How to Identify a Spider Bite

Two Parts:Identifying Common Spider BitesDistinguishing from Other Insect Bites

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.[1] 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.[2] 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.

Part 1
Identifying Common Spider Bites

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    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.[3] 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.
    • Pay attention to more serious side effects such as 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.[4]
    • Anti-venom is available if the black widow bite causes severe pain and symptoms. It's 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 symptoms caused by the venom.
    • For identification purposes, the black widow spider is shiny, round and has a red diamond (or hourglass) shape on its underbelly. In the U.S., this spider is more common in the southern and western states.
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    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.[5] 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.[6] Medical attention is usually only needed if an ulcer forms and lasts for more than a few weeks.
    • In most cases the ulcer heals over with a scab and flakes off within a few weeks, but sometimes it can take many months for complete recovery if the victim's immune system isn't very strong — which is often the case in children and the elderly.
    • There is no anti-venom to help control the effects of a brown recluse spider bite. Its venom is classified as necrotizing, which means it kills the surrounding tissue and turns it black or blue.
    • To treat the wound, clean it with mild soap and water. Apply cold packs and elevate the area to reduce pain and inflammation.[7] Take over-the-counter pain relievers (acetaminophen) or anti-inflammatories (ibuprofen) as needed.
    • For identification purposes, brown recluse spiders are brown or yellowish. They have long spindly legs and a body with a head and oval abdomen. They're found in dark, quiet places in southern and Midwestern states.
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    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.[8] However, these "New World" tarantulas do throw or eject needle-like black hairs when agitated or threatened. The hairs lodge with skin and trigger an allergic-type reaction (anaphylaxis) involving hives, swelling and breathing difficulty, particularly in sensitized individuals. The initial pain is usually described as a stinging sensation.
    • Sensitized people are usually pet owners who handle their tarantula frequently.
    • Tarantula species native to Africa and the Middle East lack needle-like hairs, but they are more aggressive and produce venom.
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    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.[9] 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.[10]
    • 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.[11]

Part 2
Distinguishing from Other Insect Bites

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    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.[12] 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.[13]
    • 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.
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    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.[14]
    • 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 produces 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.
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    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.[15] 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 is 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.


  • To avoid spider bites, wear long-sleeved shirts, hats, gloves and boots when cleaning out garden sheds, garages, basements, attics and dark crawl spaces.[16] Remember to tuck cuffs of shirts and pants into gloves and socks to minimize points of entry for the insects.
  • Always inspect gardening gloves, boots and clothing that have been left unused for a while. Give them a good shake before putting them on.
  • Spraying insect repellent on clothing and footwear can deter spiders.
  • If you get a painful spider bite and are far away from medical help, ice the wound immediately. Then, treat the wound with antibacterial gel and other first aid supplies to keep it from getting infected.
  • Due to the many thousands of spider species in the world, be cautious when traveling abroad, particularly to countries in South America, Africa, Southeast Asia and Australia. Other potentially dangerous spiders of note around the world include the Brazilian wandering spider, funnel-web spiders, mouse spider, and red black spider.


  • Spiders can become infected with tetanus and pass it on when biting, so keep your tetanus boosters up-to-date — every 10 years.[17]

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Categories: Stings Bites and Burns