What You Think Is A Spider Bite Is Usually Something Else Entirely, Doctors Say (2023)

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First, how can you be sure it's a spider bite?

Sometimes, spiders leave behind two distinct puncture holes right next to each other. But unless you actually see the spider do the dirty deed, it's hard to know if it was caused by an arachnid or some other bug.

In fact, the vast majority of "spider bites" are actually bites from other insects like fleas, ticks, and mosquitoes, a rash from an allergic reaction, or skin abscesses from an infection, says Justin Arnold, DO, MPH, an assistant professor at the University of South Florida and the medical director of the Florida Poison Information Center Tampa.

The symptoms are often similar too—pain, swelling, itching, and redness—so it's an easy mistake to make. In fact, even spider experts and medical professionals have a hard time differentiating bug bites from spider bites just from how they look, Dr. Arnold adds.

"Many people don’t recall an injury or specific bite and hold a common belief that a spider must have bitten them without them knowing," he says. "In a majority of the cases that we see, a spider was never seen by patient and is not responsible for their infection."

It’s also important to know what to look for in darker skin tones, says Rajani Katta, MD, a board-certified dermatologist who serves as voluntary clinical faculty of both the Baylor College of Medicine and the McGovern Medical School, University of Texas Houston.

“For myself, and my patients with more deeply pigmented skin, the redness from an insect bite can be more subtle," she explains. "Instead of a bright red color, I'll often see more of a faint redness, or a reddish-brown color."

If she is worried about a more serious spider bite, Dr. Katta will often mark the boundaries of the rash around the bite, and then check those boundaries on a daily basis.

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So, what happens when a spider bite becomes infected?

While poisonous bites are rare, any bite—spider or otherwise—can turn serious if it becomes infected, says Dr. Arnold. There are three main complications that can arise from bites: cellulitis, blisters, and swelling.

When a spider bite turns into cellulitis—a common (and painful) skin infection—a rash begins to spread around the wound, and the skin becomes painful and hot to the touch.

Another common reaction to many spider bites is "weeping" blisters at the site (they look puffy and fluid-filled). Small blisters on their own, with no other symptoms, don't necessarily need special care. But if a blister opens, it becomes at risk for infection, says Dr. Arnold, so don't try to pop them! If you think you may have an infection at the bite site, whether from cellulitis or open blisters, it's best to have your doctor take a look.

Swelling is another very common symptom of insect or spider bites. Even though the swelling can get quite pronounced, it's not necessarily a problem, as long as it goes down within a few days. But if the swelling doesn't go down, gets significantly worse, or is accompanied by other symptoms, it's time to get medical attention, says Dr. Arnold.

Actually feeling the skin around the bite becomes more important for BIPOC patients in particular because severe swelling can be a sign of a more worrisome spider bite, says Dr. Katta. Another concerning sign that BIPOC patients should watch out for is necrosis, in which the skin at the site of the bite starts to die off. When this happens, you may see a central ulcer with a black crust.

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What do jumping spider And wolf spider​ bites look like?

The two most common spider bites are from house spiders, specifically the jumping spider and wolf spider. While it can be scary to be bitten by any spider, these bites normally aren't any more painful than a bee sting and shouldn't cause problems beyond some redness, swelling, and itching, Dr. Arnold says.

Treat these at home by washing the site with soap and water, using cold compresses, and taking an ibuprofen to reduce pain and swelling, he adds.

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What do black widow spider bites look like?

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Of all of the spiders, black widows pose the greatest health threat to Americans, according to Rick Vetter, PhD, a spider expert in the department of entomology at the University of California, Riverside. Their bite is extremely painful and, while an antivenin (a.k.a. anti-venom, or an injection given to boost antibodies against a particular poison) exists now, before it was discovered, about five percent of bitten people died.

Think you can ID a black widow bite on sight? Not so fast: The actual bite looks a lot like any other spider bite. However, they do tend to become more swollen and redder than your general household spider bite, Vetter says.

Black widow spiders are tough to identify as well. Only female black widows have the characteristic red hourglass-shaped markings on their backs. Male and immature black widows have tan and white stripes, according to Vetter.

Because these types of bites are so serious, if you strongly suspect you were bitten by a black widow spider or you develop muscle cramping, abdominal and chest pain, high blood pressure, a racing heart, and/or vomiting within two hours of a bite, go to the ER immediately, Dr. Arnold says.

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What do brown recluse spider bites look like?

The brown recluse spider (also known as the fiddleback spider or violin spider) is one of the most venomous spiders in America, but they are limited to very specific geographic regions—if you don't live in one of these places, it's highly unlikely you need to worry about this type of bite, Vetter says. (Check out this map to see if you're in the danger zone.)

And despite what you may have heard, even where brown recluses are present, they rarely bite, he adds. To identify a brown recluse, look for six eyes arranged in pairs. (Although getting close enough to see the eye pattern on a spider sounds, frankly, terrifying.)

Brown recluse bites do happen though, and when they do, they are often accompanied by "sharp, burning pain," Dr. Arnold explains. Within several hours, the bite area becomes discolored and forms an ulcer that can takes several weeks to heal. In addition to the wound, individuals can also develop fevers, muscle aches, and in rare cases, severe anemia as a result of the venom.

Start by treating any bite at home with cold compresses and an antibiotic cream, but if you start to show severe symptoms, including a lot of swelling, increased pain, fever, spreading rash or other sign of infection, seek medical attention immediately. There isn't an antivenin, but a doctor can treat the symptoms and manage the infection.

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What do hobo spider bites look like?

The hobo spider is actually a pretty common venomous house spider in the U.S., but despite some scary media reports, they're not aggressive and will only bite if provoked, according to the U.S. Forest Service. In addition, about half of hobo spider bites are "dry," meaning they contain no venom, the service adds.

If you do receive a venomous bite, within a few hours it will become red and hard, similar to a mosquito bite, and within a day or two you will develop blisters. After the blisters open, a scab typically forms along with a rash that often looks like a target or bull's eye.

Because these wounds can become necrotic and last for years in some cases, you should see a doctor immediately, Dr. Arnold says. There isn't an antivenin, but they can treat the symptoms and manage any infection with antibiotics.

Hobo spiders can be hard to identify, according to the Forest Service. They are large and often have chevron-type markings on their backs, but these won't be visible on darker-skinned adult spiders, which is why it's important to get any bite checked out if it starts to show signs of infection or you see a target forming on your skin, Dr. Arnold says.

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What do tarantula bites look like?

Tarantulas may look big and scary, but most of the North American varieties are pretty chill. And even while the bite itself can be painful, the venom is fairly benign and likely won't cause long-term issues, Dr. Arnold says. Like most spider bites, tarantula bites can cause some swelling, itching, and irritation.

However, he adds, tarantulas also have the ability to flick hairs off of their body and into your skin, which can be very irritating and painful. And some people are allergic to tarantula venom, which can make the bite even more inflamed, according to the National Institutes of Medicine.

Most of the time, it's fine to try treating these at home by washing the site, applying ice, and taking ibuprofen, Dr. Arnold says. But if you find yourself having a more extreme reaction, including symptoms like a rapid heart rate or difficulty breathing, get to the emergency room.

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So, how do you treat a spider bite?

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If you are bitten by a spider, you should immediately wash and clean the skin, says Joshua Zeichner, MD, the director of cosmetic and clinical research and an associate professor of dermatology at Mount Sinai Hospital in New York City. “You should thoroughly cleanse the skin, but avoid over-scrubbing or using a harsh soap that can disrupt the skin barrier. The Dove beauty bar is my go-to,” he says.

Next, apply a cool compress to the skin for 15 minutes to reduce inflammation and an over-the-counter anti-itch cream to limit irritation. An OTC allergy medicine like Benadryl, Claritin, Allegra, or Zyrtec may also help. “Taking an antihistamine will reduce the allergic reaction from the inside out,” he says.

Oral and topical OTC treatments will usually help cut down on recovery time, minimize any discomfort, and heal the bite within a week, but if you develop a rapidly growing skin rash or have difficulty breathing, you should go to the emergency room ASAP, stresses Dr. Zeichner. These types of bites are rare, but brown recluse, black widow, and hobo spider bites can be deadly, so if you suspect one bit you, seek medical treatment immediately. You may need antibiotics, prescription pain relievers, or antivenin in the case of a black widow.

And yes, it can be very difficult to know, find, and catch the exact spider that bit you, but if you spot the creepy crawler, try to *safely* capture and bring it to a doctor. “A diagnosis of a spider bite is most often based on the history and clinical presentation, but if the spider can be identified, it would allow for a more definitive diagnosis and treatment plan,” says Dr. Chaudhari.