What does a spider bite look like?

A spider bite typically looks red and inflamed and sometimes forms a painful bump or is itchy. The vast majority of spider bites are harmless.

What can be mistaken for a spider bite?

Conditions that are frequently mistaken for a spider bite: Allergic contact dermatitis Herpes simplex Impetigo Irritant contact dermatitis Furuncle or boil Lyme disease Other insect bites Poison ivy, oak, or sumac Shingles Staphylococcal skin infection (including MRSA) Syphilis

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.

Infected Sores That Are Not From Spider Bites

It's hard to know the difference between a skin ulcer and a spider bite. Spider bites can get inflamed or infected, and they may require treatment.

If you think that you might have been bitten by a spider, make sure you tell your healthcare providers where you were, what the spider looked like, how long ago it happened, and where on your skin you think the spider might have bitten you.

There are also many different types of skin lesions that can look similar to spider bites but are treated differently than spider bites. If you develop a skin lesion that is painful, tender, swollen, or oozing pus, be sure to get medical attention. This article describes common types of skin lesions that can be mistaken for spider bites.

Allergic Reaction or Shingles?

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

The raised rash in the photo looks like it could be hives or shingles. Shingles rash forms in a line on one side of the body.

It can also be an allergic reaction to any exposure—including a spider bite.

Shingles

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

If you have shingles or are caring for someone with shingles, there are ways to get pain relief. There's also an effective shingles vaccine that can help prevent you from developing this painful condition.

Allergic Reactions

Allergic reactions to bug and spider bites can be deadly if they develop into anaphylactic shock, which causes systemic symptoms—shortness of breath and blood pressure changes. 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.

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.

Diabetes can predispose to cellulitis (inflamed skin cells) that can cause the type of tissue damage seen in this picture. It can also get bad enough to require an amputation.

Staphylococcus aureas and group A streptococcus both cause skin infections that can be mistaken for spider bites.

Whether caused by spider bites or skin infections, wounds like these are painful and dangerous. If you have diabetes, it's important to seek medical attention whenever a wound starts to form—even if it doesn't hurt. Your healthcare provider may be able to identify the cause and treat it before it gets worse.

Why Is it Getting Bigger?

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

Spider bites and other types of infections can show expanding lesions like this one. If a lesion keeps growing, starts oozing, smells bad, gets hot, turns black, starts bleeding, is associated with a fever, or starts showing other signs of an infection, it's time to go to a doctor.

Maybe a Spider Broke the Skin

An infected lesion — This lesion is definitely infected. Kenneth Walker

A spider bite can cause a break in the skin. This can lead to MRSA, a common diagnosis for skin lesions like the one shown in the photo. Having a weak immune system can also make a person susceptible to this aggressive infection.

Toe Blister Is Not a Spider Bite

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

This is a skin infection from MRSA. The blister will probably break and drain at some point, but you don't want to encourage it prematurely. Popping the blister can introduce another form of bacteria and possibly make the infection worse.

Frequently Asked Questions

What does a spider bite look like?

A spider bite typically looks red and inflamed and sometimes forms a painful bump or is itchy. The vast majority of spider bites are harmless.
What can be mistaken for a spider bite?
Conditions that are frequently mistaken for a spider bite:
- Allergic contact dermatitis
- Herpes simplex
- Impetigo
- Irritant contact dermatitis
- Furuncle or boil
- Lyme disease
- Other insect bites
- Poison ivy, oak, or sumac
- Shingles
- Staphylococcal skin infection (including MRSA)
- Syphilis
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.

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.

Gaver-Wainwright MM, Zack RS, Foradori MJ, Lavine LC. Misdiagnosis of spider bites: bacterial associates, mechanical pathogen transfer, and hemolytic potential of venom from the hobo spider, Tegenaria agrestis (Araneae: Agelenidae). J Med Entomol. 2011;48(2):382-8. doi:10.1603/ME09224
MedlinePlus. Shingles.
Cronan KM. First aid: Spider bites. KidsHealth from Nemours.
Jenkins TC, Knepper BC, Jason Moore S, Saveli CC, Pawlowski SW, Perlman DM, McCollister BD, Burman WJ, Diabetes mellitus and skin infections. J. Hosp. Med 2014;12;788-794. doi:10.1002/jhm.2267
Chauhan H, Patil S, Hajare A, Krishnaprasad K, Bhargava A. Necrotizing fasciitis of hand by nethicillin resistant Staphylococcus aureus (MRSA) - a sinister. J Clin Diagn Res. 2015;9(6):DD01–DD2. doi:10.7860/JCDR/2015/12381.6014
Powers J, McDowell RH. Insect bites. In: StatPearls [Internet].
Rahmani F, Banan Khojasteh SM, et al. Poisonous spiders: bites, symptoms, and treatment; an educational review. Emerg (Tehran). 2014;2(2):54-8.

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.

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Infected Skin Lesions That Are Not From Spider Bites