I've had constant moderate acne for about 8 years and I've tried a lot of different products. Most of them were quite expensive, and very few of them made any difference in my skin. Ironically the most effective thing is just about dirt cheap and has been sitting in my house all this time.
Why salt? Salt is a natural anti-bacterial. Its been used as a healing agent throughout history, and our bodies simply could not survive without it. Note: table salt is stripped of most of its healing minerals, and therefor may not be as effective. Sea salt, or salt crystals, is best.
I read about using salt masks to treat acne a few weeks ago. I started using it in the mornings as a cleanser/scrub, and when I can I'll use it as a mask in the evening. It can also be used as a toner over night, and as a body scrub if you have body acne (and even if you don't).
You can adjust the amount you use to whatever your skin needs, but I use
-1/2 teaspoon sea salt
-1 teaspoon water (warm preferably)
I mix this together in a small bowl, soak it into the cotton ball and gently scrub it on my face. The first few times I used this it stung after a few minutes so I washed it off quickly, but after a few weeks it doesn't sting anymore and I can leave it on for a long time if I want a more intense treatment. If it stings a lot or you have sensitive skin use less salt in the beginning and wash it off sooner. Right after using the salt your skin will be a little red, but that's natural after using an exfoliant.
For overnight let the salt dissolve in hot water and apply it like you would a toner or put it in a spray bottle to spritz on your face. In the bath add half a cup to treat body acne (use moisturizer after). I also love adding this to St Ives apricot scrub, aloe vera gel, and a few drops of olive oil and scrubbing my skin (I do it quite hard) to make it super soft.
After 3-4 weeks of doing this my skin has improved a lot. I have very few breakouts, my skin tone is much more even, and my face is so much softer. Using it in the morning makes my foundation look better too. I'll need a few more weeks to see if this is 100% effective as my acne has good/bad cycles but so far I've seen good things and would recommend everyone try it.
To read more about the internal health benefits of salt visit WorldWideHealth.com