You have warts because your skin has been infected by human papillomavirus, or HPV. This is one of the most common viral infections in humans, and it causes skin cells to grow abnormally fast, forming the rough, raised bumps you see on your skin. The tricky part is that you may have picked up the virus weeks or even months before the wart appeared, so pinpointing exactly when or where you were exposed can be difficult.
How HPV Gets Into Your Skin
HPV doesn’t infect healthy, intact skin easily. It needs a way in. The virus enters through tiny breaks in the outer layer of your skin, and those breaks don’t have to be visible. A paper cut, a hangnail, a scrape, or even the microscopic tears caused by shaving are all large enough for the virus to slip through.
Once inside, the virus targets the dividing cells at the base of your skin. It hijacks the cell’s normal growth cycle, causing those cells to multiply faster than they should. The result is a dense, rough lump of extra skin tissue: a wart. The virus is clever about timing, too. It syncs its activity to your skin cells’ natural cycle of division and maturation, which is why warts can persist for so long.
Where You Likely Picked It Up
HPV spreads two ways: direct skin-to-skin contact with someone who has the virus, or indirect contact with a contaminated surface. You’re at higher risk of picking it up if you:
- Walk barefoot in pool areas, communal showers, gyms, or locker rooms
- Share unwashed towels, socks, or razors
- Have skin that’s been softened by water (which makes it more vulnerable to micro-damage)
- Handle raw meat, poultry, or fish regularly
- Bite or pick at your nails
The virus can survive on surfaces for a period of time outside the body, which is why warm, damp environments like pool decks and shower floors are common sources. Someone with a plantar wart walks barefoot on a wet floor, sheds virus particles, and the next barefoot person with a tiny crack in their heel picks it up.
Why It Took So Long to Show Up
One reason warts seem to appear out of nowhere is the long gap between infection and the visible bump. For genital warts, the incubation period averages two to three months but can range from one to 20 months. Skin warts on the hands and feet follow a similar pattern. You could have been exposed at a pool last summer and only now be seeing the result.
How You Might Be Spreading Them to Yourself
If you started with one wart and now have several, you’re likely spreading the virus from one part of your body to another. Dermatologists call this autoinoculation, and certain habits make it much more common.
Shaving is one of the biggest culprits. If you shave over a flat wart on your leg, the blade picks up virus particles and drags them across fresh micro-cuts in the surrounding skin. This can scatter flat warts across the entire area you shaved. Scratching a wart and then scratching elsewhere on your body does the same thing. Nail biting is particularly problematic: biting a wart on your finger can transfer the virus to your lips, leaving you with warts in both places.
If you have an active wart, avoid picking at it, and don’t shave directly over it. Use a separate razor for areas near warts, or skip shaving that spot until the wart is gone.
Why Some People Get Warts and Others Don’t
Almost everyone is exposed to HPV at some point, but not everyone develops visible warts. The difference comes down to your immune system. Children and teenagers are especially prone to warts because their immune systems haven’t built up defenses against as many HPV strains yet. People with weakened immune systems, whether from organ transplants, certain cancers, HIV, or immunosuppressive medications, often develop widespread or stubborn warts because their bodies can’t fight off the virus effectively.
Pregnancy also increases susceptibility, as does having eczema alongside asthma or hay fever. Even without any of these factors, some people simply have immune systems that are less effective at recognizing and clearing HPV. There’s a genetic component to this that researchers are still working to fully understand.
Different Types of Warts
Not all warts look the same because different strains of HPV target different areas and produce different growths. There are over 100 known strains of HPV, but only a handful cause the warts you see on your skin.
Common warts are the rough, dome-shaped bumps most people picture. They typically appear on fingers, hands, and knees. Plantar warts grow on the soles of your feet and can feel like you’re walking on a pebble because the pressure pushes them inward rather than outward. Flat warts are smaller and smoother, often appearing in clusters on the face, arms, or legs. They’re the type most commonly spread by shaving. Filiform warts are long and narrow, often popping up around the mouth, nose, or eyes.
Do Warts Go Away on Their Own?
Many warts do resolve without treatment, but the timeline depends on your age and the location. Children can generally expect warts to clear on their own within one to two years as their immune system learns to fight the virus. Adults are less lucky. Warts in adults tend to be more persistent, and plantar warts on the feet are especially stubborn regardless of age.
Whether to treat a wart or wait it out depends on how much it bothers you. Warts that are painful (especially plantar warts), spreading, or in a visible spot like the face are reasonable candidates for treatment. Over-the-counter options containing salicylic acid work by dissolving the extra skin layer by layer. A dermatologist can freeze warts with liquid nitrogen, which triggers a blister that lifts the wart off as it heals. Both approaches often require multiple sessions over several weeks.
Even after successful treatment, warts can come back. The virus may still be present in the surrounding skin at levels too low to see, and it can reactivate if your immune system dips.
Growths That Look Like Warts but Aren’t
Not every rough bump on your skin is a wart. Seborrheic keratoses are waxy, scaly growths that commonly appear after age 40 and can look remarkably similar to warts. They’re completely harmless and not caused by a virus. Corns and calluses on the feet can mimic plantar warts, but they’re caused by friction and pressure rather than HPV. One way to tell the difference: plantar warts interrupt the natural lines of your skin (like fingerprints on your foot), while calluses don’t.
Molluscum contagiosum is another viral skin infection that produces small, dome-shaped bumps, but these typically have a tiny dimple in the center and are caused by a completely different virus. If you’re unsure what you’re dealing with, a dermatologist can usually tell the difference with a quick visual exam.