Dangerous Spiders in Utah

Close-Up Of Spider On Field

 Maria Jeffs / EyeEm / Getty Images

Utah is home to three species of dangerous spiders. Use this information to learn about all three, plus find tips for spider bite safety and first aid.

Common sense measures for avoiding spider bites include reducing the number of spiders in the home, clearing away clutter, and wearing protective clothing around areas where spiders are likely to be. The Entomology Department at the University of California Riverside offers these tips for avoiding spider bites:

  • Use sticky traps to catch spiders. Every one you trap is one less spider that can bite you.
  • Remove bed skirts from beds and move the bed away from the wall. Remove everything from under the bed so that the only way the spiders can get on the bed is to crawl up one of the legs.
  • Many bites have occurred when people put on clothes that had been lying around and unknowingly pressed the spider against their skin. Don't throw clothes on the floor and then wear them the next day. If you do, shake them out. Bang out shoes first to see if a spider crawled in during the night.
  • When you store things in the garage, basement or attic, put them in sealable plastic bags. This is especially important for things that you stick your hands and feet into like: roller skates, baseball gloves, gardening gloves, boots, and rain gear. Tape up the edges of cardboard boxes.
  • Be careful when you move things out of storage areas, cardboard boxes, in particular. Spiders like to hang out in the space under folded cardboard flaps.
  • Clean up clutter. Spiders prefer to live under and between items.
  • Do not stack wood against the house. Move the woodpile as far from the house as possible, stack it off the ground, and cover it with a tarp. When you pick up wood, wear gloves.
01 of 04

Black Widow

Black widow spider
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Black widow spiders are found throughout North America, especially in the southern and western United States. Mature females are black and shiny, with a distinctive red hourglass marking on the underside of the abdomen. Immature spiders and males may be lighter or duller and may lack the red marking. Black widows can be found in crevices and undisturbed areas such as woodpiles, rock piles, under eaves, on fences, in outbuildings, and in areas where debris has accumulated.

In many cases, the bite of the black widow may cause nothing more than pain and swelling, and you may be able to see two small holes where the spider's fangs have pierced the skin. Individual reactions to spider venom vary, and sometimes spiders may "dry bite" to irritate an intruder without wasting venom.

In serious cases, severe symptoms will start to appear within 30 to 60 minutes. These include muscle cramps and spasms, vomiting, severe high blood pressure, stupor, or shock. ​

Call 911 immediately if the person bitten shows signs of shock or is having trouble breathing. 

  • Get medical help immediately. Call your doctor, hospital, or poison control center. The number for Utah Poison Control is 1-800-222-1222.
  • Remain calm. Too much excitement or movement will increase the flow of venom into the blood.
  • Apply ice to the bite area.
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02 of 04

Hobo Spider

Eratigena agrestis
Rainer Altenkamp, Berlin / Wikimedia Commons / CC BY-SA 3.0

Hobo spiders are common in the Pacific Northwest but have been known to live in Utah since the 1990s. The bite of the hobo spider is often misattributed to the brown recluse, which does not live in Utah. Both spiders can cause necrosis, or dying flesh, in the area of the bite.

Hobo Spiders build funnel-shaped webs in holes and crevices near the ground. They are not good climbers, but they are fast runners.

The Hobo is considered a dangerous spider, but severe bite cases have been difficult to document. Victims often do not see or catch the spider, and the necrotic lesions attributed to spider bites can be caused by other conditions. While the Centers for Disease Control have labeled the spider as dangerous, the hobo spider controversy continues on.

General information about hobo spider bite symptoms indicates you may not even know you have been bitten initially. Within a day or so, blisters may develop at the site of the bite and eventually rupture. Dead tissue from the area can slough off for as long as 45 days followed by healing and scaring.

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03 of 04

Desert Recluse

Desert Recluse
DesertTrip / Wikimedia Commons / CC BY-SA 4.0

The dangerous brown recluse spider ranges throughout the midwestern and southern United States but does not live in Utah. A related species, the desert recluse, can be found in the southwest United States, including the extreme southwest corner of Utah.

Like the hobo spider, the desert recluse and other recluse spider species are frequently blamed for necrotic lesions and skin infections that actually have other causes. The desert recluse and other recluse spiders are difficult for non-experts to identify.

According to ​​First Aid Expert Rod Brouhard, "Most brown recluse bites heal just fine without any medical intervention or first aid. If you see it happen or suspect that you were bitten, the recommended treatment is to use RICE (rest, ice, compression, and elevation). Wrap the area of the bite with a compression bandage, use ice on it, and elevate it. If the bite develops into a boil or an ulcer, see a doctor."

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04 of 04

Spider Bite First Aid

doctor bandaging
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Most spider bites heal on their own without treatment and only need basic first aid measures such as keeping the wound clean, bandaging, and watching for signs of infection. The main dangers of spider bites are allergy, systemic poisoning, and necrosis. First Aid expert, Rod Brouhard, offers this information about treating spider bites:


Anaphylaxis is always the biggest concern with any type of bug bite. If the victim exhibits any of these signs of allergic reaction or anaphylaxis shortly after a bug bite, call 911.

  • hives
  • shortness of breath
  • wheezing
  • weakness

Systemic Poisoning

Victims should seek medical treatment if symptoms appear in parts of the body away from the location of the bite. Black widow spiders have a toxin that affects muscle contraction and nerve function. Severe brown recluse spider bites can also cause some symptoms over the entire body (systemic reaction). Look for:

  • sweating
  • chills
  • headache
  • body aches
  • stomach cramps
  • leg cramps
  • rapid pulse
  • exhaustion

In cases where the victim is feeling extremely tired or weak, call 911.


Necrosis can be associated with hobo spider or desert recluse bites. Most bites heal just fine without any medical intervention or first aid. If you see it happen or suspect that you were bitten, the recommended treatment is to use RICE (rest, ice, compression, and elevation). Wrap the area of the bite with a compression bandage, use ice on it, and elevate it.

If the bite develops into a boil or an ulcer, see a doctor. This isn't typically 911 worthy, but you'll want to get a physician to take a look. One thing a doctor might do is take a swab from the boil and culture it (test for bacteria). That way, if it can be treated with antibiotics, it will be. Antibiotic treatments will only be effective if there is a bacterial infection. The necrosis associated with spider bites can take months to heal.

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