Infected Sores That Are Not From Spider Bites

Hospital emergency departments get a lot of infected sores that are blamed on spider bites. In reality, most of the "bites" are probably just nasty bacterial infections.

In most cases, the spider is nowhere to be found. Not having the spider makes it hard to positively identify a spider bite.

In the United States, the brown recluse spider is most often blamed for bites, but it only lives in a few Southeastern states. Related spiders live in other areas, but they're not nearly as dangerous as their Dixieland cousins.

Hobo spiders and black widows get blamed nearly as often as the brown recluse.

Healthcare providers are almost as guilty as patients when it comes to incorrectly diagnosing ugly skin ulcers as spider bites. These pictures all show sores that the person—and in some cases, the healthcare provider—thought were spider bites.

Hives or Shingles?

This photo contains content that some people may find graphic or disturbing.

Rash consistent with shingles
Even though he thought it was a spider bite, Jose's rash looks like classic shingles. Jose Luis Balarezo Gardiol

After Jose felt what he thought was a spider bite him in Peru, he developed a rash with muscle pain that seemed to be relieved by an antihistamine (a Peruvian equivalent of Claritin).

The raised rash does resemble hives in the pictures provided by Jose, but the rash also resembles another common condition: shingles.

Jose was not able to see a healthcare provider to treat this rash, so there's no way to know for certain what he had. However, he describes it as traveling from the site of the original bite on his back all the way around to his chest.

That one-sided line is typical in shingles, but could also be an allergic reaction.


Shingles—also known as herpes zoster—comes from the Varicella-zoster virus, the same virus that causes chickenpox. If you experiencing symptoms of shingles, it is important to get an accurate diagnosis and treatment.

If you have shingles or are caring for someone with shingles, there are ways to find comfort. There's also an effective shingles vaccine.

Allergic Reactions

Allergic reactions to bug and spider bites can be deadly if they develop into anaphylactic shock. Usually, if anaphylaxis is going to develop it happens fairly quickly after the bite.

Bee stings are commonly considered the most likely to lead to anaphylaxis.

Bites on Both Feet? Probably Not.

This photo contains content that some people may find graphic or disturbing.

Tissue damage on feet of a person with diabetes
The family of this woman with diabetes believes the original tissue damage started with spider bites. Ivonne H.

Ivonne H. shared this picture of her mother's tissue damage following what the family believes were brown recluse spider bites. According to Ivonne, her mother was bitten twice; on one foot while in Alaska and on the other while in Utah.

With the first bite, Ivonne says her mom felt a sharp pain and ignored it, thinking it was a lost needle in the carpet. She began feeling pain in her leg and went to a healthcare provider who diagnosed it as "​weather-related."

After a while, the pain got worse and the damage became visible. Ivonne say the wound looked like a "colander." Eventually, part of her mother's right foot had to be amputated.

But Were They Spider Bites?

Reading Ivonne's account of her mother's struggle, it's not clear whether a spider had anything to do with the wound.

Ivonne says her mom had diabetes, which often leads to circulation problems that are especially bad in the feet and legs. Many people with diabetes suffer from cellulitis (inflamed skin cells) that can get bad enough to need amputation.

Another cause for skepticism is the claim of two separate spider bites, one on each foot. Spider bites are rare; brown recluse bites are even rarer yet.

The odds of getting a brown recluse bite on one foot in Alaska followed by a brown recluse bite on the other foot in Utah—when neither state is in the brown recluse's known habitat—are extremely small.

Staphylococcus aureas and group A streptococcus both cause skin infections that are regularly mistaken for spider bites. Combined with the increased risk of foot infections in diabetes, it's a perfect storm for bilateral (both right and left) tissue damage of the type in the picture.

Whether caused by spider bites or skin infections, wounds like these are painful and dangerous. It's important to seek medical attention when a wound starts to form. Your healthcare provider may be able to identify the cause and treat it.

Did the Mailbox Bite Her?

This photo contains content that some people may find graphic or disturbing.

Discolored blister
An expanding lesion with a blister in the middle. Nicole Horstmann

A reader sends in this picture from what she believes is a bug bite on her mother. The reader says Mom got ambushed by something at the mailbox on a Thursday and this was how the lesion looked on the following Saturday.

Lots of confirmed spider bites show expanding lesions like this one, but infections can do that, too. As we've seen before, the blister can come from a bite, an infection, or something else entirely.

Very few welts or lesions that can be positively identified as caused by a particular bug or spider. People often want to know what kind of bug did the damage, but the answer has to be: what kind of bug did you see biting you?

If the critter wasn't caught in the act, there's little chance of solving the case.

If a lesion keeps growing, starts oozing, smells bad, gets hot, turns black, starts bleeding, or the victim gets a fever or starts showing other signs of an infection, it's time to go to at healthcare provider.

Maybe a Spider Broke the Skin

This photo contains content that some people may find graphic or disturbing.

An infected lesion
This lesion is definitely infected. Kenneth Walker

This wound was attributed to a spider bite but there was no spider to identify. However, the wound is definitely infected. The patient sought help after two days because the wound was draining pus.

Getting help was the right thing to do. Evidence abounds that what many patients call "spider bites" are really methicillin-resistant Staphylococcus aureus (MRSA) infections.

MRSA can lead to dead tissue (necrotizing fasciitis) like that pictured here. MRSA is also fast becoming the most common diagnosis for skin lesions like these treated in the emergency department.

Toe Blister Is Not a Spider Bite

This photo contains content that some people may find graphic or disturbing.

Blister at the base of the toe
This blister was blamed on a spider, but it turned out to be an infection. Bridget Wuerdeman

Bridget writes that this extremely painful blister led to antibiotic therapy. She doesn't provide a spider to look at, though, which once again raises the point: unless the spider is caught in the act, odds are we're looking at chickenpox, staph or strep infection.

Bridget says she popped the blister after three days because she couldn't take the pain and pressure. She was advised not to by her healthcare provider but did anyway.

There's not really a right or wrong here. The blister would probably break and drain at some point, but you don't want to encourage it prematurely. She could have introduced another form of bacteria and possibly made the infection worse.

It turns out this is not a spider bite at all. It's a skin infection from MRSA. Hopefully, Bridget followed the rest of the healthcare provider's orders, especially about taking all her antibiotics. 

She was right in seeking help for this blister and hoped that sharing it would help others recognize when a blister is more than ill-fitting shoes. Thanks to her for sharing.

Frequently Asked Questions

  • What does a spider bite look like?

    A spider bite typically looks like any other insect bite, with red, inflamed skin and sometimes an itchy or painful bump. The vast majority of spider bites are harmless.

  • What can be mistaken for a spider bite?

    People will often have no recollection of being bitten by a spider, and, in most cases, the "bite" will turn out to be something else. Among the conditions frequently mistaken for a spider bite are:

  • When do you need a healthcare provider for a spider bite?

    Of the 30,000 species of spiders, there are only two in North America that are dangerous: the black widow spider and the brown recluse spider. Both can cause systemic illness, including pain, fever, chills, body aches, cramping, and nausea. Seek emergency care if:

    • You know or suspect you have been bitten by a dangerous spider.
    • You develop painful cramps, profuse sweating, or nausea or vomiting soon after a bite.
    • You experience increasing pain, body aches, fever, or chills within hours of a bite.
    • You have trouble breathing or swallowing.
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7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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