What is the impact of galvanic current on water soluble substances?

The impact of galvanic current on water-soluble substances primarily revolves around their ability to pass through the skin barrier. When galvanic current is applied, it facilitates the movement of ions in the substances, especially water-soluble ones. However, these substances generally have limitations regarding their penetration depth into the skin.

Water-soluble substances lack the lipid solubility that allows for easy transdermal absorption. In the context of galvanic treatments, while the current can assist in moving these substances through the skin's outer layer, it does not mean they will effectively penetrate deep or be absorbed in a way that benefits underlying tissues. Therefore, the assertion that water-soluble substances cannot penetrate into the skin at all underscores the challenge they face, even with current application.

Other choices such as requiring heat, or needing additional chemicals, do not align with the fundamental characteristic of water-soluble substances and their interaction with galvanic currents. Thus, the correct understanding hinges on the nature of these substances and their inherent barriers to absorption through the skin.