A white substance on the glans that falls off as soon as you rub it indicates that there is significant inflammation on the glans, which means there is foreskin scale. The vast majority of many people have long foreskin, usually do not turn the foreskin over every day to clean, the inner plate of the foreskin has secretion, secretion will be attached to the foreskin and glans. This secretion collects more, a rub will have a lot of foreskin scale, long time gathering increase, it will lead to foreskin scale deposited on the glans. Long-term chronic inflammatory stimulation can easily lead to increased incidence of prepuce glansitis or penile cancer. It is recommended to wash clean and keep dry every day to prevent causing penile cancer.