What are plantar warts?
Plantar warts are caused by human papillomavirus (HPV) infecting cells in the thick skin on the soles of the feet. Unlike surface warts, plantar warts grow inward under pressure and become embedded within callus.
What is a mosaic plantar wart?
A mosaic wart is a cluster of multiple wart colonies growing close together beneath a shared callus roof. Each colony contains a mix of HPV-infected cells and normal skin cells, all protected by thick keratin. This structure makes mosaic warts harder to eradicate than single, isolated warts.
How can part of the skin be infected while nearby skin looks normal?
Warts are not solid blocks of virus. Some cells are infected with HPV, while many neighboring cells are not. However, HPV changes how infected cells signal to surrounding cells.
Those neighboring, uninfected cells are induced to overproduce keratin — the thick, rubbery callus that forms the wart’s protective roof. This keratin acts like armor, shielding the infected cells underneath from pressure, immune attack, and treatments.
In mosaic warts, this happens in many nearby islands at once. That is why some parts of a wart can be destroyed while other viral colonies survive under the same callus.
What are the black dots?
Black dots are thrombosed (clotted) capillaries — the tiny blood vessels that supply wart tissue. They are not dirt or seeds.
Their meaning depends on context:
- In an active wart: black dots indicate a living blood supply feeding viral tissue.
- In a dying wart: black dots are damaged or collapsing vessels.
- During healing: dark specks are often residual dried blood and fossilized capillaries being expelled.
This is why black dots can persist or reappear even when the wart itself has been eliminated.
Why do warts look worse after soaking?
Soaking softens and swells keratin. When callus becomes translucent, the hidden internal structure of a wart — lobules, pits, and capillaries — becomes visible.
This makes the lesion look larger, whiter, or more alarming, even though nothing has worsened. Dry skin contracts and hides this architecture, which is why warts often look “better” when dry.
Why did my wart seem to improve, then get worse, then improve again?
This cycle is typical of mosaic warts:
- Dry → looks smoother
- Soaked or debrided → looks worse
- Treated → looks inflamed
- Healing → reveals dead wart scaffolding
Only the return of normal skin lines crossing the area indicates true resolution.
Is redness always bleeding or infection?
No. High-strength salicylic acid pads often contain red-orange dye. As keratin dissolves, the dye stains pores and dead tissue, creating dramatic color that is not blood.
True wart bleeding appears as pinpoint dots or clustered vessels. Dye stains whole surfaces and cracks.
Why do pits, rings, or “holes” remain after the wart is gone?
Mosaic warts create a honeycomb of chambers under the skin. When the viral tissue dies, that scaffolding remains temporarily.
As the sole heals, these empty chambers collapse and fill in. What looks like “new warts” is often just the footprint of old ones.
How do I know when a wart is really gone?
The strongest sign is the return of normal fingerprint-like skin lines crossing the treated area. Active warts disrupt skin lines. Healed skin restores them. Plantar skin regenerates slowly, so this can take weeks even after the infected cells have been eradicated.
Why are plantar warts harder to treat on weight-bearing parts of the foot?
The heel and ball of the foot experience constant pressure from walking and standing. That pressure causes the skin to thicken in self-defense, producing dense keratin.
Unfortunately, this thickened keratin acts as a shield that protects the wart tissue. It blocks freezing, acids, and immune cells from reaching the infected cells. Even when treatment attacks the infected cells, pressure stimulates the skin to rebuild the callus quickly, quickly rebuilding a protective shield for any surviving infected cells.
This is why plantar warts on weight-bearing areas are often more persistent and recur more easily than warts elsewhere on the body.
Why do mosaic warts form separate islands instead of one solid wart?
HPV spreads locally from cell to cell through microscopic breaks in the skin. On the sole of the foot, pressure, friction, and moisture create tiny entry points across a wide area.
Instead of forming one large continuous infection, the virus establishes multiple small colonies wherever it finds a foothold. Each colony then induces surrounding healthy cells to produce keratin, creating a shared protective roof over several distinct viral “islands.”
This is why mosaic warts can appear as scattered lobules, pits, or clusters that are not perfectly contiguous. They are separate colonies growing under one thickened field of skin.
Educational only. This site documents one case history and does not provide medical advice.