Verrucas are caused by a viral infection of the skin on the feet, specifically by certain types of the human papillomavirus (HPV). The virus enters through tiny breaks in the skin, typically in warm, moist, shared environments like swimming pools and communal showers.

What verrucas are

  • A verruca is a type of wart that appears on the sole (plantar surface) of the foot.
  • They often look like small, rough, sometimes “cauliflower‑like” patches with tiny black dots (clotted capillaries) in the centre.
  • Because they are on weight‑bearing areas, the pressure can push them inward, making them feel sore or like a stone in the shoe.

The main cause: HPV

  • Verrucas are caused by infection with HPV strains that prefer the skin of the feet (for example types 1, 2, 4, 27 and 57).
  • The virus causes the skin cells to overgrow and thicken, forming the characteristic hard lump of a wart.

How the virus gets in

  • HPV needs a way into the skin, usually via tiny cuts, abrasions or softened, “soggy” skin.
  • Common exposure spots include:
    • Swimming pools and poolside areas
    • Communal showers and changing rooms
    • Gym floors or saunas where people walk barefoot
  • The virus can spread:
    • By direct skin‑to‑skin contact with a wart or verruca
    • Indirectly, by walking on contaminated surfaces or sharing items like towels or socks.

Why some people get them more

  • People with weakened immune systems (for example due to certain illnesses, chemotherapy, or immune‑suppressing medicines) are more prone to verrucas and may have more persistent lesions.
  • Children and teenagers are commonly affected because their immune systems are still maturing and they often go barefoot in communal areas.
  • Frequent barefoot walking in public wet areas increases the chance of the virus entering the skin.

What does not “cause” verrucas

  • Poor hygiene alone does not create a verruca; HPV exposure plus a route into the skin is required.
  • They are not caused by “bad blood” or systemic toxins; the problem is localised viral infection in the upper layers of the skin.

If a verruca is painful, spreading, or not improving over time, a pharmacist, podiatrist, or GP can advise on treatment options and check that it really is a verruca.