Carrie Madormo, RN, MPH, is a freelance health writer with over a decade of experience working as a registered nurse in a variety of clinical settings.
Keri Peterson, MD, is board-certified in internal medicine and has her own private practice on the Upper East Side of Manhattan. She holds appointments at Lenox Hill Hospital and Mount Sinai Medical Center.
Spider bites are usually harmless but can lead to pain, redness, and swelling.
Occasionally, a spider bite may cause an allergic reaction. Bites from black widows and brown recluse spiders are dangerous because they are poisonous.
This article will describe different types of spider bites, how to treat them, and when to see a healthcare provider.
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Most spider bites are harmless and share the same symptoms as a bee sting, including pain, redness, and swelling. All spiders make venom but most of them have fangs that are too small to puncture the skin. This is why most bites do not cause serious symptoms.
Venomous spiders in the United States include the brown recluse and black widow. They normally only bite if they feel trapped or have been touched.
The brown recluse spider is known as the violin spider because of the violin-shaped mark on its back. It is about 1 inch long. While most spiders have eight eyes, the brown recluse has six.
Brown recluse spiders are commonly found in the Midwest and the South in the United States. They usually live in dry, secluded areas like underneath log piles or in rocks and leaves. Indoors, they may be found in dark areas of the house like closets or the attic.
A brown recluse spider will only bite when it meets with pressure from a human. For example, if you place your foot in your shoe, not knowing a spider was inside, you would be bitten. Brown recluse spider bites may sting at first, then feel painful. You may notice a small white blister at the site of the bite.
Symptoms usually last for 24–36 hours and include:
The brown recluse bite can cause the skin to deteriorate, known as skin necrosis, and needs medical treatment right away.
Black widow spiders are black, with a red hourglass pattern on their underside. Black widow spiders are mostly found in the U.S. South and the West but can live anywhere in North America.
They prefer to live in undisturbed areas and may be found under woodpiles. They can also live near outdoor toilets because of the abundance of flies, which they will eat.
Black widow spiders tend to build their webs between objects. These spiders usually bite when a human comes into contact with one of their webs.
A black widow spider bite has two puncture marks. Because this spider's venom is a neurotoxin (poison that impacts the nervous system), the pain will start at the site of the bite and then spread to other areas of the body.
Other symptoms may last for several days and include:
If you begin to experience serious symptoms from a spider bite, see your healthcare provider right away. These symptoms include trouble breathing, increased blood pressure, muscle tension, and weakness.
The venom from a spider bite could put the body into shock. Symptoms of shock include pale skin, sweating, rapid breathing and heartbeat, confusion, cool hands and feet, and loss of consciousness.
Identifying a brown recluse vs. a house spider is a helpful way to know if your bite is poisonous.
0.25–0.75 inches long
Golden-brown color
Violin-shaped marking on the back
Six eyes
Less than 0.25 inches long
Brown color, may have brown or white spotting on the belly
Dark rings on the legs
Eight eyes
Fortunately, most spider bites heal on their own without the need for medical intervention. First, move away from the spider while staying as calm as you can.
To care for a nonvenomous spider bite at home, start by cleaning the area with soap and water. Clean the skin surrounding the bite as well. If the bite is painful or itchy, apply an ice pack or a cold, damp washcloth.
You may need to take over-the-counter pain medication if the bite is sore. Antihistamine medications like Benadryl (diphenhydramine) may decrease itching and swelling.
If your symptoms do not improve or start to worsen with home remedies, contact your healthcare provider. There is a risk of infection with any insect bite. Seek medical care if you notice any of the following symptoms:
If you believe that you have been bitten by a dangerous spider, like a black widow or brown recluse, seek medical attention right away.
To treat a venomous spider bite at home, wash the area well and then apply ice. The ice will help to slow your body’s absorption of the spider’s venom. Elevate the limb or area of the body that was bitten and try to remain still. Then seek medical treatment.
When you seek medical care for a possibly venomous spider bite, your healthcare provider will start by inspecting the bite mark. There is no way to test for a spider bite. Your practitioner may diagnose one based on an examination of the wound.
Once it is determined that your bite requires treatment, the healthcare provider will discuss a plan with you. Treatment for spider bites typically involves addressing the symptoms as they occur. If you have a heart condition, your healthcare provider may recommend admitting you to the hospital for observation and treatment.
Consult your healthcare provider right away if you develop any serious symptoms, such as:
Most spider bites are harmless and do not require treatment. Spiders usually do not bite unless they feel trapped or threatened. Bites from brown recluse spiders and black widow spiders are dangerous because of the spiders’ venom. Seek medical care right away if you believe that you were bitten by a poisonous spider.
Being bitten by a spider can be frightening and painful. Fortunately, most of these bites are not dangerous and do not require treatment. If you are concerned that you have a poisonous spider bite, try to stay as calm as possible. While this is easier said than done, it can help to slow the absorption of venom. Seek medical care for next steps.
Brown recluse spiders live in the Midwestern and Southern states in the United States. They tend to seek out dry, sheltered areas like piles of leaves, rocks, or wood. Indoors, they may live in dark areas like closets, basements, or attics.
The Centers for Disease Control and Prevention (CDC) does not recommend attempting to remove the venom from a spider bite.
Most spider bites cause only mild symptoms and heal within a few days. Black widow bites may cause symptoms for several days.
Yes, it may be possible to identify a venomous spider bite by inspecting the bite. Unlike other types of bites, black widow bites usually have two puncture sites. The bite will often feel like a sharp pain, followed by numbness. A bite from a brown recluse spider usually appears as a blister surrounded by a bruise.
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MedlinePlus. Spider bites.
Johns Hopkins Medicine. Spider Bites.
Centers for Disease Control and Prevention. Venomous spiders.
OSHA Fact Sheet. Brown recluse spider.
Johns Hopkins Medicine. Spider bites.
OSHA Fact Sheet. Black widow spider.
MedlinePlus. Shock.
National Wildlife Federation. Common house spider.
University of Michigan Health. Nonpoisonous spider bites.
Centers for Disease Control and Prevention. Symptoms of venomous spider bites.
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