Spider Bite Pictures: Appearance and Emergency Signs

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.

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.

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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.

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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.

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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:

• Numerous bites
• Occurrence
• Timing
• Red center
• Elevated
• Chronic
• Large
• Ulcerates too early
• Swelling
• Exudes pus or blood

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.

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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.

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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.

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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.

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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.

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.

If a brown recluse bite grows in size and becomes painful, your healthcare provider may prescribe antibiotics to prevent infection. If it is unclear that you've been bitten by a brown recluse, a tetanus shot may be given as a precaution, particularly if you haven't had one in the past five years.

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.