Spider BitesDr. Jorge Parada
- National Pest Management Association
Monday, November 5, 2012
Harry Potter’s friend, Ron Weasley, is probably in good company
when he admits he hates spiders. But how much of spiders’ negative
notoriety is really just a bad rap?
In truth, spiders are not intentionally harmful to
humans. Most spider bites occur when humans accidentally trap or
brush up against a spider and receive a defensive bite. On rare
occasions, spiders may have a serious lapse in judgment and bite a
human finger (or other body part) mistaking it for a caterpillar or
other such prey. Even then, most spiders are too small and not
capable of breaking the skin with their fangs, or their venom too
weak to be dangerous to humans. Simply put — most spider bites are
accidental, harmless and require no specific treatment.
Still, that is not enough to stop spiders from having a bad
reputation. It is common for any unexplained skin irritation to be
called a "spider bite." In fact, most skin lesions and symptoms
that are attributed to spiders are rarely actually due to a spider
bite. Research has shown that 80 percent of presumed spider bites
are actually bites from other insects, or due to skin infections
such as MRSA (a resistant staph infection).
Yet, occasionally, a spider’s bites will cause real harm. Spider
bites may cause injury by three mechanisms. First, especially with
larger spiders, the bite itself may be painful and cause injury.
However, far more concerning is the spider's venom,
which can include necrotic agents or neurotoxins. Spider bites
rarely transmit infectious diseases.
Most spider bites are less painful than a bee sting. Pain from
non-venomous spider bites typically lasts for five to
60 minutes while pain from venomous spider bites frequently
lasts for longer than 24 hours. The rate of a bacterial
infection due to a spider bite is low (less than one
The two spiders of greatest concern in the United States are the
recluse and the black widow
spiders, most commonly found in southern states. Both species
prefer warm climates and dark, dry places. Typically, these are
timid, non-aggressive spiders, often found in dry, littered,
undisturbed areas such as closets, woodpiles and under sinks.
Black widow spiders can be found throughout North America, but
are most common in the southern and western areas of the United
States. Male widows, like most spider species, are much smaller and
generally less dangerous than the females. Widows tend to be
non-aggressive, but will bite if the web is disturbed and the
spider feels threatened. The more dangerous female is a dark
colored spider and with a red hourglass marking on its belly. The
bite feels like a pinprick, and at first may go unnoticed or seem
rather minor. Early on there may be slight swelling and faint red
marks. Within a few hours, though, intense pain and stiffness
begin. Other signs and symptoms include: chills, fever, muscle
cramps, and gastrointestinal symptoms such as nausea, vomiting and
severe abdominal pain. Typically, black widow bites are less
common, but more severe than brown recluse bites. That said, no one
in the United States has died from a black widow spider bite in
more than 10 years.
The brown recluse spider, also known as the violin spider, is
most commonly found in the south-central, mid-western and southern
states of the United States. Most encounters with this spider occur
from moving boxes or rooting about in closets, attics, garages or
under beds where they may have nested. These spiders are brown in
color with a characteristic dark violin-shaped (or fiddle-shaped)
marking on its head. Whereas most spiders have eight eyes, brown
recluses have six equal-sized eyes. The bite produces a mild
stinging, followed by local redness and intense pain within eight
hours. A fluid-filled blister forms at the site and then sloughs
off to leave a deep, enlarging ulcer. Systemic (or generalized)
reactions from a brown recluse spider bite vary from a mild fever
and rash to nausea and listlessness. Generally, brown recluse
spider bites are reported much more frequently than black widow
bites, but while the brown recluse bite may cause very significant
local skin reactions, it is much more unusual for these bites to
cause generalized symptoms. Unfortunately, brown recluses are
almost communal and can be sometimes be found in great numbers.
What To Do
- If you suspect a spider has bitten you, try to bring it with
you to the doctor so they can determine the best course of
treatment based on the species.
- Clean the site of the spider bite well with soap and
- Apply a cool compress over the spider bite location (using a
cloth dampened with cold water or filled with ice).
- If you suspect the bite is form a black widow or brown recluse
spider, and the bite is on an extremity, elevate it.
- Consider tying a snug bandage above the bite and elevate the
limb to help slow or halt the venom's spread. Ensure that the
bandage is not so tight that it cuts off circulation in your arm or
- Adults can take aspirin or acetaminophen and antihistamines to
relieve minor signs and symptoms (but use caution when giving
aspirin to children or teenagers).
- Seek medical attention for any severe signs and symptoms, or if
signs and symptoms continue to worsen for more than 24 hours.
If a local reaction continues to get worse for more than 24
hours, it may be time to seek medical attention. Look for redness
spreading away from the bite, drainage from the bite, increase in
pain, numbness/tingling, or a discoloration around the bite that
looks like a halo or bull’s-eye. If generalized symptoms set in, be
concerned. In very rare cases, there have been reports of spider
bites (by spiders considered otherwise harmless) causing allergic reactions - including anaphylactic shock, a life-threatening
condition (much like may result from the sting of a bee, or wasp in a
highly allergic person).
Contact a pest
professional if you think you may be dealing with a spider
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