Flat warts (verruca plana) are small, slightly raised bumps that appear in clusters. They're caused by the human papillomavirus (HPV), a group of more than 100 viral strains. HPV is the most ...

Ask around your friends or colleagues if anyone has a wart, and those who will admit to it will be rare. A verruca? Maybe a few will confess – although more likely to a past affliction as a ...