How to Identify a Spider Bite

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1 Identifying Common Spider Bites

2 Distinguishing from Other Insect Bites

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Co-authored by Anthony Stark, EMR

Last Updated: November 10, 2024 Fact Checked

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There are thousands of spider species in the U.S., but the vast majority of them have fangs that are either too short or too fragile to penetrate human skin. Even if you do get a spider bite, the chances of a fatal reaction are slim: only about three deaths a year in the U.S. are attributed to spider bites. However, spider bites can definitely hurt and sometimes lead to systemic reactions because of their venom. The two most dangerous species to worry about in the U.S. are the black widow spider and the brown recluse spider. Being able to identify their bites from other spiders and insects will allow you to gauge the degree of seriousness and whether you need to seek medical attention or not.

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Part 1

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Identifying Common Spider Bites

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1. 1
   Look for a two-fanged puncture wound. A bite from a black widow is often

   immediately painful

   and can be distinguished from other spider and insect bites by the

   two puncture marks

   it makes on the skin. Although it may be painless, usually a black widow bite is at least moderately painful because the spider has long, sharp fangs. The two-fanged puncture wound then starts to turn red, become inflamed and

   form a nodule.

   Tenderness at the bite site tends to increase and spread out within an hour.

   Black Widow Bite Quick Tips
   Bite shape: Two-fanged puncture wound.
   Typical reaction: Tenderness at the bite site, and then spreading pain within an hour. Wound turns into an inflamed nodule.
   Serious side effects: severe muscle cramping (especially in the abdomen), excessive sweating around the bite mark, nausea, headache, delirium, chills and high blood pressure. These are all reactions to the spider's neurotoxic venom.
   Anti-venom? Yes, it is available if the bite causes severe pain and symptoms. It’s usually injected into the thigh or given through a vein (intravenously) by a medical professional, although the anti-venom can cause serious allergic reactions that are worse than the venom symptoms.
   Identifying a black widow spider: The black widow spider is shiny, round and has a red diamond (or hourglass) shape on its abdomen.
   Location:Temperate regions, including the United States, Australia, South Africa, southern Europe, southern Asia, South America
2. 2
   Look for a "bull's eye" bite wound. A bite from a brown recluse spider is usually painless or causes a

   mild stinging sensation

   similar to a mosquito bite. Within about 30 – 60 minutes however, the bite area becomes red and inflamed with a central sore called a "bull’s eye" lesion. Redness and intense pain develop within eight hours as the central sore becomes larger, fills with blood, ruptures and then leaves a

   very tender ulcer.

   During this stage, a deep blue or purple area often forms around the bite, usually with a red ring around it. Medical attention is usually only needed if an ulcer forms and lasts for more than a few weeks.

   Brown Recluse Bite Quick Tips
   Bite shape: Bull’s eye.
   Typical reaction: Inflammation and redness within 30-60 minutes after bite. Intense pain over the next 8 hours as the sore fills with blood and ruptures, leaving a tender ulcer.
   Serious side effects: None, but it can take multiple months for the victim to fully recover if their immune system is weak. This is often the case with children and the elderly
   Treatment:Clean the wound with mild soap and water. Apply cold packs and elevate the area to reduce pain and inflammation. Take over-the-counter pain relievers (acetaminophen) or anti-inflammatories (ibuprofen) as needed. Usually, the ulcer will scab over and flake off within a few weeks.
   Anti-venom? No, there is no anti-venom. Brown recluse venom is necrotizing, meaning that it kills the surrounding tissue and turns it black or blue.
   Identifying a brown recluse spider: brown recluse spiders are brown or yellowish. They have long spindly legs and a body with a head and oval abdomen. They commonly have a violin-shaped spot on their head.
   Location:Southern and Midwestern United States

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3. 3
   Watch for needle-like hairs in your skin. Although tarantulas are arguably some of the most scary looking spiders, the types native to North and South America are not venomous and rarely ever bite. However, these "New World" tarantulas do throw or eject needle-like black hairs when agitated or threatened. Note that tarantula species native to Africa and the Middle East lack needle-like hairs, but they are more aggressive and produce venom.

   Tarantula Hair Quick Tips
   What it looks like: Little needle-like hairs lodged in your skin
   Typical reaction: Initial stinging sensation.
   Serious side effects: Anaphylaxis, which brings hives, swelling, and breathing difficulty
   Treatment: For anaphylaxis, epinephrine pen injection.
   Location: Southwestern United States, South and Central America
4. 4
   Identify other spider bites. The bites from black widow and brown recluse spiders are most identifiable, mostly due to the fact that they have the most potent venom and typically cause the most symptoms. However, other spider bites are more common and can lead to pain and swelling also. For example, the Hobo is a large, fast-running spider with yellow markings on its brown back. They inject neurotoxic venom when they bite people that can cause some surrounding skin to die, but not nearly to the extent that brown recluse venom does.

   • Bites from Hobo and Sac spiders cause discomfort and wounds that mimic a bee or wasp sting, although the initial pain is much less because the fangs of these spiders are not nearly as large or strong as bees / wasps.
   • To help identify the type of spider bite you have,
     capture the spider or take a photo with your phone
     and take it to a local clinic (someone might be able to identify it) or research it online. Most spider bites or harmless or cause only mild discomfort that fades away after a few days.
   • Treating spider bites with antiseptic gel, ice and over-the-counter medications is typically all that's needed.
   • Generally speaking, spiders bite only in defense, particularly while being crushed between your skin and something else.
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Distinguishing from Other Insect Bites

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1. 1
   Remember that many insect bites are more painful than spider bites. Spider bites are often falsely suspected by patients because they assume that spiders can do more damage than what they're actually capable of. For example, insects such as bees and wasps use powerful stingers to inflict skin wounds, which does much more initial damage than the small fangs of spiders. A bee leaves its stinger in the skin and then dies shortly thereafter, whereas wasps (including hornets and yellow jackets) can sting you repeatedly.

   • Reaction to bee and wasp stings can range from minor skin swelling and redness (like a small contusion or bruise) to a serious allergic reaction (anaphylaxis) in those who are sensitive — medical attention may be necessary. Bees and wasps don't inject venom but kill many more people per year than spiders due to anaphylaxis reactions that go untreated.
   • Anaphylaxis is usually controlled by epinephrine (adrenaline) injections
     that reduce the body's allergic response. An injection can be given by your doctor or administered at home if you have an epinephrine "pen".
   • The type of spider bites most often confused with bee / wasp stings are from Hobo and Sac spiders. Black widow bites can cause similar serious symptoms, but their two-fanged puncture wound doesn't resemble a bee / wasp sting.
2. 2
   Watch for painful scorpion stings. Although scorpions have crab-like pincers, they sting with their tail instead of pinching or biting. Scorpion stings are usually painful and cause localized redness and inflammation, but they are rarely serious and usually don't need medical attention. However, the

   bark scorpion can inflict potentially fatal stings

   because it produces a potent neurotoxic venom.

   • Although the sting marks of scorpions look much different than the two-fanged puncture wounds of black widows, the pain and other symptoms can be quite similar because both species produce neurotoxic venom.
   • An antivenin (Anascorp) is available, but it's not used widely in the U.S. due to America's low mortality rates.
   • Much like most spider bites, the vast majority of scorpion stings can be treated with antiseptic gel, ice, and over-the-counter medications.
   • The bark scorpion is native to Arizona, New Mexico and parts of California.
3. 3
   Don't confuse tick bites as spider bites. Tick bites are sometimes confused as brown recluse spider bites (and vice versa) because they can also produce a skin reaction that looks like a bull's eye. Some

   ticks (such as deer ticks) may carry Lyme disease

   , so they shouldn't be taken lightly. Symptoms from a tick bite that carries Lyme disease include a skin rash in concentric rings, which appears up to a month later, as well as fever, fatigue, headaches, and aches in muscles and joints.

   • The main differences from a brown recluse spider bite are that tick bites don't initially hurt and never lead to ulceration (necrosis) of the skin surrounding the bite.
   • Another difference is that ticks usually burrow into the skin before infecting the host, so you can sometimes see them underneath the top layer of skin. In contrast, spiders don't burrow or nest in or on people.
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Tips

• To avoid spider bites, wear long-sleeved shirts, hats, gloves and boots when cleaning out garden sheds, garages, basements, attics and dark crawl spaces. Remember to tuck cuffs of shirts and pants into gloves and socks to minimize points of entry for the insects.
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• Always inspect gardening gloves, boots and clothing that have been left unused for a while. Give them a good shake before putting them on.
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• Spraying insect repellent on clothing and footwear can deter spiders.
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Warning

• Spiders can become infected with tetanus and pass it on when biting, so keep your tetanus boosters up-to-date — every 10 years.