Warts are caused by the human papillomavirus, or HPV. There are over 100 types of HPV, and different strains tend to target different parts of the body, which is why warts can show up on your hands, feet, face, or genitals. The virus triggers excess cell growth in the outer layer of skin, producing the rough, raised bumps most people recognize as warts.
How HPV Gets Into Your Skin
HPV infects the basal keratinocytes, the deepest cells in the outer layer of your skin. The virus doesn’t need a large wound to get in. A tiny cut, a hangnail, a patch of dry cracked skin on your heel, or even a micro-abrasion you can’t see is enough. Once inside, the virus hijacks normal skin cells and forces them to reproduce faster than usual, building up the thick, textured growth you see on the surface.
Researchers have found that the initial steps of infection actually happen at the basement membrane, the thin barrier between the outer skin and the tissue underneath, before the virus even binds to a cell’s surface. In some cases, HPV can settle into hair follicle stem cells, creating a reservoir where the virus persists quietly for long periods. This helps explain why warts sometimes reappear in the same area after you thought they were gone.
How Warts Spread From Person to Person
Warts are contagious. They spread through both direct and indirect contact. Direct contact means touching someone else’s wart or having skin-to-skin contact with an infected area. Indirect contact means using objects that have touched a wart, like towels, razors, or nail clippers. You can also spread warts to other parts of your own body by touching a wart and then touching another area, especially if the skin there is broken.
Genital warts spread specifically through sexual skin-to-skin contact and are classified as a sexually transmitted infection. The strains responsible for genital warts are different from the ones that cause common hand or foot warts.
Where You’re Most Likely to Pick Up HPV
Warm, moist environments are ideal for HPV transmission. Public showers, pool decks, gym locker rooms, and shared bathing areas all create conditions where the virus thrives on damp surfaces. Walking barefoot in these settings is one of the most common ways people pick up plantar warts on the soles of their feet. The moisture softens skin, making it easier for the virus to enter through small cracks.
Shared personal items also carry risk. Borrowing someone’s towel, using a communal pumice stone, or sharing a razor can all transfer the virus. Even gym equipment handles, while less commonly cited, can theoretically harbor HPV on their surfaces.
Who Gets Warts More Easily
Anyone can get warts, but certain groups are more vulnerable. Children and young adults develop warts more frequently, likely because their immune systems haven’t yet built up defenses against the many strains of HPV circulating in schools, playgrounds, and pools. People who bite their nails or pick at hangnails also face higher risk, because those habits create small openings in the skin around the fingers where HPV enters easily.
A weakened immune system significantly raises your chances. People living with HIV/AIDS, organ transplant recipients taking immunosuppressive medications, and anyone on long-term therapies that suppress immune function tend to develop more warts, larger warts, and warts that are harder to treat. A healthy immune system is your primary defense against HPV, and when it’s compromised, the virus has a much easier time establishing itself and persisting.
How Long Before a Wart Appears
One of the reasons warts are so hard to trace is the long gap between exposure and symptoms. After HPV enters the skin, it can take anywhere from one to 20 months for a visible wart to develop. The typical incubation period is two to three months. This means you may have picked up the virus weeks or months before you notice anything, making it nearly impossible to pinpoint exactly where or when you were exposed.
During this incubation window, the virus is replicating inside skin cells without producing any visible changes. You can potentially spread it to others or to other parts of your body during this time, even though you have no idea you’re carrying it.
Different Warts Come From Different Strains
Not all warts look the same, and that’s because different HPV strains behave differently in different areas of the body:
- Common warts are the rough, dome-shaped bumps that typically appear on fingers, hands, and around the nails. They’re usually skin-colored or grayish.
- Plantar warts grow on the soles of your feet and tend to be flat or grow inward because of the pressure from walking. They often have small black dots, which are tiny clotted blood vessels.
- Flat warts are smaller and smoother than other types. They appear in clusters, sometimes dozens at a time, and are common on the face, arms, and legs.
- Filiform warts are long, narrow growths that tend to appear around the eyes, nose, and mouth.
- Genital warts affect the genital and anal areas and are caused by sexually transmitted HPV strains distinct from those behind skin warts.
Why Your Body Sometimes Clears Warts on Its Own
Your immune system is capable of recognizing and fighting HPV. About 90% of HPV infections are cleared by the body within one to two years. For people with a lower-risk strain and a healthy immune system, the typical clearance window is 12 to 24 months. This is why many warts, especially in children, disappear without any treatment at all.
The catch is that HPV has evolved strategies to evade immune detection. Certain viral proteins alter the body’s immune signaling pathways, helping the virus establish persistent infections in some people. When the immune system does eventually recognize and respond to the infection, the wart shrinks and resolves. But if immunity is weakened or the virus is particularly good at hiding, warts can linger for years or keep coming back after removal.
Treating a wart removes the visible growth, but it doesn’t always eliminate every trace of HPV in surrounding skin cells. This is why recurrence is common and why some people deal with warts repeatedly over the course of several years before their immune system fully suppresses the virus.