SPIDER BITES: Facts versus Myths

Whether it be Blacksburg, Christiansburg, Pulaski, Roanoke or other communities throughout the New River Valley & Southwestern Virginia, Arachnophobia ranks as one of the most common phobias among adults. Even people with less severe spider fears may feel a visceral shudder at the thought of an eight-legged creature lurking in their home, let alone crawling across their skin. But is this fear warranted? How dangerous are spiders?

Spiders usually bite only when they feel threatened. Most of the time this is because they’ve taken up residence under an article of clothing or a blanket, and are about to get squeezed when a person attempts to put on said clothing or snuggle into their blanket. Spiders do not seek out human bodies on purpose for their warmth. They are not blood feeders like mosquitoes, ticks, or bedbugs. They do not lay their eggs on or in people. If anything, most spiders actively try to avoid us. 

Many things are often confused or misdiagnosed as spider bites, including bacterial infections like MRSA and blood-feeding insects like fleas or bedbugs. Other medical conditions that may get misdiagnosed as spider bites include various cancers, diabetic ulcers, Lyme disease, burns, bed sores, and reactions to medications. Spider bites do not cause multiple lesions on the body at the same time. A spider won’t run around someone’s body biting several areas. In addition, spider bites are incredibly rare, so having multiple lesions over a period of time is not likely to be due to a spider. It is more likely a bacterial infection or blood-feeding insect. Likewise, the odds of more than one person in the same household being bitten by a spider are extremely low, so multiple people experiencing lesions also points to some other cause. 

All spiders are venomous. However, not all spider venoms are the same. Venom is one of the key adaptations that have allowed spiders to be successful creatures. It helps them to subdue their prey, mainly insects, and so targets insect biochemistry, not that of us vertebrates. Even if a spider is big enough to bite and pierce human skin (and many are not), the toxins within that venom are for taking down prey much smaller than a person and usually does not affect our systems to the point of being medically significant. A generic spider bite may cause redness, swelling, and itching at the bite site for a few days. 

There are two spiders whose bites can be medically significant - the black widow and the brown recluse. Black widow venom targets the nervous system. It blocks the neurotransmitters that facilitate muscle contraction from being reabsorbed back into the neuron that released them, and so permanently turns on muscle contraction. Symptoms include muscular pain and aches. It can also impact autonomic nervous system functions like sweating. Sometimes there are red streaks running away from the bite toward the center of the body, indicating inflammation of the lymph nodes. Black widow bites are usually treated with pain relievers, benzodiazepines, or antivenin. Black widow spiders are common in the southern and western parts of America. However, they prefer to keep to themselves in dark, hidden areas and are not likely to seek you out.

Brown recluse spider venom is cytotoxic. In 90% of brown recluse bites, symptoms are no more severe than a generic spider bite. However, in some cases a necrotic wound develops and leads to tissue loss. In very rare cases involving small children, there can be a systemic response that involves the circulatory system. This can rupture red blood cells, damage kidneys, and can be fatal. There is no consensus on the best treatment for recluse bites. Many wounds heal spontaneously. RICE (rest, ice, compression, elevations) seems to be sufficient for most recluse bites. Brown recluse spiders are not widespread across America. They are limited to the central midwest - from southeastern Nebraska down to Texas and east to southwestern Ohio and northwestern Georgia. They also seem to be more rare along the gulf coast and more common heading inland.They are not typically found along the east coast or mid-Atlantic region. 

The takeaway: Spiders are not likely to bite you unless as a last resort. And even if they do, most of them have fangs too small to pierce your skin. And even if one did, most of them have venom with little to no effect on people. And your odds of coming across a brown recluse are extremely low unless you live in the central US.