Substantivity and After-Rinsing Hair Growth Promotion of Cationic Microparticles of Minoxidil

In 2008, researchers Lee, Kim, and Kim studied the effects of cationic minoxidil (MXD) microparticles on hair growth. They found that when these particles were included in a shampoo at concentrations greater than 0.6%, they showed significant substantivity and promoted hair growth in mice. This was in contrast to shampoos with naked MXD microparticles, which did not show these effects. The researchers suggested that despite the MXD particles initially having a negative charge, they could regain their positive charge during rinsing due to the desorption of Sodium Laureth Sulfate (SLES), leading to an ionic interaction with the negatively charged skin and promoting hair growth.