You touched a doorknob at the gym, and two weeks later a rough little bump showed up on your finger. Or maybe you’ve had the same patch on your heel for months and can’t figure out why it won’t budge. Either way, the question is the same: what’s actually causing this? what causes warts?
Warts are caused by the human papillomavirus (HPV), a common virus that infects the outer layer of skin through tiny breaks or cracks. Over 100 HPV strains exist, and different strains target different body parts — which is why a wart on your hand looks nothing like one on your foot or genitals. Most warts are harmless and eventually clear on their own.
What Actually Causes a Wart
Every wart, regardless of where it shows up, traces back to the same root cause: HPV. Once the virus reaches the living cells of your skin — called keratinocytes — it triggers those cells to multiply faster than normal. That overgrowth is the wart itself: a small, rough, raised patch of extra skin cells with the virus living inside them.
This is the detail that trips people up. A wart isn’t a growth “on” your skin — it’s your own skin cells, reprogrammed by a virus, growing in the wrong place at the wrong rate. That’s also why warts can feel stubborn: as long as infected cells are present, the wart can keep rebuilding itself even after you scrape or trim the visible surface.
Quick takeaway: No HPV, no wart. Everything else — how you caught it, why it showed up where it did, why it won’t leave — comes back to this one virus.
How HPV Gets Into Your Skin
Healthy, intact skin is a solid barrier. HPV can’t punch through it on its own. It needs a way in, and that usually means:
- A small cut, scrape, or hangnail
- Skin softened and weakened by moisture (sweaty feet, chewed cuticles)
- A break from shaving, especially on legs or the face
- Dry, cracked skin in winter
Once the virus slips past that barrier, it settles into the basal layer of the skin and starts its slow work. This is also why warts have a delayed appearance — after exposure, it typically takes weeks to several months before a visible bump forms, which makes it almost impossible to pinpoint the exact moment of infection.
How Warts Spread From Person to Person
HPV doesn’t need a dramatic exposure to spread. It moves in three main ways.
Direct contact
Skin-to-skin touch with a wart, or with skin that’s shedding infected cells, is the most straightforward route. This includes something as simple as holding hands with someone who has a wart on their finger.
Indirect contact (fomites)
The virus can survive for a while on damp surfaces — locker room floors, shared shower stalls, communal towels, and even the inside of shoes previously worn by someone with a plantar wart. This is a big reason plantar warts are so common among people who use public pools and gym showers barefoot.
Autoinoculation
You can spread a wart to yourself. Picking at a wart on one finger and then touching another part of your skin — or biting a hangnail near an existing wart — can carry the virus to a new spot. This is why a single wart often turns into a small cluster over time if it’s left alone.
Quick takeaway: Warts spread through contact, not through the air, and you’re just as capable of spreading a wart to yourself as catching one from someone else.
The Different Types of Warts and What Causes Each
Not every wart is the same virus doing the same thing. Different HPV strains prefer different environments on the body, which is why the type of wart tells you something about where and how it likely developed.
| Wart Type | Typical Location | Common HPV Types | Notes |
|---|---|---|---|
| Common warts | Hands, fingers, knees | HPV 2 and 4 (most often), also 1, 3, 27, 29, 57 | Rough, raised, may have tiny black dots (clotted blood vessels) |
| Plantar warts | Soles of the feet | HPV 1, 2, 4, 27, 57 | Flattened by pressure of walking; can be painful |
| Mosaic warts | Balls of feet, under toes | HPV 2 | Cluster of small warts grouped tightly together |
| Flat warts | Face, legs, arms | HPV 3, 10, 28 | Smaller, smoother, often appear in large numbers, more common in children |
| Genital warts | Genital and anal area | HPV 6 and 11 (about 90% of cases) | Sexually transmitted; separate risk profile from skin warts |
| Filiform warts | Around the mouth, eyes, nose | Various HPV types | Thin, finger-like projections |
| Periungual/subungual warts | Around or under nails | Various HPV types | Linked to nail-biting and cuticle picking |
Genital warts deserve a specific note: they’re caused by different HPV strains than the ones behind hand or foot warts, and they spread through sexual skin-to-skin contact rather than casual touch. They’re grouped under the umbrella of “what causes warts” because the underlying virus family is the same, but the transmission and risk context are distinct enough that they’re usually managed separately from common skin warts.
Why Some People Get Warts and Others Don’t
Two people can be exposed to the exact same HPV strain and have completely different outcomes — one develops a wart, the other’s immune system clears it before it ever shows up. Several factors tip the odds:
- Age: Children and teenagers get warts more often, likely because their immune systems haven’t built up prior exposure to common HPV strains.
- Immune status: People who are immunocompromised — due to certain medications, HIV, or organ transplants — develop warts more easily and have a harder time clearing them.
- Skin condition: Frequently wet, cracked, or broken skin (common in swimmers, manual laborers, and people who work with raw meat, sometimes called “butcher’s warts”) gives the virus more entry points.
- Habits: Nail-biting, cuticle-picking, and picking at existing warts all increase exposure and spread.
- Footwear habits: Walking barefoot in communal wet areas raises plantar wart risk significantly.
Quick takeaway: Getting a wart isn’t about hygiene or bad luck alone — it’s a mix of exposure, broken skin, and how your immune system responds to the virus.
Do Warts Go Away on Their Own?
Often, yes. As the immune system eventually recognizes and clears the HPV-infected cells, roughly two-thirds of warts resolve on their own within a couple of years, even without treatment. That’s cold comfort if you have one now, but it explains why doctors frequently recommend watchful waiting for warts that aren’t painful or growing.
That said, “usually harmless” isn’t “always harmless.” In rare cases, a wart-like growth that doesn’t respond to treatment or changes shape can be a sign of verrucous carcinoma, a slow-growing, locally invasive skin cancer that can be mistaken for a stubborn wart. This is uncommon, but it’s the reason a wart that keeps growing, bleeds, or looks different from a typical wart should be checked by a doctor rather than left alone.
Common Wart Myths, Debunked
“Warts come from touching toads or frogs.” No — this is folklore. Warts are caused exclusively by HPV, a human virus. Toads have their own bumpy skin glands, but they don’t transmit warts to people.
“Warts mean you’re not clean.” Also false. HPV spreads through contact regardless of hygiene habits — even meticulously clean people get warts, and plenty of people with less-than-perfect hygiene never do, because it comes down to exposure and immune response, not cleanliness.
“If you cut a wart out, it’s gone for good.” Not necessarily. Because the virus lives in the surrounding skin cells too, warts can return near the original site even after removal unless the infected tissue is fully addressed.
How to Lower Your Risk of Warts
You can’t make yourself immune to HPV entirely, but you can reduce your exposure and the odds of an infection taking hold:
- Wear sandals or shower shoes in locker rooms, public showers, and pool areas.
- Keep cuts, hangnails, and cracked skin covered until healed.
- Avoid picking at your own warts, and don’t share towels, razors, nail clippers, or socks with someone who has one.
- Keep feet dry, since damp skin is easier for the virus to penetrate.
- Talk to your doctor about the HPV vaccine, which protects against several high-risk and wart-causing HPV strains and is most effective when given before exposure.
- If you already have a wart, resist scratching or shaving over it, which can spread it to nearby skin.
The Bottom Line
Warts come down to one cause — HPV getting through a break in your skin — but the story around that cause is more nuanced than most people realize. The strain of virus determines where the wart shows up, your immune system determines whether it takes hold at all, and your habits determine whether it spreads. For most people, patience and basic prevention are enough. If a wart is painful, spreading quickly, or not going away after a couple of years, it’s worth having a doctor take a look rather than waiting it out indefinitely.
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FAQ Section
What virus causes warts?
The human papillomavirus (HPV) causes all warts. There are over 100 identified strains, and different strains tend to cause different types of warts depending on where on the body they infect.
Are warts contagious?
Yes. Warts spread through direct skin-to-skin contact and indirectly through contaminated surfaces like locker room floors or shared towels. You can also spread a wart to a new spot on your own body.
Why do I keep getting warts?
Recurring warts usually mean the virus is still present in nearby skin, or you’re repeatedly exposing yourself to it through habits like nail-biting or walking barefoot in damp public areas. A weaker immune response can also make clearance slower.
Do warts come from toads?
No, this is a myth. Warts are caused only by HPV, a virus that infects human skin. Toads and frogs cannot give people warts.
Can warts spread to other parts of the body?
Yes, this is called autoinoculation. Picking at a wart and then touching another area of skin, especially if it’s cut or damp, can transfer the virus to a new location.
Why do some people never get warts?
Immune response varies from person to person. Some immune systems clear HPV before it ever forms a visible wart, which is why exposure doesn’t guarantee infection.
Do warts go away on their own?
Often, yes. About two-thirds of warts clear up within a couple of years without treatment as the immune system eliminates the infected cells, though this can take time.
What causes genital warts specifically?
Genital warts are caused by HPV types 6 and 11 in roughly 90% of cases. They spread through sexual skin-to-skin contact and are managed differently from common skin warts.
