The idea that there’s acid in your skin-care products may sound scary. In reality, they’re game-changers in the quest to achieve smooth, even-toned, and radiant skin.

These acids may be alpha hydroxy acids or AHAs (like glycolic or lactic), beta hydroxy acid or BHA (like salicylic), or act as skin brighteners (like ellagic) to chase away dark spots from too much sun exposure.

Knowing exactly what acids are in your products and how they work can help you find the right mix of anti-agers to build the routine that delivers the results you’re after. This guide is meant to help you understand the most common types of acids and what they do. We’ll also offer dermatologist-recommended products that feature them. Get ready to glow!

Ascorbic Acid

This is probably the best-known acid: It’s vitamin C. It’s one ingredient consistently recommended by dermatologists. “There is extensive published research showing that vitamin C can be effective in anti-aging,” says Deirdre Hooper, MD, a board-certified dermatologist at Audubon Dermatology in New Orleans.

For one thing, it’s an antioxidant (meaning it protects skin from environmental assaults like pollution), inhibits pigment production, and stimulates collagen, notes a study published in October 2014 in the Journal of Drugs in Dermatology.

That said, “vitamin C has the potential to be powerful [only] if formulated and packaged correctly,” Dr. Hooper says. Ascorbic acid can easily become unstable when exposed to light.

She recommends SkinCeuticals or SkinMedica brand as two that have research supporting the efficacy of their products.

Try SkinMedica Vitamin C + E Complex, $102, Dermstore.com.

Azelaic Acid

Derived from a yeast, azelaic acid is a go-to for addressing dark spots, and a review published in August 2014 in the Journal of Clinical and Aesthetic Dermatology suggests it’s also effective in treating melasma. (Melasma is a condition marked by darkened patches of skin that’s often triggered by sun exposure during pregnancy, notes Harvard Medical School.)

It’s more than just an exfoliator, though. “Azelaic interrupts the pigment process in skin,” says Noelani Gonzalez, MD, an instructor in dermatology at Mount Sinai in New York City. Specifically, the ingredient inhibits the enzyme tyrosinase, which is involved in melanin production. With decreased pigment creation, discoloration disappears over time. If you have rosacea, your dermatologist may also recommend topically treating with azelaic, as it’s a potent anti-inflammatory that decreases redness and swelling, according to MedlinePlus.

Try Philosophy The Microdelivery Triple-Acid Brightening Peel, $70, Sephora.com.

Ellagic Acid

Scientists get this plant compound from berries, pomegranate, or nuts. Like azelaic, it’s a known skin brightener. In fact, in a study published in the Journal of Drugs in Dermatology, a combination topical containing 0.5 percent ellagic and 0.1 percent salicylic acid was just as effective in reducing pigmentation as a 4 percent hydroquinone product. Hydroquinone has been considered the gold standard topical for treating dark spots, but there are concerns over potential side effects like dryness and irritation. For that reason, many people want to turn to alternative but just-as-effective options, like ellagic acid.

Try Glamglow FLASHMUD Brightening Treatment Mask, $59, Sephora.com.

Ferulic Acid

Often, you’ll see ferulic paired with vitamin C. “Ferulic stabilizes vitamin C,” says Hooper. (Vitamin E is another stabilizer for C.) Here’s why: Per past research, vitamin C is an antioxidant, a substance that protects skin from free radicals, which are molecules that damage cells and contribute to skin aging.

“Antioxidants are looking for free radicals, and the world is full of them. As soon as they come into contact with pollution or UV light, they’re oxidized,” she explains. Meaning: without a stabilizing ingredient like ferulic, C would be rendered ineffective the first time you opened the bottle and used the product.

Ferulic doesn’t just play a supporting role. It’s an antioxidant itself that protects collagen and elastin structures in skin and reduces the production of pigment (to lighten dark spots), notes a review from October 2018 in Skin Pharmacology and Physiology.

Try SkinCeuticals C E Ferulic, $166, Dermstore.com.

Glycolic Acid

Glycolic acid is an AHA derived from sugarcane that can be found in cleansers, serums, treatments (like masks), and moisturizers, according to an article published in April 2018 in Molecules. Because glycolic acid can penetrate the outer layer of skin and increase cell turnover, it’s an effective exfoliator and can play a variety of roles in your routine, says Brooke Sikora, MD, a dermatologist in Chestnut Hill, Massachusetts.

If you’re dealing with both acne and skin aging, glycolic is for you, suggests an article published in the January–February 2019 issue of the Brazilian journal ABD. “This is an ingredient that can kill two birds with one stone,” Dr. Sikora says. “Glycolic is especially good as a treatment for addressing both acne-prone skin and hyperpigmentation. When you can address multiple skin concerns with one product, you can save money and time.” Glycolic is most effective when left on skin. Rather than using a glycolic cleanser, she recommends a lotion with glycolic acid.

Try Drunk Elephant T.L.C. Framboos Glycolic Resurfacing Night Serum, $90, Sephora.com.

RELATED: 10 Home Remedies for Dry Skin

Hyaluronic Acid

You’ll find hyaluronic acid (HA) pumped into moisturizers and anti-aging creams for its skin-smoothing properties. It’s certainly effective: HA, a natural component of skin, draws water from the environment and can trap 1,000 times its weight in water, according to a review published in December 2018 in the International Journal of Biological Macromolecules.

When applied, the ingredient plumps up the outer layer of skin cells to soften lines and enhance a glow, says Sikora. That said, there’s only so much it can do. “HA is too big of a molecule to reach the dermis [the deeper layer of skin], so it doesn’t stimulate collagen production,” she says.

Try Neutrogena Hydro Boost Hydrating Water Gel With Sunscreen, $14.97, Amazon.com.

Kojic Acid

The process of fungus fermentation produces kojic acid. Because kojic acid inhibits tyrosinase (which is responsible for producing melanin, the pigment present in skin), it’s added to products that claim to brighten skin and rev radiance. But, as a small study published in December 2014 in Photodermatology, Photoimmunology, and Photomedicine suggests, it’s not as effective as hydroquinone (HQ).

Try PCA Skin Pigment Gel HQ Free, $60, Dermstore.com.

Lactic Acid

This AHA is derived from fermented milk, according to a study published in April 2018 in Molecules. “Lactic acid is the only AHA that’s both moisturizing and an exfoliant,” says Dr. Gonzalez. Because it hydrates simultaneously, it tends to be gentler, she says. (This may be because lactic acid is present in the gut bacteria.) Yet because it’s so mild, dermatologists like Gonzalez use it less on the face and more on the body. Where it shines is in body lotions designed to treat dry skin, flaky feet, or keratosis pilaris, she says. Keratosis pilaris shows up as bumps, often on the backs of the arms, notes the Mayo Clinic.

Try AmLactin 12% Moisturizing Lotion, $17.99, Amazon.com.

Mandelic Acid

Another acid in the AHA category, mandelic acid is an extract of bitter almonds that has gentle exfoliation properties, according to the skin-care product website Dermstore. Because it slowly penetrates skin, as a past study notes, people find that mandelic is less irritating than other acids, even for sensitive skin types.

Mandelic is also oil-loving, which means it can help regulate sebum production.

And it’s an anti-ager. In a small study on 24 middle-aged adults, applying a mandelic acid product to skin twice a day for four weeks improved skin firmness by 24 percent, per the paper, which was published in December 2018 in the journal Facial Plastic Surgery.

Try The Ordinary Mandelic Acid 10% + HA, $6.80, Sephora.com.

Phytic Acid

Legumes and seeds are the source of this AHA with antioxidant properties, according to the skin-care company SkinCeuticals. “What’s common about these AHA ingredients is that they’re good at resurfacing the surface of skin to smooth texture,” says Hooper.

Glycolic is the most well studied acid, she says, so it’s unclear how these other AHAs compare with one another.

Try Kate Somerville Liquid ExfoliKate Triple Acid Resurfacing Treatment, $58, Sephora.com.

Salicylic Acid

Salicylic belongs to a category called BHAs. You probably know salicylic as an acne fighter — and it is. “Salicylic exfoliates the outer layer of skin. It’s lipid soluble, so it can also penetrate deeper into the pores, where it helps get rid of debris and buildup,” says Gonzalez. This helps unclog pores to prevent breakouts. For acne, she recommends using a cleanser containing salicylic acid once a day to treat breakouts.

Try Neutrogena Oil-Free Salicylic Acid Pink Grapefruit Cleansing Acne Wash, $7.97, Amazon.com.

What to Keep in Mind When Using Acids on Your Skin

Topical application of some acids can make skin sensitive to the sun, past research suggests, so be sure to wear a broad-spectrum sunscreen every morning to protect your complexion. Also keep in mind that this is an extensive list of acids that play different roles in skin. Your dermatologist can help you identify which ones are best for your skin type and concern. “You can waste a lot of money DIYing your beauty routine,” says Hooper.

Along with talking to your dermatologist or messaging dermatologists through social media (truly!), she recommends making the American Academy of Dermatology and American Society for Dermatologic Surgery your go-to resources for skin-care research.