Have this to shout to verruca hosts: DUCK TAPE!!!
I developed a whole bunch of these on my foot last year (suspect I picked them up in a shower when I'd been camping - had never had them before and this was the only exposure my plates ever got to communal facilities). I read about the duck tape treatment after googling but was extremely
as I'd never had much luck with alternative treatments for anything in the past.
Just shove little patches of tape on the blighters and replace it when it becomes unstuck. The centre of the verruca gets soft - I'd gently scrape the soft bits out with the pointy end of a metal nail file. I persisted for about six weeks and eventually the wretched things disappeared for good. I was amazed and gratified. Keeping my toes crossed they'll stay away.
Plenty of people said this hadn't worked for them, but it's surely worth a try - duck tape is cheap, the treatment is not messy, and it doesn't take up much of your time.