiana
• Mississippi
• Missouri
• Nebraska
• Ohio
• Oklahoma
• Tennessee
• Texas

Rare, isolated instances of brown recluses (such as by being brought into the state) have occurred in:

• Arizona
• California
• District of Columbia
• Florida
• North Carolina
• New Jersey
• Pennsylvania
• Washington
• Wyoming

In many cases, it’s thought that the spiders arrive in boxes and shipments that come from the states where they are native.

Brown recluses like dark, dingy places where they can hide under things. They are known to build their nests in attics, storage rooms, inside furniture and closets, and in other dry, dark, and warm spaces in homes and buildings. You may also find them under a woodpile outside.

Within their habitat, there can be serious infestations—if there is one brown recluse spider, there are most likely dozens or even hundreds more of them. However, even in homes with serious brown recluse infestations, it is unusual for people to get bitten.

They are nocturnal, so they are awake at night, and are more likely to run from you than strike. They will only bite out of self-defense.

Brown recluse spider bites are most likely to occur when the spider gets trapped against your skin. In many cases, the spider has crawled into a clothing item or a shoe and bites when you put the item on.

Identifying a Brown Recluse Spider

The only way to be sure that a bite came from a brown recluse spider is to see the spider bite you, capture it, and then definitively identify its type.

Most don’t even get the chance. Many people don’t even realize they’ve been bitten at first. It’s even rarer for a person to see the spider bite them and be able to catch it before it scurries off.

If you’re lucky enough to see the spider, here’s how to check for these telltale traits.

Look at the Legs

Brown recluses have legs that look different from other spiders. If you look at brown recluses from the side, you’ll see how the body sits low and the legs angle up to a point.

The angular, slanted leg shape gives brown recluses their scientific name (Loxosceles means “slanted legs”).

If a spider does not have this type of leg, it’s not a brown recluse. If it does, you can also check for other characteristics of brown recluses.

There are also two other features that set brown recluses apart from other species of spiders:

• No spines: Unlike many other spider species, Loxosceles do not have spikes or spines on their legs. The legs of brown recuses are smooth.
• Solid color: Some spiders have multicolored legs, but Loxosceles’ legs are solid. Brown recluses have no stripes and no patterns.

Check for Three Groups of Two Eyes

Another key feature to look for to identify brown recluses is the eyes. Brown recluse spiders have six eyes. The eyes are paired in groups of two ( dyads ). One dyad will be up front and the other two will be on either side of the head.

Other spider species might have eight eyes, or six eyes arranged in two triads (groups of three).

You cannot be sure a spider is a brown recluse based only on what the eyes look like. However, if the eyes are not in the proper pattern, then it’s definitely not a brown recluse.

Inspect the Body

Brown recluses also have specific features on their bodies that make them look different from other kinds of spiders.

• The body of a brown recluse (without legs) will be no more than 3/8 of an inch long. Including the legs, the average brown recluse is around the size of a quarter.
• The big round part on the backside of a brown recluse (abdomen) is a little fuzzy, has very fine hair, and is a solid color.

Find the Fiddle Marking

Brown recluses often have a violin-shaped mark on their back. However, not all brown recluses have it and even if it’s there, you might not be able to clearly see it.

There are also other spiders that also have the violin marking on their backs that are not brown recluses.

All of that said, identifying a brown recluse is difficult even for spider experts and doctors. Whether you think you’ve been bitten by a brown recluse or you’re unsure, seek medical attention if you notice a bite getting worse.

Brown Recluse Bite Symptoms

In 2014, only 1,330 brown recluse spider bites were recorded in the United States. Of these, 481 people required medical care.

Most brown recluse bites either don’t have any symptoms at all or there is a little swelling with a red bump. Some bites will develop a boil or a pimple that resembles an ingrown hair.

The bump might also be mistaken for a skin infection due to Staphylococcus or Streptococcus . At the same time, these bacteria can infect the spider bite wound.

When symptoms become severe enough to require medical care, it’s because the bite has become infected or caused what’s known as loxoscelism .

Signs of Infection

As is the case with any wound, a brown recluse spider bite can get infected if bacteria makes its way into the wound.

It’s always important to be on the lookout for signs of infection when you have a bite or wound of any kind.

Initial signs of infection include:

• Increased pain
• Swelling
• Warmth
• Redness in or around the bite

Loxoscelism

Necrotic arachnidism is a condition that can potentially occur when a person is bit by a spider that has venom that causes tissue to die.

When that spider is a brown recluse spider, the condition is referred to as loxoscelism. This is because the brown recluse belongs to a genus of spiders known as Loxosceles.

Loxoscelism only occurs in a minority of brown recluse spider bites. When it does, the effects are most often limited to the skin around the bite (local).

Local symptoms of loxoscelism due to a brown recluse spider bite include:

• Reddened skin around the bite
• A blister that forms at the bite site
• Mild to intense pain and itching for two to eight hours after the bite
• An open sore (ulcer) and tissue death that develops a week or more after the bite. The sore may take months to heal.

Complications

Untreated infection can lead to serious and possibly life-threatening complications, particularly:

• Cellulitis: A skin infection that has spread from the top layer of the skin into deeper layers
• Sepsis: Your body’s extreme response to infection in which chemicals in the blood trigger widespread inflammation throughout the body

Untreated sepsis can progress to septic shock, causing your blood pressure to drop dangerously low and your organs to start to shut down.

In the most severe cases of systemic loxoscelism, a person may develop:

• Hemolytic anemia: Red blood cells are destroyed faster than they can be made in your bone marrow, resulting in reduced oxygen delivery throughout the body and potential organ damage
• Thrombocytopenia : Low levels of platelets, blood cells that help form blood clots, which puts you at risk for excessive bleeding
• Kidney failure: The kidneys are injured by toxins in the venom, leading them to shut down and no longer be able to filter toxins and waste products from your blood

Systemic loxoscelism is a medical emergency. It’s rare, but if it is not treated, it can lead to death. Fortunately, very few deaths due to loxoscelism have been reported.

A 2017 study looked at loxoscelism cases ranging from 1995 through 2005. Of the 57 reported cases of moderate to severe loxoscelism, only two resulted in death. Both individuals—an older man and a young girl—were healthy prior to the bite.

It should also be noted that the study found 373 possible cases of loxoscelism over that 20-year period. The majority only led to minor symptoms that cleared up within a few weeks.

When to See a Healthcare Provider

It’s normal for any bug bite to leave a little redness and swelling around the bite site. It’s also normal for there to be some pain and itching.

If those are your only symptoms and they don’t get worse, you don’t need to see your healthcare provider. You should still watch the wound closely to make sure nothing changes in the hours or days after you are bitten, though.

Consult with a healthcare provider if the wound worsens or any of the following apply:

• The spider bite is on your face
• Your pain increases or is severe
• Redness spreads out from the wound
• Red or dark streaks extend from the wound
• A sore, boil, or ulcer forms at the bite site
• Pus or cloudy drainage oozes from the wound

In the case of a boil or ulcer, a healthcare provider may take a swab sample and culture it to test for bacteria. This will help them determine whether the wound is a spider bite or not.

Seeking Emergency Care

Any kind of systemic (body-wide) symptoms following a brown recluse bite should be treated as a medical emergency. This may indicate a progressing infection or loxoscelism.

Call 911 or go to the nearest emergency room if you develop any of the following:

• Fever or chills
• Widespread skin rash with many tiny, flat purple and red spots
• Nausea and vomiting
• Joint pain
• Trouble breathing
• Rapid heart rate
• Confusion
• Any other worrisome symptoms

In some cases, what a person thinks is a spider bite is actually another type of necrotic skin infection, such as necrotizing fasciitis. Skin infections like this can be much more dangerous than a spider bite.

Don’t hesitate to get medical care if you suspect infection or loxoscelism. Both conditions can rapidly get worse unless treated promptly.

Treatment

Most brown recluse bites heal just fine without any medical intervention. The first thing you should do for a new bug bite is wash it with mild soap and water.

From there, you can apply simple first aid to ease pain and swelling. The RICE method is recommended.

• Rest
• Ice
• Compression
• Elevation

Start by icing the bite area, taking care not to apply the ice directly to your skin. If possible, wrap the area with a compression bandage and then elevate it above the level of your heart.

Any time you place a bandage over a wound, make sure to remove it at least once per day to check for signs of developing infection. After removing the bandage, clean the wound with soap and water again, pat it dry, then re-dress it.

Over-the-Counter Medication

An over-the-counter anti-inflammatory medication, such as Advil (ibuprofen) or Aleve (naproxen) can also help reduce pain and swelling.

If you notice that the skin around the bite starts to look a bit red and swollen, wash the area with soap and water, pat it dry, then apply an over-the-counter antibiotic ointment. Keep a close eye on the wound for any increasing signs of infection.

Do not continue to self-treat your spider bite wound if it becomes infected or if a boil or ulcer develops. You will need more specialized treatment by a healthcare provider.

For Infection

You may be given a course of oral antibiotics if you have a mild case of cellulitis. If it’s severe, you will be given intravenous (IV) antibiotics in the hospital.

Should the infection progress to sepsis, you will need to be treated aggressively. You will need antibiotics right away and IV fluids to prevent dehydration.

If your blood pressure drops, you will be given a vasopressor medication, which constricts your blood vessels to raise blood pressure.

You will also be given supportive care based on your symptoms. That could once again include oxygen or a breathing machine. If your kidneys are affected, it could include dialysis.

In some cases, surgery may be needed to remove dead tissues or amputate a limb. This is a last resort (and an extremely rare one at that), but it will ensure the entire infection is gone.

For Loxoscelism

Treatment for local loxoscelism symptoms involves wound care and pain management. The healthcare provider will clean the wound and recommend that you use the RICE technique.

For pain relief, you may be given a nonsteroidal anti-inflammatory medication (NSAID) such as ibuprofen or naproxen. Very severe pain may be treated with an opioid, such as morphine.

You will be admitted to the hospital if you have signs of systemic loxoscelism. You will likely be given antibiotics and pain relievers.

You will then be given supportive care, which focuses on reducing your symptoms. For example, if your breathing is affected, you will be given oxygen therapy. If you develop hemolytic anemia, you may be given a blood transfusion.

The risk of life-threatening complications due to a brown recluse spider bite is very small, as are your chances of needing life-saving treatments for it. Nonetheless, you should monitor your spider bite closely to ensure that dangerous symptoms don’t have a chance to develop.

If you happen to know what bit you, let your healthcare provider know. There are no specific antidotes for brown recluse spider venom. But informing your provider will keep them more alert for specific loxoscelism symptoms, and help them to prepare treatment options in case symptoms develop.

Prevention

While you can’t always prevent a spider bite, you can take steps to lower your chances of being bitten.

Take note that brown recluse spiders are insect hunters. This means that they will seek out spaces where they can easily find crickets, cockroaches, and other bugs to eat.

If you live in a state where brown recluse spiders are found, you will want to protect your spaces from bugs that brown recluses feed on. Steps you can take include:

• Make sure that all your windows and doors are well-sealed.
• Keep your home clean and tidy.
• Keep your food sealed, limit where you eat, and don’t leave food lying around.
• Consider reaching out to a pest-control specialist if you can’t get rid of bugs on your own.

Keep in mind that brown recluses are most likely to bite if they feel trapped or provoked. Always shake out your clothing, blankets, and shoes before you use them.

Summary

If you’re in the south-central United States where brown recluse spiders live, you should be aware of what the spiders look like and where they prefer to nest.

If you get bitten and are able to trap the spider, bring it with you to see your healthcare provider. Clean the bite area with soap and water and watch it closely for changes. See a doctor if a boil or ulcers develop or if the wound gets hot, hard, or looks worse.

In rare instances, you may be at risk for loxoscelism, in which the skin around the bite begins to die away. Getting a diagnosis as soon as possible can ensure you have the right treatment to stop a potentially life-threatening problem.

Frequently Asked Questions

Where do brown recluse spiders live?

Brown recluse spiders live in the south-central United States. They prefer dark, enclosed spaces, such as attics, basements, cupboards, boxes, under rocks, and in the bark of dead trees.

What are the symptoms of a brown recluse spider bite?

Symptoms of a brown recluse spider bite include a rash, fever, nausea or vomiting, headache or body aches, and a black ulcer or blister at the bite location. Several hours or even days after the bite, the affected area can develop burning, itching, pain, and redness.

How do I treat a brown recluse spider bite?

• Wash the affected area with soap and water
• Wrap an ice pack in a towel and apply it to the area
• Apply an antibiotic lotion or cream to prevent infection.
• If the bite is on an arm or leg, use the RICE treatment (rest, ice, compression, elevation)

If the bite develops into a boil or ulcer, see a doctor right away.

Brown Recluse Spider Bite: Symptoms, Diagnosis, Treatment

A bite from a brown recluse spider can be mild or severe and may require medical attention. The toxins from this spider’s bite can cause tissue death.

Bites from the brown recluse spider almost never result in death but can cause serious skin damage, nausea, and muscle pain. With proper care, mild bites resolve within days to weeks, while more severe cases can take months to heal.

A bite from the brown recluse spider requires first aid, and if necessary, professional medical attention. Treatment often includes cleaning the affected skin, pain relievers, and icing.

Keep reading to learn the symptoms and stages of a brown recluse spider bite, how to identify the spider, and when to seek help.

What’s in the bite?

Even though this spider’s size maxes out at about a half-inch, its venom is more toxic than that of a rattlesnake. Luckily, the brown recluse is only capable of releasing a little into our system.

Here are two key toxins in the venom:

• Sphingomyelinase D has the potential to destroy skin tissues.
• Hyaluronidase can speed the venom’s penetration into tissue.

A brown recluse’s venom can destroy blood vessels, tissue, and nerves. As a result, the skin tissue can die, a phenomenon called skin necrosis.

In a 2020 study of 97 patients bitten by the spider, 40 percent experienced hemolysis, the damaging or breaking down of red blood cells.

Prompt treatment can slow these effects and allow your skin to begin healing faster.

Initial bite

Brown recluses have very small fangs, and their bite is usually painless. Unless you saw it happen, at first, you might not even be aware that a spider has bitten you.

You may start to notice a red, tender, and inflamed area about 2 to 8 hours after the spider bit you. Over the course of the next several hours, the irritation may cause a burning sensation.

The bite may appear as two tiny puncture holes . Early on, its center will be a pale color, with an inflamed reddish outer ring. The pain usually reaches its height at about the 24-hour mark after you are bitten.

After 3 to 5 days

In some people, the brown recluse’s venom is localized to only the area where the spider bit you. If the spider injected minimal venom and you’re healthy, the discomfort usually goes away in a few days.

But for others, the venom spreads. This causes the wound to expand, usually over a period of several days to weeks. Some people will develop a blister, and then a “necrotic lesion” due to the spider’s bite. This means the bite causes an ulcer or open sore, and tissue begins to die.

This may look like the following:

• dry, sinking patch of skin
• bluish-appearing patch of skin
• redness around the lesion with a pale center
• central blister

After 1 to 2 weeks

For mild bites, you should be mostly healed by 3 weeks or see a drastic reduction in inflammation.

But if you have a more severe bite, the spider’s toxin will continue to break down the skin, especially if untreated. The site of the wound may start to develop necrotic (dead) tissue called eschar. This looks like a big, black scab covering the wound area.

3 months later

Most brown recluse bites will heal fully, without complications, in 3 months or less.

In very rare cases where a lot of venom was delivered, necrosis in the wound can extend beyond the skin and into the muscles. If tissue death continues to occur or has already affected a large area, you’ll need to be evaluated by a surgeon. Surgery may be required to remove or repair excess dead tissue.

If the wound hasn’t responded to treatment or symptoms don’t align with the typical presentation of a brown recluse bite, it may be time for a differential diagnosis. Your doctor will consider other potential culprits of your symptoms, like another type of insect bite or a separate skin condition.

Severe reactions to a brown recluse spider bite

Some people have severe or life threatening reactions to brown recluse bites. These responses to the bite are more likely in those with compromised immune systems, including children and older adults.

Severe reactions to a brown recluse bite can include the following symptoms:

If you or a loved one is experiencing the above symptoms, seek emergency medical assistance. This may be a sign of anaphylactic shock, a life threatening allergic reaction.