Similar to real-life couples, some ingredient pairs in skin-care products are a perfect match—while others should really call it quits. "Multitasking products eliminate a few steps and can save you money, but combining several active ingredients may be ineffective or even irritating," says Dendy Engelman, M.D., a New York City dermatologist. This is especially relevant now, thanks to the rise of BBs and CCs—creams that promise to. . .well, what don't they promise to do? (Think: nix zits, fade spots, smooth lines, ward off UV rays, and offer a color tint.) Read on to discover which ingredients are destined for a harmonious marriage.

Made for Each Other
These ingredients not only get along splendidly, but may even help each other perform better. Stock up!

In addition to leaving skin burned and wounded, the sun's ultraviolet rays spike free-radical damage in the skin, which can accelerate aging. "Antioxidants help amplify the protective benefits of sunscreen by warding off free-radical damage that sunscreen itself can't block completely," says Fredric Brandt, M.D., a New York City dermatologist. Vitamin C, grape-seed polyphenols, and green tea pack the most photoprotection. Try Murad Essential C Day Moisture Broad Spectrum SPF 30 ($60, at Sephora).

When To Apply: In the morning, under your makeup.

Wrinkles and acne? Lucky you. But don't freak, because this acid combo is supereffective at knocking out both. "Beta hydroxy acids (or salicylic acid) exfoliate dead skin cells and dissolve in oil to help unclog pores, which then lets alpha hydroxy acids (or glycolic acids) dig deeper to stimulate collagen production and plump fine lines," says Noelle Sherber, M.D., a dermatologist in Washington, D.C. So although they work great separately, they're more powerful combined. Try Peter Thomas Roth AHA/BHA Acne Clearing Gel ($45, peterthomasroth.com)

When To Apply: At night, after cleansing.

A good wingman for retinol? Hyaluronic acid (HA). Because it draws and then seals water to the skin, HA can help offset the potentially drying effects of the retinol, says Engelman (although those with superdry skin may still need to slather on a separate moisturizer). While the stuff naturally occurs in the skin (yay!), it plummets as you age (boo!)—a process that makes fine lines appear more pronounced. That's why adding HA to your retinol can also make skin look plump and youthful. Try Vichy LiftActiv Retinol HA Concentrate ($55, vichyusa.com).

When To Apply: At night, after cleansing. (While new retinol formulations are photostable—meaning they don't become inactive in the sunlight—heat and UV light can still make them irritating to skin.)

Smearing on a dark-spot buster and skipping sunscreen (or using one with less than SPF 30) is like drinking a milk shake during a workout: It obliterates the hard work you've put in. Avoid a one-step-forward-two-steps-back approach by using a combination product like Dermalogica Pure Light SPF30 ($60, dermalogica.com), which contains spot-lightening vitamin C and SPF (plus other antioxidants for even more protection).

When To Apply: In the morning.

Salicylic acid and benzoyl peroxide—the two most widely used acne-zapping ingredients—are your zits' biggest enemies. But what makes them potent enough to dry up and clear out spots can also make surrounding skin pretty angry too. "Polyphenols like green tea and grape-derived antioxidants help offset redness, dryness, and peeling that strong acne treatments can cause," says Sherber. Try Neutrogena Oil-Free Acne Stress Control Power Foam Wash ($7.49, at drugstores), which has salicylic acid and green tea.

When To Apply: Morning and night.

A little skin-care 101: Prolonged skin inflammation can accelerate aging. So if you're currently using a line-smoothing retinol and want to supercharge your results, don't up your dosage. Instead, put some pep(tide) in your products. "Peptides—like retinols—improve collagen production but won't cause irritation. Combining them with retinols can offer a gentle but effective anti-aging boost," says Paul Jarrod Frank, M.D., a clinical assistant professor of dermatology at NYU Medical Center. SkinMedica Retinol Complex 1.0 ($90, skinmedica.com for locations) combines these ingredients.

When To Apply: At night. Top with a moisturizer.