Find out the skin care ingredients that counteract themselves

Learn what can happen when two become one.

Here are 5 of such ingredients.

1. Skin Brightening Vitamin-c

Plays well with: Glutathione, peptides, and copper.

"Glutathione is an antioxidant that acts like a battery charger for other antioxidants, including vitamin C, to make them more powerful," says Doris Day, a dermatologist in New York City. "And at night, vitamin C helps skin cells turn over, which works synergistically with wrinkle-smoothing peptides or copper."

Does not play well with: Glycolic acid or salicylic acid. Like an old-school diva, vitamin C melts down so easily and since salicylic and glycolic acids alter the pH of the formulas you mix them with, they'll wipe it out before it has done you any good, says Day.

2. Wrinkle-Brightening, Wrinkle Smoothening Glycolic or Lactic Acids

Plays well with: Green tea and resveratrol.

Unlike vitamin C, these antioxidants are superstable. They brighten skin while the glycolic and lactic acids exfoliate, so you get even more radiance and a more even tone.

When in doubt, "lactic acid is milder than glycolic acid, so it generally mixes well with other ingredients," adds Day.

Does not play well with: Retinol. Pair any of these three ingredients and you could be in for red, peel-y pain.

3. Wrinkle Smoothening, Oil Regulating, Retinol

Plays well with: Hyaluronic acid or glycerin.

"Retinol can penetrate through them, and they moisturize to help minimize the irritation retinol can cause," Day says.

Pick lightweight, hydrating essences or serums, since other ingredients (like occlusives) in heavier creams give retinol a tougher time getting in.

Does not play with: The sun. It's why you're supposed to wear retinol overnight. And if you forgot/passed out, slapping it on in the morning is pointless since the sun breaks down retinol.

4. Benzoyl Peroxide

Plays well with: Salicylic and glycolic acids.

"They exfoliate skin, allowing benzoyl peroxide to penetrate deeper," says Joshua Zeichner, the director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City.

Plus, salicylic acid controls oil production to help prevent new pimples while benzoyl peroxide kills bacteria to shrink existing pimples; for the ultimate one-two punch, layer a benzoyl peroxide spot treatment over a salicylic acid toner. If you get any dryness or irritation, hold off on the benzoyl peroxide for a few days.

Does not play well with: Retinol. It is a little known skin-care fact that retinol and benzoyl peroxide have been shown to render each other utterly useless.

5. Salicylic Acid

Plays well with: Soy, licorice, and anti-inflammatory ingredients.

Botanical brighteners, like soy and licorice, help fade dark spots from past pimples without messing with salicylic acid. And since oily skin is often prone to redness, you can sandwich a soothing serum, between the two.

Does not play well with: Other acids and retinol.

"Retinol helps regulate oil production, but it can be unstable, so use it at night; then use salicylic acid in the morning so you don't deactivate the retinol," says Zeichner. And if a cream lists anything that ends in "acid" on its ingredient list, don't pair it with salicylic acid; it'll definitely irritate your skin.