During a facial treatment, the negative pole of the galvanic current machine may be used on the skin to:

The use of the negative pole of the galvanic current machine during a facial treatment is primarily associated with stimulating nerves and promoting various beneficial skin and tissue responses. Galvanic current is known for its effects on skin tissue, which include enhancing blood circulation and improving cellular activity. When the negative pole is applied, it creates a negative charge that can energize nerve endings, leading to stimulation of the underlying tissues.

In contrast, the other choices focus on different effects that are achieved through various methods rather than specifically through the use of the negative pole of galvanic current. For instance, calming redness often involves the use of soothing ingredients or techniques that directly address inflammation rather than electrical stimulation. Softening the skin, while it may occur as a result of increased circulation from galvanic treatment, is not the primary role of the negative pole. Hydration is also typically achieved through products applied to the skin rather than primarily through the application of galvanic current. Thus, the primary action of using the negative pole in galvanic treatments aligns best with the stimulation of nerves.