One's definition of hygiene standards though can depend. I mean yeah we didn't always have soap and yes I know it's thousands of years old, but we probably didn't you know do more than splash water on our faces when we were cavemen

Possibly.

The book I mentioned discusses biomes. A other good book on microviolws is I Contain Multitudes

I also suspect that over time, what microbes cause microbial caused acne has changed or drifted.

Edit; sensitivities to chemicals and such in soaps can also cause acne, as per the other posters' inflammation cause.

I agree. That's why I said Most As per the dermatologist who wrote the book I mentioned. :)

It's probably been around since prehistoric times, although the main cause of outbreaks has probably changed.

In the book The remarkable life of the skin, the author mentions about how the majority of acne is caused by microbes outbreaks in the side the pores of the skin. And we probably had bacteria and other stuff in our skin back then. While we do have better hygiene standards these days, we probably also have more pollutants etc that balance it out.