The Myth: Using more of a product will make it work faster.
The Truth: "In most cases, heaping on a skin-care product is only going to land you in the dermatologist's office faster,"; says Kenneth Beer, a dermatologist in Palm Beach, Florida. "Anything that contains an active ingredient will irritate your skin if you overdo it." The most common active ones are vitamin C, retinol, and alpha hydroxy acids (like glycolic), which work to smooth the skin and soften lines, and beta-hydroxy acids (like salicylic) and benzoyl peroxide, which clear breakouts. If you're using something that contains these ingredients, apply just enough to barely cover the area you're treating. If you're using a retinol cream, for example, a pea-size dab will do the trick.
The Truth: "Ninety percent of people using toners shouldn't be," says Ranella Hirsch, a dermatologist in Cambridge, Massachusetts. "In most cases, they strip the skin of the oil it needs to stay soft." Just cleansing is enough to remove surface dirt and oils.

But what about that dark stuff you see on the cotton ball after you cleanse? It's not dirt. It's healthy oils that darken when exposed to air. So who should use a toner? Only people with very oily or acne-prone skin. If this is you, look for one with alcohol and salicylic acid to fight breakouts.