For most people, a.k.a. the 99.9 percent of the population without flawless complexions, skin can be a mystery. One day it's glowing and gorgeous, and the next day it's behaving like an unruly teenager going through puberty. And deciphering all of the spots and marks that pop up over time is no small task. So we called in the professionals. Today Dr. Joshua Zeichner, Director of Cosmetic and Clinical Research in Dermatology at Mount Sinai Medical Center, is here to tell us everything we need to know about those mysterious skin spots and scars.

Ready for the cold hard facts? Ok, here's the first truth bomb: Not all acne scars are truly acne scars. Dr. Zeichner offers this simple test - the foundation test - all you have to do is apply face makeup and look in the mirror. "Scars are raised or depressed spots that makeup will not cover. Brown or red spots that can be covered are not truly acne scars." Now that you know what's what, let's dive a little deeper.

Red Spots

If you're seeing red spots, Dr. Zeichner says you're seeing dilated blood vessels that develop as a result of a pimple. As eternal as they may seem, red spots are not permanent and will eventually go away. Your best bet is to cover these suckers with concealer and continue to treat the spots as blemishes in the healing stage.

Brown Spots

Brown spots are actually stains in the skin. According to Dr. Zeichner, "The skin remembers there was inflammation there and revs up pigment production." This pigmentation fades with time, but these spots are stubborn and it could take several months or more. In-office peels and laser treatments will lighten brown spots. At-home, look for products with skin-brightening ingredients like vitamin C, hydroquinone, kojic acid and soy.

Depressed and Raised Scars

Depressed acne scars can range from the deep icepick variety to shallow, broad scars, but they're all "caused by abnormal collagen resulting from inflammation," says Dr. Zeichner. Serious scars may call for laser resurfacing to see real results, but skincare ingredients, such as peptides and retinols, which promote the formation of collagen, will benefit the skin too. Raised scars pose the opposite problem. Dr. Zeichner recommends injecting these scars with cortisone to flatten them out.

Do you have any skin concerns you would like a dermatologist to weigh in on? Leave them in the comments below and we'll see if our experts can help.

Photos: Thinkstock