A Guide to Venomous Spiders That Bite Humans in the U.S.

Spiders That Bite Humans

While the majority of spiders in the world are harmless to humans, there are a few spider species with venom capable of causing injury. Spider bites are uncommon, but it's good to know how to identify spiders that pose a danger and what to do if you get bitten.

This guide covers spiders that bite humans, how to recognize them, where they live, whether they are found in your state, first aid for bites, and when to seek medical care. Learning to coexist safely with our arachnid neighbors is key.

Brown Recluse Spiders

One of the most feared spiders in North America is the brown recluse spider. Despite their shy, reclusive nature, brown recluse spiders do occasionally bite people. Their venom can cause significant skin damage in some cases.

Identification

Brown recluse spiders are usually light to medium brown in color with a dark brown violin shape on the cephalothorax (the front body section). They have six equal sized eyes arranged in pairs, with a legspan around 1 inch long.

Range

Brown recluse spiders are primarily found in the central Midwestern states like Missouri, Kansas, Oklahoma, Texas, and Arkansas. Isolated populations also occur in other states like Florida, Georgia, Ohio, and Indiana.

Bites

Bites occur when spiders get accidentally trapped against human skin. Most bites happen in the summer months. The venom causes localized tissue damage, resulting in swelling and a painful lesion called a necrotic ulcer that takes weeks to months to heal.

First Aid

Clean the bite area with soap and water. Apply a cool compress to relieve swelling. Seek medical care if a blister forms or spreads.

Do They Live in Utah?

There are no known established populations of brown recluse spiders in Utah. However, isolated spider sightings have occurred rarely, likely from accidental transport in vehicles or belongings from endemic states.

Black Widow Spiders

Black widow spiders have a notorious reputation due to the neurotoxic venom of the female that can cause severe muscle pain and abdominal cramping in humans. These shiny black spiders with a red hourglass shape on the abdomen are found throughout much of North America.

Identification

Female black widows are jet black in color with a reddish hourglass marking on the belly. Males are smaller, brownish, with light striping. Legspan is around 1.5 inches.

Range

Black widows live in warmer areas across the southern, central, and western United States, stretching up into Canada. They favor secluded, dry outdoor areas with abandoned rodent burrows and woodpiles.

Bites

Bites occur when spiders get trapped against skin inside clothes or shoes. The neurotoxic venom can cause muscle rigidity, cramping, nausea, and difficulty breathing in severe cases.

First Aid

Clean bite, apply ice pack, and take pain relievers. Seek emergency care for significant symptoms like abdominal pain, chest tightness, or breathing issues.

Do They Live in Utah?

Yes, black widow spiders are found throughout Utah, especially in drier areas below 5,500 feet elevation around woodpiles, sheds, garages, and abandoned rodent burrows.

Hobo Spiders

Hobo spiders are common fast-moving spiders in the Northwestern United States. They occasionally wander indoors and have a toxic venom that can damage skin tissue.

Identification

Hobo spiders have an elongated body up to 14mm long. They are brownish in color with faint striping on the cephalothorax and abdomen.

Range

Hobo spiders are primarily found in the Pacific Northwest states of Oregon, Washington, Idaho, and Western Montana. They live outdoors but frequently come inside houses and buildings.

Bites

Most hobo spider bites occur when spiders get trapped against skin in clothes, bedding, or towels. The venom can destroy skin cells, causing a slow-healing open wound.

First Aid

Wash bite area, apply ice, elevate limb. Seek medical care if wound does not improve. Antibiotics may help prevent infection.

Do They Live in Utah?

No, hobo spiders are not found in Utah. They mainly reside in the moist forests of the Pacific Northwest region.

Wolf Spiders

Wolf spiders are large, hairy spiders common across the United States. They have a moderately toxic venom that poses little threat to humans.

Identification

Wolf spiders come in a range of brown colors and often have stripes on their bodies. They have eight eyes arranged in three rows. Legspan reaches up to 5 inches.

Range

Hundreds of wolf spider species exist nationwide. They live outdoors and under debris in fields, forests, and gardens across the continental US.

Bites

Bites can occur when trapped against skin. The venom causes mild pain and swelling. Serious reactions are rare but may include nausea, headache, and cramping.

First Aid

Cleanse bite, apply compresses, and monitor for infection. Take OTC pain medication as needed for symptoms.

Do They Live in Utah?

Yes, several harmless wolf spider species are found throughout Utah. They reside outdoors under rocks, woodpiles, vegetation, and other protected areas.

Fiddleback Spiders

Fiddleback spiders, also called brown or recluse spiders, have six eyes instead of eight like most spiders. Their violin-shaped marking gives them a mildly toxic venom.

Identification

Fiddlebacks are brown with a distinctive fiddle-like pattern on the cephalothorax. They have six eyes instead of the usual eight. Legs span around 2 inches wide.

Range

Primarily located in the southwestern states of Arizona, New Mexico, Texas, California. They like warm, dry, secluded shelter outdoors.

Bites

Fairly uncommon. Mild reaction includes redness, swelling, and itching at the bite site. Heals on its own in 1-2 weeks.

First Aid

Clean bite, apply ice, take OTC pain medication. Monitor for infection. Seek medical care if severe swelling develops.

Do They Live in Utah?

No, fiddleback spiders are not found in the state of Utah. Their range is limited to states in the southwestern United States.

Sac Spiders

Sac spiders have a venom that sometimes causes skin lesions in humans. They get their name from the silken tube-shaped retreats they build for shelter.

Identification

Light brown or grey coloring, small legs, greenish jaws. Look for their tubular sac retreats in corners, crevices, or foliage.

Range

Common across much of the United States in gardens, woodlands, farms, and human structures. They come indoors in fall seeking shelter.

Bites

Uncommon and painless. The venom destroys skin cells causing an itchy, inflamed lesion that slowly heals over several weeks.

First Aid

Wash bite, apply antibiotic cream. See doctor if wound does not improve with topical treatment. Oral antibiotics may help.

Do They Live in Utah?

Yes, sac spiders are found throughout Utah, especially in man-made structures. They wander indoors in autumn when seeking shelter from the cold.

Cellar Spiders

Also called daddy longlegs spiders, cellar spiders have tiny bodies and long, spindly legs. They are common residents of homes where they prey on other spiders.

Identification

Extremely long legs, small body, gray to brown coloring, and prone to vibrating up and down when disturbed.

Range

Cellar spiders reside in structures across North America as well as outdoors under rocks and vegetation. They prefer dark corners and ceilings.

Bites

Extremely rare since they can't easily pierce human skin. No venom of significance to humans.

First Aid

Wash area with soap and water if bitten. Apply antiseptic ointment and pain relief medication if needed.

Do They Live in Utah?

Yes, harmless cellar spiders are very common in Utah homes, garages, and basements where they consume other household spiders.

Spider Bite Symptoms

Most spider bites are harmless, but some venomous spiders can cause varying degrees of pain, skin damage, and illness. Here are some common spider bite symptoms:

Pain

Sharp stinging or throbbing pain at the bite site immediately or within minutes of being bitten. Pain intensity depends on the type of spider and amount of venom injected.

Redness and Swelling

Reddening, inflammation, and swelling around the bite. Can spread and increase in size over hours as the venom takes effect.

Itching

Itchy skin around the spider bite is common. This may continue during the healing process due to inflammation and tissue damage.

Skin Lesions

Some spider bites cause blistering, ulcers, or dead tissue at the bite site due to venom components that destroy skin cells and tissue.

Nausea and Vomiting

Feeling sick, queasy, or vomiting can result from the pain of a serious spider bite or toxins in the venom entering the bloodstream.

Headache

Venom toxins circulating through the blood can lead to headache, especially with black widow spider bites.

Muscle Cramps

Particularly with black widow spiders, the venom can cause painful cramping of the abdominal and limb muscles.

Weakness and Fatigue

In some cases, spider venom leads to exhaustion, weakness, tremors, and dizziness from the effects of the toxins.

Seek prompt medical attention if bitten by a suspected dangerous spider, especially if symptoms are severe or progressing rapidly. Most spider bites can be effectively treated.

First Aid for Spider Bites

If you are bitten by a spider, take these immediate first aid steps while monitoring for symptoms:

Wash the Bite

Use soap and water to gently cleanse the bite area and remove any venom on the surface of the skin. Do not scrub harshly.

Apply a Cool Compress

Place an ice pack, cool cloth, or water-soaked gauze over the bite to help reduce pain and swelling.

Elevate the Bitten Limb

If bitten on an arm or leg, keep it raised above heart level to slow venom spreading through the bloodstream.

Take OTC Pain Medication

Ibuprofen, acetaminophen, or aspirin can help relieve symptoms like pain and headache caused by the venom.

Avoid Tight Bandages

Wrapping the bite too tightly can cut off circulation and increase damage. Lightly secure gauze over it instead.

Watch for Worsening Symptoms

Monitor for signs of progression like spreading redness and swelling, nausea, cramping, or difficulty breathing.

Get Medical Care If Needed

Seek emergency care if symptoms are severe or get rapidly worse, especially with known venomous spiders.

Taking quick action helps limit venom exposure and complications. But severe spider bites still require medical treatment so always seek evaluation.

How to Avoid Spider Bites

You can reduce your chances of being bitten using these spider bite prevention tips:

Reduce Clutter

Spiders nest in piles of debris and stored items outdoors and indoors. Keep areas tidy.

Wear Protective Clothing

When cleaning dusty or cluttered spaces, wear gloves, long sleeves and pants to keep skin covered.

Shake Out Items

Spiders may hide in clothing, shoes, towels, and bedding. Thoroughly shake out and inspect items before use.

Install Screens

Well-fitting screens on windows and doors help keep spiders out of your home.

Apply Insecticides

Carefully using pesticides around the perimeter of your home helps deter spiders and other pests.

Inspect Play Areas

Check for spiders under toys, structures, and sandboxes where children play outside.

Clear Webs

Regularly knock down webs on porches, eaves, garages, and fences to keep spider numbers down.

Get Rid of Spider Shelters

Remove woodpiles, rocks, thick vegetation, rodent burrows, and other hiding spots spiders utilize.

Practicing proactive prevention helps make your home and yard less inviting to spiders that could bite. But always be vigilant when cleaning gardens and structures.

When to Seek Medical Care for a Spider Bite

Most spider bites can be treated at home with first aid and close monitoring. However, seek prompt medical evaluation if you experience:

• Severe pain at the bite site
• Rapid swelling extending past the bite
• Blistering, oozing, or ulcers at the wound
• Red streaking away from the bite
• Muscle cramping, rigid abdomen
• Nausea, vomiting, or difficulty breathing
• Feeling ill or flu-like
• Persistent headache
• Skin damage that progresses after 48 hours

Go to an emergency room or urgent care right away if bitten by a black widow or brown recluse spider, as specific antivenom treatment may be needed.

Seek medical advice anytime a spider bite causes concerning symptoms or seems to worsen despite home treatment. Bites on fingers, toes, the face, or genitals should also receive prompt medical care.

Let a doctor assess your symptoms and decide if prescription antibiotics or other interventions are warranted for proper healing and infection prevention.

While most spiders do not inflict serious bites, their venom can occasionally cause severe reactions or skin damage. Seeking timely medical treatment provides the best outcome if bitten by a spider.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.