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updated October 08, 2010

Spider bites

Filed under: Beauty & Plastic Surgery
Spider bites are uncommon. Often, people mistake a skin infection or a bite by another insect as a spider bite.

Only a few spiders have fangs strong enough to pierce your skin and enough venom to cause a reaction. In the U.S., these include the black widow spider and the brown recluse spider. Even these types of spiders tend to bite only when threatened.

Spider bites are rarely lethal. Treating the site of the spider bite is generally all that's necessary. In a few cases, symptoms may be severe and widespread enough to require antivenom treatment and hospitalization.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Typically, a spider bite looks like any other bug bite — a red, inflamed, sometimes itchy or painful bump on your skin — and may even go unnoticed. Harmless spider bites usually don't produce other symptoms.

Symptoms of a black widow spider bite
Symptoms of a black widow spider bite depend on the area of the body bitten, how much venom was introduced and how sensitive you are to the venom. The venom can travel through your bloodstream and affect your nervous system, causing varying degrees of pain. Typical signs and symptoms include:

  • Mild stinging sensation when bitten (or no pain at all)
  • Slight swelling around one or two small bite marks
  • Dull, numbing pain progressing from the bite site to your abdomen and back (usually within an hour of being bitten)
  • Severe cramping or rigidity in your abdominal muscles

Other systemic signs and symptoms — ones that affect the whole body — that sometimes occur include:

  • Generalized, severe pain in your muscles and joints, abdomen or back
  • Nausea and vomiting
  • Dizziness
  • Profuse sweating
  • Tremors
  • Restlessness and anxiety
  • Increased blood pressure
  • Fever
  • Difficulty breathing
  • Facial swelling
  • Rash

Pain usually persists for the first eight to 12 hours. Signs and symptoms diminish and go away after several days, although you may still feel weak and experience residual spasms and restlessness for next few weeks or months.

Symptoms of a brown recluse spider bite
Usual signs and symptoms of a brown recluse spider bite include:

  • Mild burning or stinging sensation when bitten (or no pain at all)
  • Redness and slight swelling around two small bite marks
  • Increasing pain over the next two to eight hours, which may become severe

Over the course of several days, other less common signs and symptoms may appear:

  • Formation of a dusky red or blue (blood-filled) blister at the bite site, which then ruptures and sloughs off to leave a deep, enlarging ulcer (necrosis).
  • General feeling of illness
  • Nausea and vomiting
  • Fever
  • Body aches

When to see a doctor
A bug bite isn't usually a reason to see your doctor, especially since it's often hard to determine if the bite was from a spider and what kind of spider. But if you believe you've been bitten by a black widow or brown recluse spider, or you start to experience severe pain or cramping in your abdomen or back after a spider bite, see your doctor promptly.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Severe spider bite symptoms occur as a result of injected spider venom circulating through your bloodstream. The severity of symptoms depends on the type of spider, the amount of venom injected and how sensitive your body is to the venom.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Although dangerous spider bites are rare, your risk of being bitten increases if you live in the same areas that the spiders do and you happen to disturb their habitat. Both black widow and brown recluse spiders prefer warm climates and dark, dry places.

Location and habitat of black widow spiders
Black widow spiders can be found throughout the U.S. but more so in Maryland and southern Ohio and the southwestern states.

They generally prefer to live outdoors, in places such as:

  • Sheds
  • Garages
  • Unused pots and gardening equipment
  • Woodpiles

Location and habitat of brown recluse spiders
Brown recluse spiders are found most commonly in the southern Midwest and in limited areas of the Southwest.

Recluses are so named because they like to hide away in undisturbed areas. They mostly prefer to live indoors, in places such as:

  • The clutter of basements or attics
  • Behind bookshelves and dressers
  • In rarely used cupboards

Outside, they seek out dark, quiet spots, such as under rocks or in tree stumps.

Spiders in general, including the black widow and brown recluse, bite only as a last defense when being crushed between your skin and another object.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Very rarely, a bite from a black widow or brown recluse spider may lead to serious complications, such as a coma, kidney failure or death.

People who are more susceptible to severe complications include:

  • Infants and young children
  • Adults over 60 years of age
  • People with a heart condition

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

If you've been bitten by a spider that you suspect is a black widow or brown recluse, call your primary care doctor or go to an urgent care center. If your doctor has online services, an option may be to email a picture of the spider to your doctor.

What you can do
To help your doctor understand your symptoms and how they might relate to a spider bite, you can:

  • Bring the spider with you, if you have it and it's still intact. Or bring a photo of the spider, if that's more feasible. Since these spiders can be difficult to identify, your doctor may send it to a person who specializes in studying spiders (arachnologist) or insects (entomologist).
  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Make a list of your activities around the time you started experiencing symptoms, as well as the setting, whether in your own backyard or on a trip away from home.
  • Take a family member or friend along who might help you remember details of the bite.
  • Write down questions to ask your doctor.

Some basic questions you might want to ask include:

  • If this is a dangerous spider bite, what's the next best step?
  • If this isn't a spider bite, what are possible causes for my symptoms or condition?
  • Do I need any tests?
  • How long will my symptoms last?
  • What is the best course of action?
  • I have these other health conditions. How will that affect my condition now?
  • Are there any restrictions that I need to follow?
  • Should I see a specialist? What will that cost, and will my insurance cover seeing a specialist?
  • Is there a generic alternative to the medicine you're prescribing me?

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

  • When did you begin experiencing symptoms?
  • Have your symptoms been continuous or occasional?
  • How severe are your symptoms?
  • What, if anything, seems to improve your symptoms?
  • What, if anything, appears to worsen your symptoms?

What you can do in the meantime
While you're waiting to see your doctor, clean the bite with mild soap and water, apply a cold pack and elevate the affected body part. To relieve pain, take a pain reliever such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, others).

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

Your doctor may suspect a spider bite based on your history and your signs and symptoms, but a specific diagnosis is difficult to confirm. Confirmation requires:

  • An eye witness to the bite
  • Identification of the spider by an expert
  • Exclusion of other possible causes

The black widow spider is a shiny black spider about a half-inch (12 to 13 millimeters or mm) long with a red hourglass (or two triangles) marking on the underside of its abdominal area.

The brown recluse spider is a brown, nondescript spider about a quarter-inch to three-quarters of an inch (6 to 19 mm) long. It has a dark violin shape on top of the leg attachment region but this can be hard to identify. Another characteristic of the brown recluse is that it has six eyes — a pair in front and a pair on both sides — rather than the usual eight eyes in two rows of four.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

If a spider has bitten you, try to identify the spider and, if possible, collect it and place it in a bag for later confirmation. If you think it was a black widow or brown recluse spider, stay calm and call your doctor, a hospital or 800-222-1222 to access your local poison control center.

Primary treatment for all spider bites
For most people with spider bites, including black widow and brown recluse spider bites, the following treatment measures are all that's required:

  • Clean the bite with mild soap and water.
  • Apply cold packs to the bite, to reduce pain and inflammation.
  • If the bite is on an extremity such as an arm or leg, keep it elevated.
  • Take over-the-counter pain relievers as needed.
  • Observe the bite for signs of infection.

Your doctor may also recommend a tetanus booster shot if you haven't had one in the last five years. Antibiotics may be prescribed if a bacterial infection develops in the bite. Both black widow and brown recluse spider bites generally heal without leaving any scar.

Treatment for black widow spider bites
Certain people may require hospitalization after a black widow spider bite, for supportive therapy and monitoring:

  • Children under 16 years of age
  • Adults over 60 years of age
  • People with high blood pressure
  • People with severe symptoms affecting the whole body

If you have severe symptoms, your doctor may recommend an antivenom, which may be injected into a thigh muscle or given through a vein (intravenously). The antivenom works for up to 36 hours after the bite and helps to reduce pain and the need for hospitalization. There is a risk of an allergic reaction to the antivenom, so it should always be given in a setting of continuous monitoring by staff equipped to treat a severe reaction.

Treatment for brown recluse spider bites
Your doctor may recommend a drug called dapsone to prevent or treat ulceration (necrosis) of a brown recluse spider bite. Dapsone is usually given twice a day over the course of 10 days. Before receiving dapsone, you may be screened for deficiency of an enzyme called glucose-6-phosphate dehydrogenase (G6PD). This enzyme deficiency can interact with dapsone to cause other, potentially more serious complications.

In a very few cases, surgical removal of ulcerated tissue may be performed. This is usually done only after the ulceration has stabilized.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

To prevent spider bites:

  • Wear a long-sleeved shirt, hat, gloves and boots when handling stored boxes or firewood, and when cleaning out sheds, garages, basements, attics and crawlspaces.
  • Inspect and shake out gardening gloves, boots and clothing that have been unused for a while.
  • Use insect repellants, such as DEET or Picaridin, on clothing and footwear.
  • Keep insects and spiders out of the house by installing tight-fitting screens on windows and doors, and caulking or sealing cracks or crevices where spiders can come in.
  • Discard old boxes, clothing and other unwanted items from storage areas.
  • Store items you want to keep off of the floor and away from walls.
  • Remove piles of rocks or lumber from the area around your house.
  • Avoid storing firewood against the house.
  • Vacuum spiders and spider webs, and dispose in a sealed bag outside to prevent re-entry into the house.

©1998-2013 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.
Read this article on Mayoclinic.com.

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