I've had acne in my face and chest a good portion of my life...
Acne is when zits form. Zits form because they are clogged up, inflate and become infected and then produce a white or black head.
You can do many things:
Use a Peroxide Benzoil bar soap (this peroxide is found in ALL acne treatment products, minus all the chemical ****). This cleans your pores and reduces the amount sebum oil your skin produces - two birds one stone. Sebum oil is what makes your pores inflate once they are clogged up and this oil is natural, you want to control it and not completely get rid of it since it keeps your skin moist and healthy.
See a doctor, mine prescribed me a pill called Minocin which fights infection and acne. He told me that before having to consult a dermatologist - he had to try this basic treatment first and it worked wonders for me.
Causes can range from sweat, genetics, skin disease, sun exposure, stress (biggest factor), nutrition, touching the skin on the face too often without washing your hands...and the list goes on...
IMO, some people make it too complicated - it's basic stuff, it can be inconvenient to do all this crap every day, but once you do it and are consistent it goes away.
When working with acne, you can't afford to try something different every week or month - this will make it a lot worse. Your skin is like muscles it needs a while to adapt to what you are doing to it. To see results you need to stay on treatments for a while before seeing any results.
As for the herbal stuff - I've always read that using natural things is always much better.
Hope this helped.
Eric