What effect does cataphoresis generally have on tissues?

Cataphoresis is an electrical treatment commonly used in esthetics that involves the use of a direct current to drive acidic substances into the skin. This process typically has a hardening effect on the tissues. When acidic solutions are applied during cataphoresis, they cause the tissues to contract, leading to a firmer, possibly tighter skin texture. This reaction is beneficial for certain skin conditions, such as oily or acne-prone skin, where reducing the size of pores and tightening the skin can be advantageous.

In the context of skincare, while other options might relate to different methods or treatments, the primary and most notable outcome of cataphoresis is the hardening of tissues due to the thermal and chemical effects produced by the electrical current and the acidic substances used. This is why the answer highlighting the hardening effect of cataphoresis is considered correct.