Since acne is widespread and typical during adolescence, the public doesn't seem to realize there's as much science underlying its causes as any other medical condition; furthermore, since acne isn't life threatening, the public seems to be content with vague hearsay like "just wash more" or "maybe it's something you're eating."

As anyone who's suffered from moderate to severe acne will attest, it's every much as socially and psychologically debilitating as any other condition.

The scientifically-proven causes of acne are:
1) Increased Oil Production
2) Growth of Acne Bacteria
3) Keratinization of the Pore
4) Inflammation

These factors are interrelated. For example, increased oil production provides more food for acne bacteria, and increased acne bacteria lead to inflammation.

It's important to understand that small amounts of acne bacteria live in our pores from early adolescence till old age, and skin oil production occurs inside the sebaceous glands of the skin. In other words, breakouts aren't caused by "catching" acne bacteria from someone else, and it isn't caused by oil or dirt being "absorbed" by the skin.

Lets use common sense to determine the real causes of acne:

If acne was really caused by "dirt", why does the face typically have more acne than the feet. We walk outside barefooted and leave our feet in sweaty socks all day. (The reason acne occurs more on the face is due to the high number of sebaceous glands in the face relative to the rest of the body.)

If acne was caused by dirt, we would expect people in third world countries, who dont have consistent access to soap and water, to have severe acne problems; however, in all the research I've read, I've never heard this to be the case.

Guys who deal with grease like mechanics and cooks don't seem to have more acne than anyone else, but teenagers in high school who never deal with oil or grease have constant breakouts. Even the adult cooks in fast food restaurants don't seem to have particularly bad acne, so how can fast food be a cause?

Finally, two personal examples: As an adult, I eat much more fast food than I did as a teen, but my acne is better. Also, as an adult, I wash my face much less vigorously now than I did as a teen, but my acne is better. Of course, these examples are just one person and anecdotal, but I believe the truth of the principle behind these examples is readily apparent.