Glycolic acid is potentially dangerous if used incorrectly or at too high a potency. You want to shoot for a product that is around 30% glycolic acid by volume. More risks damage, less risks no significant effect. The pH of the solution ought to be around 2 or 2.5. Again, lower pH risks damage, higher pH risks no significant effect.

There’s actually a big difference between a pH of 2 and a pH of 2.5. The pH scale is logarithmic, so half-increments actually differ by a multiple of the square root of 10, which is about 3.2. So a pH of 2 is actually about 3.2 times more acidic than a pH of 2.5. A pH of 1 is 10 times more acidic than a pH of 2, about 32 times more acidic than a pH of 2.5, and 100 times more acidic than a pH of 3.

You may want to avoid salicylic acid, since it actually makes your skin more sensitive to sunlight. In extreme cases it can induce hyperpigmentation, which is not nearly as easy to get rid of as it is to cause. Pyrithione zinc, the main ingredient in most dandruff shampoos, works just as well and doesn’t cause photosensitivity. It’s actually a potent antiseptic, working equally well on bacteria and fungi. Some such shampoos also contain salicylic acid, but these days it’s more the exception than the rule. The leading brands do not.

A small minority of people are allergic to pyrithione zinc, so if you’ve never used it before, be sure to try a small amount on a test patch of skin and watch for swelling.

I remember finding the solution to acne very quickly: Just be clean. This includes what your skin touches on daily basis and what you put into your body. You attitude is also a factor: having a bad temper or negative attitude makes a pretty toxic environment for your body. Notice how when you get stressed out you also get breakouts.

Anyway, if I sweated, I changed my clothes and showered. No fake shampoos or soaps. Only real stuff.