What Are Those Ingredients in Your Skin-Care Products?

• Also known as: Ascorbic acid, L-ascorbic acid, ascorbate, magnesium ascorbyl phosphate, ascorbyl palmitate.
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  Good for: All skin types, except very sensitive skin.
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  What it treats: Sun damage, aging.
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  How it works: Vitamin C neutralizes free radicals, which form when the skin is exposed to sun, pollution, cigarette smoke, and other harmful elements. Free radicals damage collagen deep within the skin, causing wrinkles, blotches, and inflammation.
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  RSpicks: Dr. Brandt "C" Gel, $90, dermstore.com. Cellex-C High Potency Serum, $90, drugstore.com.

Perfect skin is hard to come by, but fortunately, concentrated skincare ingredients like salicylic acid exist to better your pores. Because everyone deserves to put their best face forward, we asked aestheticians and dermatologists just what salicylic acid can do to improve one's complexion and safeguard against breakouts.

What is salicylic acid?

Salicylic acid can penetrate the sebum that clogs pores, clearing blackheads. "When used on a regular basis, it can decrease the frequency and severity of acne eruptions," says Leslie Baumann, a professor of dermatology at the University of Miami, in Florida. Avoid it if you have dry or sensitive skin or an allergy to aspirin. (It's in the same family as the pain reliever.)

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How does salicylic acid work exactly?

The fast-acting acid is best known for treating common acne that’s caused by clogged pores, especially for those with oily or combination skin. But salicylic acid can do so much more than just dry up pimples, says Dr. Jennifer Segal of Metropolitan Dermatology Institute in Houston. “It can treat a variety of conditions, including acne, warts, dry skin, and even dandruff.”

What products can I find salicylic acid in?

Salicylic acid face washes, such as Dermalogica Clearing Skin Wash ($39; sephora.com) prevent breakouts before they start by dissolving oil, dirt and other debris. But, if your acne or breakout is severe enough that you want to treat it around the clock, salicylic acid gels are ideal. The consistency of spot treatments like Alba Botanica Anecdote Maximum Strength Invisible Treatment Gel ($5; amazon.com) is generally lightweight enough to be worn under makeup, and can be applied to clean skin overnight.

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How often should salicylic acid be used to see its effects?

As unbelievable as it sounds, salicylic acid spot treatments can improve or even eliminate pimples overnight. (Yes, really.) However, that depends on the severity of your breakout, and as a general rule, spot treatments should only be used when necessary.

Does salicylic acid work on all skin types?

While salicylic acid really gets the skin-clearing job done, the ingredient can have adverse side effects, such as minor skin irritation, rashes, or peeling. While it's ideal for oily or combination skin types, it can be used for those with normal skin who experience the occasional breakout. If you have dry or sensitive skin, steer clear of the acid, as your pores may become too agitated with use.

As with any skincare ingredient, it’s important to exercise caution when using salicylic acid. Don’t apply too much product until you know just how your skin will react. It’s also wise to avoid applying it to skin that is already irritated or sunburned.

“The ability of salicylic acid to induce irritation limits its use," says Dr. Segal. "It's important to make sure that the other products in your routine, such as your cleanser, moisturizer and sunscreen, are gentle and soothing.”

While it's extremely rare, salicylic acid can cause a serious allergic reaction among some users. Symptoms of this include itching, hives, light-headedness and swelling. If you experience any of these, please consult a physician as soon as possible. It’s also not an appropriate treatment for every type of acne. “If acne vulgaris (common acne) is confused with acne rosacea (breakouts in sensitive skin), using salicylic acid only further irritates the skin and worsens rosacea,” Dr. Segal warns.

Dermalogica Clearing Skin Wash with Salicylic Acid

To buy: $39; sephora.com.

• Also known as: 4-hydroxy-3-methoxycinnamic acid.
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  Good for: Dry skin, normal skin.
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  What it treats: Sun damage, aging.
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  How it works: Usually combined with vitamins C and E, "ferulic acid helps stabilize them," says Barbara R. Reed, a clinical professor of dermatology at the University of Colorado Health Science Center, in Denver. This doubles their power as sun-protective agents and boosts their ability to neutralize free radicals.
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  RSpick: SkinCeuticals CE Ferulic serum, $135, skinceuticals.com for store locations.

• Also known as: Ubiquinone, coenzyme Q-10.
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  Good for: All skin types.
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  What it treats: Sun damage, irritation, aging.
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  How it works: Idebenone is one of the strongest antioxidants contained in cosmetics. Its anti-inflammatory properties "help preserve collagen and elastin," which give the skin support and resilience, says Lisa Donofrio, an associate clinical professor of dermatology at the Yale University School of Medicine.
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  RSpicks: Priori Radical Defense, $120, prioriskincare.com for stores. Elizabeth Arden Prevage Anti-Aging Treatment, $155, elizabetharden.com.

It’s nearly impossible to scroll through Instagram or browse the ever-crowded Sephora aisles without reading about hyaluronic acid. The skin-boosting beauty staple has attracted more and more fans in recent years, and it's now a highly sought after anti-aging ingredient found in everything from serums to moisturizers. But what exactly makes this popular anti-ager better than the rest? We asked dermatologists to weigh in on the benefits of hyaluronic acid, and how it works to better even the most sensitive of complexions.

What is hyaluronic acid?

Sodium hyaluronate, or hyaluronic acid, naturally occurs in our bodies, and it works to both attract and seal water into the skin. "The greatest amounts of hyaluronic acid are found in skin soft tissue and the eyes,” says Dr. Payman Danielpour of Beverly Hills Plastic Surgery Group. "Our bodies naturally produce the substance to draw in and retain water to keep the body well lubricated and moist." Used topically and as an injectable, hyaluronic acid is commonly used as a filler in cosmetic surgery to plump lips, cheeks, and fine lines.

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How does hyaluronic acid work exactly?

Hyaluronic acid works by drawing in moisture to give your skin a smooth, and almost plumped out appearance, making fine lines and wrinkles less prominent. "When you hydrate the skin from outside, you make fine lines less noticeable," says Susan Weinkle, an assistant clinical professor of dermatology at the University of South Florida, in Tampa.

Just a single gram of hyaluronic acid can hold up to six liters of water. “Currently, there is a substantial amount of research being done on the use of hyaluronic acid to combat and prevent the effects of aging,” notes Dr. Danielpour. For example, one study showed that as a result of aging over time, there is a progressive reduction of the size of the hyaluronic acid polymers in the skin. This explains why skin loses moisture and feels physically dryer as we age.

However, aging isn’t the only reason for the body’s reduction in hyaluronic acid. Exposure to ultraviolet radiation from the sun, pollution, and tobacco smoke are key factors in hyaluronic acid depletion.

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Does hyaluronic acid work on all skin types?

Although hyaluronic acid is beneficial for all skin types, the miracle, moisture-boosting ingredient is especially helpful for those with sensitive or dry skin, since the acid boasts skin smoothing and hydrating properties.

What products can I find hyaluronic acid in?

You can find hyaluronic acid in a variety of skincare products, including moisturizers and serums. Expert esthetician Shani Darden, who counts A-list celebs like Jessica Alba as clients, likes applying a hyaluronic serum before an everyday moisturizer. “I love to pair a deeply hydrating hyaluronic acid serum that plumps the skin, like Dr. Nigma’s Serum No 1 ($185; net-a-porter.com), with my Daily Oil-Free Moisturizer ($42; shanidarden.com) for deeply hydrated, plump skin,” Darden says.

Hyaluronic acid-infused moisturizers also exist, including Neutrogena Hydro Boost Hyaluronic Acid Hydrating Water Face Gel Moisturizer ($17; amazon.com) and the top-rated PCA Skin Hyaluronic Acid Boosting Serum ($115; dermstore.com).

How often should hyaluronic acid be used to see its effects?

Hyaluronic acid is safe to use every day, and works best when applied to wet skin after cleansing.

PCA Skin Hyaluronic Acid Boosting Serum

To buy: $115 for 1-ounce; dermstore.com.

• Also known as: Epigallocatechin gallate (EGCG).
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  Good for: All skin types.
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  What it treats: Sun damage, irritation, aging.
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  How it works: "Green tea is one of the most potent forms of photo-protection," says Patricia Farris, a clinical assistant professor of dermatology at Tulane University, in New Orleans. "It protects against sun damage, and studies have shown that a product containing at least 5 percent green-tea extract may help prevent skin cancer" when applied before sun exposure along with sunscreen.
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  RSpick: Kinerase Gentle Daily Cleanser, $33, kinerase.com.

• Also known as: Nicotinamide.
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  Good for: Dry skin.
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  What it treats: Sun damage, irritation, aging.
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  How it works: "Niacinamide stimulates microcirculation and prevents water loss in the skin," says Reed. Additionally, says Donofrio, "deep in the skin, it increases production of ceramides, which are the glue that holds the cells together and prevents water loss." So it helps to hydrate, too. Translation: It gives skin a healthy, youthful glow.
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  RSpicks: Olay Regenerist Micro Sculpting Cream, $27 at drugstores. Luzern Serum Rosacea Care Absolut, $75, luzernlabs.com.

• Also known as: Lipoic acid.
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  Good for: All skin types, except very sensitive skin.
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  What it treats: Sun damage, aging.
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  How it works: Alpha lipoic acid "helps with exfoliation and the stimulation of collagen, which may lead to a smoother appearance of the skin," says Ronald R. Brancaccio, a clinical professor of dermatology at the New York University School of Medicine, in New York City. Since it's a powerful exfoliator, avoid it if your skin is sensitive or prone to redness.
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  RSpicks: N.V. Perricone M.D. Advanced Eye Area Therapy, $95, perriconemd.com. Aubrey Organics Rosa Mosqueta Night Creme, $23.50, aubrey-organics.com.