If I may add another comment to my post. When I lived in Europe (1980s) and worked for a Dutch and German firm (cosmetic devices), the German “Stiftung Warentest” examined galvanic DC devices that were, at the time, widely used by European estheticians.

The claim was that “products would be ‘pushed’ deeper into the skin, thus making such products more effective.” The study found that, indeed, cosmetic preparations did penetrate more deeply into the skin … HOWEVER; trace amounts of chemicals from these preparations were FOUND IN THE BLOOD! Because of the blood-test findings, these DC devices were banned in Germany. I do not know the current status of such devices in Europe or Germany. They were (and are) ubiquitous.

I think a much more important issues here is just exactly WHAT is in those “cosmetic preparations” … and what (if anything) is entering your blood? I think that’s a much greater (long-term) concern. (BTW, you can get excellent results using only baking soda and the negative pole: to soften blackheads.)
** Oh, and “being protected by the FDA?” From my point of view, there is no FDA any more!

I have absolutely no involvement with any manufacturer or cosmetic product. (“DC” in my name, is the current; I’m NOT a chiropractor!) My take is that these little devices are designed to sell cosmetic products … and, that’s where the real money is made!

I hope I have been helpful!