Papillomas are small raised bumps which typically develop on the skin and are also known has warts (Verruca Pedis). It has been found that they majority of papillomas’ are caused by the human papillomaviruses (HPVs). Children are often at risk of develop papillomas’ due to direct contact with another individual’s wart, using public showers and swimming pools, not wearing shoes or thongs in public places and a compromised immune system. More often than not papillomas’ will develop on the feet, knees and hands.
References: http://www.northmelbournepodiatry.com.au/content.php?id=Plantar_warts_papillomas_verrucas
https://www.healthgrades.com/right-care/skin-hair-and-nails/papilloma–causes