The bottle causes everything on the nails to be transferred to its interior. The contamination of the nail polish is due to the brush catching and inoculating everything it encounters on the nails, between multiple people's hands and feet, into the bottle. Unlike traditional nail polishes, LACTUBE™ is never contaminated by external agents or previous applications thanks to a special valve that prevents any backflow, and at the end of the treatment, the bristles in contact with the nails are quickly replaced. Goodbye bad surprises!