By now you've probably heard of 42 retinol, the skin-care ingredient that promises to smooth fine lines and wrinkles, shrink pores, clear up acne, and even out skin tone. Dermatologists swear by it for patients young and old, touting its countless benefits and uses, and studies support its wide-ranging abilities. Experts put the ingredient up there with daily sunscreen and botox as one of the most effective antiaging tools around.

Retinol is really a form of the powerful antioxidant vitamin A. Once applied, the body metabolizes the vitamin A, converting it into retinoic acid. "Retinoic acid works to boost cell turnover, remove superficial dead skin, flatten the top layers of cells, smoother, more luminous, and even-toned," Tsippora Shainhouse, MD, a board-certified dermatologist in Beverly Hills, California, tells SELF. "It also helps to promote new collagen production, which can help reduce the appearance of fine lines and help thicken skin, making it appear more firm and younger over time." hyperpigmentation.

Yes, retinol can do all that, which is why derms hand out prescriptions Oprah-style to patients with all kinds of skin concerns. While Rx products tend to have more powerful retinoids and more noticeable results, there are plenty of drugstore retinol creams you can buy-without a prescription and usually for less money. But before you buy, you need a little skin-care knowledge to make sure what you're getting is is actually going to work. (You should also consult your derm before trying a new skin-care regimen.) We asked the top dermatology and cosmetic experts to decode the retinol products you might find in the beauty aisle.

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Generally speaking, prescription retinoids are stronger and work faster than over-the-counter options.

Retinoids is a catch-all term for the vitamin A-derived molecules you find in skin-care products.

Retin-A is the purest form of vitamin A, and it's only made in a lab. This prescription-only retinoid is tretinoin (trans-retinoic acid). Because Retin-A is the strongest and most potent version of vitamin A, it can be irritating for some patients, especially when it's not applied as directed. Some of the brand names for Retin-A are Tazorac, Renova, Retin-A Micro, Tretinoin, and Tazarotene.

Over-the-counter retinoid products contain moderately strong retinols or weak retinol esters. Retinol is the natural form of vitamin A, which can be found in the body, while retinol esters are a more stable version of vitamin A that's easier for manufacturers to use and is gentler on the skin.

Prescription Retin-A works more quickly because it's already in retinoic acid form. All other forms of vitamin A need to be converted to retinoic acid before your skin gets the benefits, which means they take a little longer to show results. "Even though many forms of retinoids are in the end broken down into retinoic acid, they are indeed different," says S. Manjula Jegasothy, M.D., CEO and founder of the Miami Skin Institute. "The difference is in their molecular structure and the process they have some time."

Studies of prescription tretinoin products show increased collagen and smoother epidermal cells in four to six weeks. Jegasothy. Over-the-counter retinol and other retinoids usually take longer, though they have not been studied. In addition to being generally weaker than their prescription counterparts and requiring a multistep chemical process in order to work, the OTC products are often combined with other products, such as moisturizing agents, so patients will not see results as quickly as they would with something more potent. "Even though the over-the-counter options often take longer to work, they do not show results when used long-term," says Dr. Shainhouse.

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There's also usually a noticeable difference in price.

Dr. Jegasothy tells SELF that while the price of prescription tretinoin products is always in flux, right now a 30-milliliter tube will probably cost "in the high $200 range." In comparison, OTC retinols can cost as little as $10 and up to $500, depending on the brand, packaging, cosmetic feel, and concentration of active ingredients.

Retinol goes by several names, so you need to scour the ingredients list to find what you want in an over-the-counter product.

You might see retinol appear in an ingredients list as retinyl acetate, the naturally occurring form of retinol; retinyl palmitate and retinaldehyde, two synthetic forms of retinol; and propionic acid, which is a lesser known retinoid, cousin, medically known as vitamin A, propionate.

You can't actually tell from the package how much retinol an over-the-counter product contains.

As it turns out, over-the-counter products are not required. While the FDA regulates prescription-strength retinol, such as Retin-A, it does not regulate cosmeceuticals or over-the-counter topical skin care, says Tahl Humes, MD, cosmetic chemist and medical director of Vitahl Med Spa in Denver and Chicago . And even if they did, most of us would have no idea what. Thus, the OTC brands use our lack of knowledge about retinol to their advantage.

~Since they're not forced to publish their patented retinol type or percentage, they do not and what the concentration means, "says Dr. Jegasothy. "And, if over-the-counter brands do not include the percentage retinol on the packaging, this percentage is simply taken by the retinol molecule."

(It’s worth mentioning, by the way, that while the FDA doesn't regulate OTC ingredients, the agency does, as part of the FDA Cosmetics and Toiletries Act, ensure that products are not harmful.)

Related: 8 Things Your Dermatologist Wants You to Know Before Using Retinol

Over-the-counter products can do great things for your skin—but don't expect to get the same antiaging benefits promised by a prescription.

The derms we talked to agree that if you really want to see antiaging results, the best option is prescription-strength Retin-A, as long as your skin isn't too sensitive. According to Dr. Jegasothy, the best retinol is one dispensed by your trusted board-certified dermatologist that contains at least 0.025 percent retinol or tretinoin. This way you can be sure that you have a clinically studied product which has proven skin penetration and efficacy. If you don't want to go the Rx route, Dr. Humes recommends opting for retinols that are formulated by medical grade cosmeceutical companies—like SkinMedica Retinol Complex 0.5 ($ 78). "They are in the medical practice," he says.

You can assume that anything you're grabbing off the shelf at your local drugstore is lower in concentration than what you'd get from a doctor because the higher-concentration formulas have to be prescribed, and the result, doctors say, is that you're not likely to see great antiaging results. The upside is that you're probably going to wind up with a product that's gentler on your skin. Over-the-counter retinoids are often combined with other ingredients like moisturizers that make the product less drying and less likely to cause redness. This makes them better for the average consumer who may not realize how potent retinol can be. Over time, these products can help even out skin tone and brighten the complexion. “OTC retinols are not as strong, but they will still help keep pores free from debris," says Dr. Jegasothy. "So, while they may not be as antiaging as a prescription, they can still help the skin.” If you're still looking to get those antiaging benefits at a low cost, Dr. Humes recommends Neutrogena Rapid Wrinkle Repair ($ 22), which has been shown to work better than other OTC retinols.

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