Mythbusters: Spiders and bites

MYTH: Spiders are everywhere and they bite people all the time.

MYTH STATUS: Partially true.


Are spiders really everywhere?

Spiders get a really bad rap. 

Like really, really bad. And they’ve not done much to earn their negative reputation.

While it’s true that there are a lot of spiders hanging out around us, they are a lot less nefarious than our human lore has made them out to be. We get it, people fear spiders – there’s a reason that the movie Arachnophobia was so popular. But let’s talk facts and fiction, okay?

spider on grass

Yes, spiders are certainly plentiful. After all, there are an estimated 3,500 species in North America alone, most that you’ve probably never heard of. 

You’ve probably even come across the oft-internet repeated fiction that “You’re never more than a few feet away from a spider.” While this could be true, the truth of the matter is that it really depends on where you are. 

Spiders are predatory, which means that they are constantly hunting for food. So, reason dictates that they are going to be hanging out in environments where their food is plentiful. If your environment has lots of insects, then the chance of spiders taking up residence there is going to increase. However, if you’re working somewhere that is, by nature, relatively insect-free – such as in a pharmaceutical lab where cGMP standards are critical to product integrity – the chances of a large spider population being there is going to significantly decrease. 


Do all spiders bite?

So now to the second part of the myth – spider bites

Again, spiders get maligned. They get blamed for a lot of skin irritations that they had nothing to do with. 

While it’s true that all spiders CAN bite and have fangs, the truth is, spiders only bite out of necessity, to paralyze their prey or defend themselves. 

Most spiders’ jaws aren’t strong enough to break through human skin. So, unless you see a spider actually biting you or are able to see two small fang marks, that unidentified mark on your skin could be from just about anything. 

However, part of the problem is that it is very hard to identify a spider bite; even medical professionals can’t diagnose most spider bites with 100 percent certainty. There are a few exceptions — species that are of medical importance and whose bites have distinctive indications.

red bites on skin
Spiders often get blamed for skin irritations or conditions that aren’t actually spider bites.


So, if it’s not a spider bite, what is it? Research done over the past ten years has shown that many skin conditions originally attributed to spiders are really caused by other things. There are a number of other potential causes. 

  • Other insect bites (fleas, bed bugs, etc.)
  • Reactions to common products and chemicals (laundry detergents, soaps, lotions, cleaning products, etc.)
  • Skin infections or irritations attributed to other medical causes, including methicillin-resistant Staphylococcus aureus (MRSA) infections and the herpes zoster virus (shingles). 


But spider bites can happen, right?

Yes. Spider bites can and do happen. Spiders will bite if they feel threatened. And you may have a reaction. Here’s why:

When a spider bites you, proteins from its saliva are injected into your skin. Your body may have a localized reaction to those foreign proteins – redness, minor swelling, mild pain or irritation, usually in the area right around the site of the bite. These types of reactions happen within the first 24 hours and subside relatively quickly; within a few days, typically. This is no different from how many people react to mosquito bites. 

Now, that’s not to minimize skin irritations. Some can be serious. If you have a skin irritation that is hot to the touch, produces moderate to severe swelling, is accompanied by anaphylaxis (difficulty breathing, swelling of tongue or airways, dizziness, loss of consciousness), creates an ulcer or lesion, or is accompanied by a high fever or neurological symptoms (muscle spasms, nausea, vomiting, sweating, tremors, weakness), seek medical attention right away. Spider bite or not, these are signs of a more serious condition.


What types of spiders can have dangerous bites?

There are a few species of spiders in North America that can have bites with serious consequences, rendering them medically important. Two are well-known and their bites have been studied and documented. 

Some doctors and entomologists have also pointed to a third species that may have a bite that packs more punch: the hobo spider, which is endemic to the Pacific Northwest. However, more research needs to be done to determine whether or not this spider’s venom is harmful to humans. Most reports associated with the hobo spider fail to show proof definitively linking the hobo spider to the adverse reaction.

The brown recluse spider can be identified by the distinctive violin shape near its head.

Brown recluse spider bites

It is important to note that with many brown recluse spider bites, reactions are often not severe; however, they can be, and that’s why we must give them attention. If the spider’s bite includes a large enough dose of hemotoxic venom, it can cause necrotic wounds or lesions that can take months to heal or even require surgical repair. Reactions can also vary based on the health and age of the bite victim. Those that are immunocompromised or have conditions such as diabetes may have a more severe reaction.


Though many spiders don’t present an actual threat to humans, no one wants them hanging around their business. From the fear they insight in passersby to their unsightly webs, it’s better to keep them outside. If you’re seeing an increasingly large population of spiders on your property, contact Rentokil today.

Nancy Troyano

Nancy received her PhD in Entomology from Virginia Tech, with research primarily focused on virus transmission by mosquitoes. Nancy is also a Board Certified Entomologist, skilled in medical, veterinary and urban entomology. In 2009, Nancy began working for Rentokil North America, a billion dollar organization, where she currently serves as the Director of Operations Education and Training. Nancy is responsible for leading and supporting education and training for all lines of business and at all levels of the operation, which includes over 4500 pest technicians. She develops comprehensive academic programs and pest management courses that are utilized globally, and oversees a team that manages all of the learning and development needs of the organization. Additionally, Nancy provides ongoing technical support to field operations and acts as a subject matter expert for vector management programs.

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