There's something about a love of skin care that makes even those of us who barely passed chemistry in high school feel like confident cosmetic scientists. You stay up-to-date on the latest breakthrough ingredients, know exactly which acids and actives to recommend to your friends based on their concerns, and can predict which trends will become game-changing skin-care staples. But even the biggest beauty enthusiast can use a refresher every now and then — which is where Allure comes in. Here, in the Allure Ingredient Index, you'll learn how the most important and in-demand ingredients in skin care do what they do best, which ones to use to meet specific goals —clearing up acne, smoothing fine lines, brightening up a dull complexion, and more — how to avoid an unpleasant outcome by keeping incompatible ingredients away from each other, and which ingredients enhance each other's best qualities. And while we can't give you an honorary degree in cosmetic chemistry, we can promise that you'll go into all of your future skin-care shopping expeditions with confidence. In other words: Bookmark this. Allantoin Allantoin, a popular K-beauty ingredient, is a water-soluble compound found naturally in most organisms and often extracted from the comfrey plant — though much of what's found in skin-care products has been synthetically produced in a lab. Its anti-inflammatory, antioxidant, and hydrating qualities make it a common element in products intended to calm sensitive, reactive skin, especially because it also has protective properties. WORKS WELL WITH: jojoba oil, retinol, alpha hydroxy acids MORE INFO: Why K-Beauty Ingredient Allantoin Deserves a Place in Your Sensitive Skin-Care Routine Aloe Vera The extract of the aloe vera plant, a type of succulent, is found in countless skin-care products because it seems to have countless benefits. In addition to providing hydration and antioxidant defense against skin-damaging free radicals, it's best known for its soothing and healing qualities, especially for sunburns. The plant's cooling effects reduce redness and inflammation, and that calming power — combined with its antibacterial nature — can even help prevent blackhead and whitehead flare-ups. WORKS WELL WITH: retinol, glycerin MORE INFO: How Does Aloe Vera Help Skin and Hair? SHOP: The 11 Best Aloe Skin-Care Products for Soothing Skin Alpha Hydroxy Acid Alpha hydroxy acids (AHAs) are a family of water-soluble acids, including lactic, malic, tartaric, and the most commonly used acid in skin care: glycolic. They are typically used to chemically exfoliate the outer layer of skin, which leads to a brighter, more even-toned complexion. Although regularly recommended by dermatologists, AHAs do increase photosensitivity, so using sunscreen every day is even more important than usual — even if you're applying these acids at night. WORKS WELL WITH: salicylic acid, glycerin DOESN'T PAIR WELL WITH: vitamin C, retinol, hydroquinone MORE INFO: Your Guide to Alpha Hydroxy Acids and How They Work Argan Oil Argan oil, derived from kernels of the Moroccan argan tree fruit, has become a popular natural ingredient because it's a noncomedogenic source of moisture, vitamins, omega-3 fatty acids, and antioxidants. In addition to its own properties, argan oil acts as a vehicle for other beneficial ingredients, such as ceramides, to help improve the skin barrier. It can also help fat-soluble ingredients like vitamins A and E be more effectively absorbed into the skin and retinols be better tolerated. WORKS WELL WITH: ceramides, retinol, vitamin E MORE INFO: The Many Ways Argan Oil Benefits Skin and Hair Azelaic Acid Azelaic acid, a member of the dicarboxylic acid family, occurs naturally in grains such as barley, rye, and wheat. It is antibacterial, keratolytic, and comedolytic, which makes it an effective acne-fighting ingredient. In addition to killing p. Acnes bacteria, this antioxidant reduces inflammation and loosens skin cells so they won't clog pores. Bonus: It can help even out skin tone too. WORKS WELL WITH: benzoyl peroxide, tea tree oil, niacinamide MORE INFO: Azelaic Acid Is Reddit's Secret Ingredient to Fighting Acne Bakuchiol Often touted as a gentler botanical alternative to retinol, bakuchiol is an antioxidant derived from the seeds of the babchi plant. It's a popular ingredient in natural medicine for soothing rashes and calming redness. In skin care, thanks to its ability to boost cell turnover without the harshness for which retinoids have a reputation, it has become an increasingly popular option for those looking to diminish wrinkles, skin laxity, and sun damage. WORKS WELL WITH: retinol, ceramides, squalane MORE INFO: What Is Bakuchiol? Experts Explain the Benefits of the Natural Alternative to Retinol SHOP: Bakuchiol Skin-Care Products for Those Seeking a Natural Retinol Alternative Benzoyl Peroxide Benzoyl peroxide is one of the most trusted ingredients for treating acne. It fights pimples in three ways: by releasing oxygen onto the skin to destroy bacteria (it's antimicrobial), by exfoliating (dead skin cells can clog pores), and by reducing inflammation. Benzoyl peroxide is believed to be especially effective against red, inflamed bumps and cystic acne. (But please note, it's also quite effective at discoloring any fabric that it touches.) WORKS WELL WITH: salicylic acid, ceramides, hyaluronic acid DOESN'T PAIR WELL WITH: retinol, vitamin C, hydroquinone MORE INFO: The Complete Guide to Benzoyl Peroxide and Its Acne-Fighting Powers Beta Hydroxy Acid Unlike alpha hydroxy acids, which are water-soluble, beta hydroxy acids are oil-soluble, enabling them to penetrate skin more deeply. They are ideal for getting into pores to clear acne-causing clogs, while also encouraging exfoliation. There are several types of beta hydroxy acids, but they're usually found in skin-care products as salicylic acid. WORKS WELL WITH: alpha hydroxy acids, tea tree oil, charcoal DOESN'T PAIR WELL WITH: retinol MORE INFO: Here's Exactly What Salicylic Acid Does to Your Skin Caffeine Obviously, caffeine is one of the most popular ingredients to consume from a cup, but it is also found in a wide variety of skin products like eye creams and body lotions. Created synthetically in the lab or naturally derived from a variety of plants, caffeine is believed to temporarily reduce redness and puffiness by constricting blood vessels. WORKS WELL WITH: hyaluronic acid, aloe, peptides SHOP: Why Caffeine Belongs in Your Skin Care Just as Much as Your Coffee Cannabidiol Short for cannabidiol, CBD is one of over 80 compounds called cannabinoids that can be extracted from the cannabis sativa plant. Unlike its fellow compound THC, it won't get you high; it can, however, have an anti-inflammatory effect when used in skin care. This has led to the inclusion of CBD in acne-fighting and pain-reducing products, though more research is needed to confirm just how effective it is in clearing skin and alleviating aches. WORKS WELL WITH: squalane, vitamin E, hyaluronic acid MORE INFO: Everything You Need to Know About CBD Oil in Beauty Products SHOP: 21 CBD Products That Will Elevate Your Beauty Routine But Won't Get You High Ceramides Ceramides exist naturally in your skin, providing an essential part of its barrier. These lipids help protect skin from environmental agitators like pollution and lock in hydration. As we age, however, they become depleted, increasing possible dryness and irritation. Fortunately, by using products that contain ceramides, whether a moisturizer or a serum, you can replenish this important contributor to skin's smoothness, comfort, and softness. WORKS WELL WITH: glycerin, retinol, peptides MORE INFO: What Are Ceramides, and Why Are They Important in Your Skin-Care Routine? SHOP: 15 Best Ceramide-Spiked Skin-Care Products to Nourish Dry, Irritated Skin Cica Cica goes by many names — Centella asiatica, gotu kola, Indian pennywort, tiger grass — but its purpose in skin care is singular: to calm irritated, red skin. Research has shown cica has the potential to help healing with soothing properties that are due to its composition of amino and fatty acids, beta-carotene, and vitamins. In addition, some dermatologists believe it may have an impact on signs of aging, such as lines and discoloration, because of its ability to boost circulation, decrease moisture loss, and help with cellular repair. WORKS WELL WITH: alpha hydroxy acids, glycerin, hyaluronic acid MORE INFO: Why Cica Is the Latest K-Beauty Ingredient Taking Over Skin-Care Products SHOP: The 11 Best Cica Skin-Care Products to Soothe Redness and Irritation Charcoal Charcoal's adsorptive properties make it an appealing skin-care ingredient, particularly in products aimed at clearing pores and reducing excess oil. When dirt and grease come in contact with the carbon that makes up charcoal, they stick to it, then get washed away upon rinsing. This has made charcoal a popular ingredient in cleansers and masks, especially those used for acne-prone skin. WORKS WELL WITH: salicylic acid, glycolic acid, jojoba oil MORE INFO: How Charcoal Clears Up Oily and Acne-Prone Complexions SHOP: 13 Best Activated Charcoal Products to Clear Congested Pores Coconut Oil Coconut oil is one of the most popular natural moisturizers in all of skin care, thanks to how well it addresses dryness. Its fatty acids have antimicrobial effects that can help fight bacterial, viral, and fungal pathogens, plus its ability to break down lipid-soluble substances makes it a great makeup remover. That said, it is comedogenic, so it's not recommended in leave-on face products for oily, acne-prone skin. WORKS WELL WITH: glycerin, hyaluronic acid MORE INFO: The Best Ways to Use Coconut Oil in Your Beauty Routine Colloidal Oatmeal Made by grinding oat grain, Avena sativa, into a fine powder and boiling it, colloidal oatmeal is one of the most reliable soothers found in skin care. For centuries, oatmeal has been used topically to relieve itchiness and skin irritation. Studies have shown that it can help strengthen the skin barrier and inhibit the release of cytokines that produce inflammation. It's often recommended for people with conditions like dry skin and atopic dermatitis; but because of its emollient qualities, colloidal oatmeal is beneficial to anyone seeking softer, more comfortable, moisturized skin. WORKS WELL WITH: ceramides, hyaluronic acid MORE INFO: Why Colloidal Oatmeal Should Be Part of Your Skin-Care Regimen Ginseng Ginseng has been a nutritional superstar for years, especially in traditional Asian medicine. Extracts from the antioxidant-rich plant may calm redness, can protect against UV-induced skin damage, and may reduce the appearance of fine lines. WORKS WELL WITH: niacinamide, bakuchiol, glycolic acid MORE INFO: Why You're Seeing Ginseng in So Many Korean Skin-Care Products Right Now Glycerin Glycerin is a colorless, odorless, plant-derived humectant. When applied topically, humectants can attract water from deeper skin layers and from the environment around you. (Finally, a reason to appreciate humidity!) Glycerin also helps slow the evaporation of water from your skin, which is why it's frequently found in moisturizers and serums, as well as in cleansers which can dry out the skin as they get their job done. WORKS WELL WITH: niacinamide, alpha hydroxy acids, allantoin MORE INFO: Why Glycerin Is the Ultimate Moisturizing Ingredient in Skin-Care Products SHOP: The 14 Best Glycerin Skin-Care Products for Immediate Hydration Glycolic Acid Glycolic acid, one of several water-soluble alpha hydroxy acids used in skin care, is arguably the most popular because it has the smallest molecular size, thus being the most efficient at penetrating skin. A chemical exfoliant derived from sugar cane, glycolic acid is used to improve skin texture and tone by sloughing away dead surface cells to reveal a brighter complexion with less discoloration. It can even help prevent breakouts by removing the buildup that contributes to clogged pores. Because glycolic acid causes photosensitivity, dermatologists often recommend using it at night — and following up with sunscreen in the morning is a must. WORKS WELL WITH: salicylic acid, glycerin DOESN'T PAIR WELL WITH: retinol, vitamin C MORE INFO: How Glycolic Acid Gets Skin Glowing Stat SHOP: The 16 Best Glycolic Acid Treatments for Brighter Skin Grapeseed Oil Friendly to all skin types and effective in addressing a number of concerns, grapeseed oil is one of the most prolific natural ingredients found in skin care. It's best known for its antioxidant power — it contains polyphenols and vitamins A, C, and E — but its linoleic acid can also moisturize dehydrated skin, even out skin tone, reduce the appearance of lines, and diminish redness, all without clogging pores. WORKS WELL WITH: squalane, glycerin MORE INFO: Why Grapeseed Oil Is in So Many Skin-Care Products Hyaluronic Acid Hyaluronic acid is a sugar molecule that occurs naturally in the skin and binds to water. This lightweight humectant draws in hydration to plump up your skin and give it a glow, which is why it's featured in so many skin-care products. Safe and beneficial for virutally anyone of any age to use, this ingredient is especially helpful for mature skin that has stopped making as much hyaluronic acid as it once naturally did. (Like ceramides, hyaluronic acid also exists naturally in the skin.) In addition to its topical uses, hyaluronic acid is the main ingredient in most injectable dermal fillers for plumping lines and lips. WORKS WELL WITH: vitamin C, glycerin, squalane MORE INFO: What Is Hyaluronic Acid, and Why Is It in So Many Skin-Care Products? SHOP: The Best Hyaluronic Acid Serums, According to Dermatologists Hydroquinone Hydroquinone decreases the production of melanin by inhibiting the enzyme tyrosinase. Because of this, people often refer to it as a "skin-bleaching ingredient"; however, dermatologists who recommend it see it as a means of reducing stubborn hyperpigmentation, like melasma. It is not recommended for long-term use, or for those who are pregnant or breastfeeding. Hydroquinone is banned in Europe, but the FDA still deems it safe for topical application (the European ban was based on studies of orally administered hydroquinone). To ensure the safest approach possible, always talk to your dermatologist before using a product that contains this ingredient. WORKS WELL WITH: retinol, kojic acid DOESN'T PAIR WELL WITH: benzoyl peroxide MORE INFO: The Dos and Don'ts of Incorporating Hydroquinone Into Your Skin-Care Routine Jojoba Oil Although it's called jojoba oil, this ubiquitous natural ingredient is technically a wax, and its wax esters happen to be very similar to the major constituents of human sebum. This quality makes it an excellent moisturizer for all skin types, including acne-prone and sensitive. Lightweight and noncomedogenic, jojoba oil has documented anti-inflammatory, antioxidant, and antimicrobial properties. Its dual humectant and emollient qualities mean it both draws in moisture and helps soften skin. WORKS WELL WITH: salicylic acid, retinol MORE INFO: Can Jojoba Oil Help Clear Up Acne? Kojic Acid Derived from several types of mold including mushrooms, kojic acid is a byproduct of fermentation. Instead of exfoliating, kojic acid does its discoloration-diminishing work by inhibiting the formation of the enzyme tyrosinase, which is needed to produce melanin. Typically, it is better tolerated than often irritating AHAs and BHAs, but kojic acid is still prone to causing some redness and reactivity, so it's best to use this hyperpigmentation reducer with soothing ingredients and not for long periods of time. WORKS WELL WITH: hydroquinone, tranexamic acid, niacinamide DOESN'T PAIR WELL WITH: alpha hydroxy acid, beta hydroxy acid MORE INFO: How Kojic Acid Annihilates Hyperpigmentation Lactic Acid Lactic acid is one of the gentlest alpha hydroxy acids in the family, not to mention one of the smallest molecularly. Like other AHAs, this water-soluble exfoliating ingredient breaks down the proteins that bind skin cells together, therefore increasing cell turnover. The result is smoother, more even-toned, brighter skin with less acne-enabling pore congestion. But it sets itself apart from other acids with its natural moisturizing factor. (Heads up, vegans: Though lactic acid occurs in dairy, typically it is synthetically produced when found in skin care.) WORKS WELL WITH: salicylic acid, glycerin, hyaluronic acid DOESN'T PAIR WELL WITH: retinol MORE INFO: Lactic Acid Smooths Skin With the Same Components as Sour Milk Niacinamide Niacinamide, a form of vitamin B3, has a long list of benefits: It works with the skin's natural chemistry to rebuild the lipid layer; strengthens the skin's barrier; minimizes the appearance of pores; improves texture; and prevents UV damage and inflammation (with its antioxidant properties). Furthermore, some evidence has shown that niacinamide reduces acne by preventing bacteria growth. It can be found in countless formulas, but because it's water-soluble, it's especially effective in serums. WORKS WELL WITH: retinol, peptides, salicylic acid DOESN'T PAIR WELL WITH: vitamin C MORE INFO: Why Niacinamide Is One of the Most In-Demand Ingredients in Skin Care Right Now SHOP: The Best Niacinamide Products for Clear, Bright, Calm, Shine-Free Skin Peptides Peptides are amino acid chains that can penetrate the skin and essentially serve as messengers to skin cells. Categorized as either signal, carrier, enzyme-inhibitor, or neurotransmitter-inhibitor, each type of peptide works in the skin in a specific way, resulting in more collagen and elastin production — the key to firmness. Peptides are compatible with numerous other ingredients, but do their best work in leave-on products like creams and serums. WORKS WELL WITH: squalane, lactic acid, hyaluronic acid, retinol MORE INFO: Peptides: How This Ingredient Helps Build Collagen for Firmer Skin SHOP: The 15 Best Peptide Skin-Care Products for Smoother and Plumper Skin Polyhydroxy Acids Polyhydroxy acids — the most common being gluconolactone, galactose, and lactobionic acid — are essentially second-generation alpha hydroxy acids. They too are water-soluble and exfoliate surface skin cells to promote a brighter, smoother complexion. However, their larger molecular size means more superficial penetration — and less possibility of irritation and photosensitivity. They also have the ability to fight glycation, which occurs when digested sugar attaches to and potentially weakens the collagen in your skin. WORKS WELL WITH: alpha hydroxy acids, beta hydroxy acids, glycerin MORE INFO: Your Guide to PHAs and Why They're Trending in Skin Care Right Now Retinol Retinol, one of several types of retinoids, is among the most popular forms of vitamin A found in skin care for good reason: Myriad studies have found that retinol helps soften fine lines, improve texture, diminish discoloration, and unclog pores to help prevent breakouts by increasing skin-cell turnover. Sunlight can reduce its efficacy, so retinol is best used at night, and with consistency — it takes about 12 weeks for skin to show results. But retinol has been known to cause irritation, so for new users, that consistency could start as infrequently as once a week. WORKS WELL WITH: peptides, glycerin, ceramides DOESN'T PAIR WELL WITH: alpha hydroxy acids, vitamin C, benzoyl peroxide MORE INFO: Retinol: Everything You Need to Know About the Buzziest Skin-Care Ingredient SHOP: 21 Best Retinol Creams and Serums You Can Buy Without a Prescription Salicylic Acid Salicylic acid is the most common beta hydroxy acid found in skin-care products, primarily in formulas intended to prevent and clear acne. Because it's oil-soluble, salicylic acid can penetrate pores deeply to unclog them, dissolving the congesting debris via exfoliation. It also acts as an anti-inflammatory that expedites the healing of reddened whiteheads, blackheads, and pustules. You'll find salicylic acid in a wide variety of formulas, including cleansers, moisturizers, serums, and spot treatments. WORKS WELL WITH: alpha hydroxy acids, tea tree oil, charcoal, benzoyl peroxide DOESN'T PAIR WELL WITH: retinol MORE INFO: Here's Exactly What Salicylic Acid Does to Your Skin SHOP: The 17 Best Salicylic Acid Products to Banish Breakouts and Improve Skin Clarity Snow Mushroom Does it sound like something a fairy might live in? Yes, but snow mushroom — also known as Tremella fuciformis and silver ear mushroom — has humectant properties, pulling water into the skin for a boost of hydration. Furthermore, its fatty acids potentially help hold onto that moisture. Antioxidant and anti-inflammatory snow mushroom also contains vitamin A and kojic acid, giving it the potential to even out skin tone (though more research is needed to show just how effective it is on that front). WORKS WELL WITH: alpha hydroxy acids, hyaluronic acid, squalane MORE INFO: The Benefits of Adding Snow Mushroom to Your Skin-Care Routine Squalane Not to be confused with squalene, which is naturally produced by the skin's sebaceous glands, squalane is an emollient (skin-smoothing) ingredient commonly derived from plants such as olives and rice bran. Squalane is an effective way to seal in moisture in any skin type, and is especially helpful for addressing issues where the skin barrier is disrupted and transepidermal water loss is an issue, including eczema, acne, and psoriasis. It is found in numerous types of products, but squalane is particularly effective as an ingredient in moisturizers like creams and lotions. WORKS WELL WITH: hyaluronic acid, peptides, retinol MORE INFO: The Subtle Yet Significant Difference Between Squalane and Squalene in Skin Care Sulfur Sulfur naturally occurs practically everywhere — in our bodies, in rocks, etc. While it has a reputation for being kind of stinky, its skin-care benefits are anything but. This anti-inflammatory, antibacterial element is a favorite ingredient in pimple and spot treatments because it absorbs acne-triggering excess oil by drying out the skin's surface and gently exfoliating to unclog pores. Strength differs from product to product, but dermatologists say using sulfur in concentrations up to 10 percent for up to eight weeks is safe and effective when trying to clear breakouts. WORKS WELL WITH: niacinamide, glycolic acid, glycerin DOESN'T PAIR WELL WITH: retinol, benzoyl peroxide MORE INFO: Why Sulfur Is Skin Care's Ultimate Exfoliator and Healer Tea Tree Oil Tea tree oil, derived from the leaves of the Melaleuca alternifolia tree, has been used as an antiseptic for ages. Often used to help reduce acne and related irritation, tea tree oil has also been shown to be somewhat effective in treating nail fungus, athlete's foot, and dandruff. However, because it's an essential oil, it comes with its own potential for irritation, so it's often paired with gentler carrier oils like grapeseed and jojoba. WORKS WELL WITH: jojoba oil, grapeseed oil, coconut oil DOESN'T PAIR WELL WITH: retinol, benzoyl peroxide MORE INFO: Why Tea Tree Oil Is Still Beloved by Dermatologists Tranexamic Acid Tranexamic acid, a synthetic derivative of the amino acid lysine, has been used in medicine to treat excessive blood loss due to its blood-clotting properties. However, in topical skin care, it has been shown to reduce discoloration by inhibiting UV-induced melanin synthesis. Although several other popular skin-care acids diminish hyperpigmentation, tranexamic acid does so with less irritation and has the ability to work well with other tone-evening ingredients. WORKS WELL WITH: retinol, kojic acid, vitamin C MORE INFO: Why Tranexamic Acid Is the New Secret to Fading Dark Spots Turmeric Turmeric is a long-loved botanical ingredient that has been popular in Asian recipes for centuries, but its benefits go far beyond flavor and nutrition. Research has shown that curcumin, a chemical compound found in turmeric, has the potential to decrease UV damage and clear up acne when applied to skin. This antioxidant and antibacterial spice is often the star of products intended to soothe. And because turmeric plays well with other ingredients, it can fill a supporting role in numerous types of skin-care formulas. Just be careful — its yellow hue can sometimes stain skin, so you might want to look for it primarily in rinse-off cleansers, exfoliators, and masks. WORKS WELL WITH: vitamin C MORE INFO: Turmeric Is the Calming and Brightening Natural Ingredient Your Skin-Care Routine Needs SHOP: The Best Skin-Care Products With Turmeric to Soothe and Brighten Vitamin C Vitamin C is an antioxidant that protects skin from UV and free-radical damage, smoothing fine lines and fading hyperpigmentation in the process. Studies show it inhibits the enzyme in charge of discoloration to decrease existing dark spots, and it brightens skin and activates collagen production, which makes skin plumper and firmer. In the morning, use vitamin C in a serum or moisturizer under sunscreen. Studies show vitamin C can protect skin from UV exposure in ways that sunscreen does not — layering them together gives you the ultimate coverage. WORKS WELL WITH: hyaluronic acid, vitamin E DOESN'T PAIR WELL WITH: retinol, alpha hydroxy acids, benzoyl peroxide MORE INFO: Why Vitamin C Is One of the Most Effective Skin-Care Ingredients SHOP: The Best Vitamin C Serums, Moisturizers, and More to Brighter Skin Vitamin E Typically listed in skin-care ingredients as tocopherol or tocopheryl acetate, vitamin E is an oil-soluble antioxidant that fights the damaging effects of free radicals. Additionally, vitamin E has moisturizing, hydrating, and healing benefits, helps strengthen the skin barrier, and can even be soothing thanks to its anti-inflammatory properties. It's not ideal for acne-prone or sensitive skin, but if you're dead-set on trying vitamin E, use an oil or cream as its vehicle — the dose used in serums can be a little too potent for reactive skin types. WORKS WELL WITH: vitamin C, jojoba oil MORE INFO: A Beginner's Guide to Vitamin E and What It Does for Your Skin SHOP: The 13 Best Vitamin E Products to Moisturize and Protect Your Skin Witch Hazel Witch hazel, essentially the original toner, has been used for centuries to soothe and clean skin. This anti-inflammatory, antioxidant botanical extract is commonly used to reduce excess oil, making it a favorite among those with acne-prone skin; however, it can be drying if overused, so you may want to avoid it if you have very dry skin. In addition to breakout control, witch hazel is also used to prevent razor burn, treat ingrown hairs, soothe redness, and minimize the obviousness of pores. WORKS WELL WITH: aloe, salicylic acid, alpha hydroxy acids MORE INFO: How to Use Witch Hazel on Acne-Prone Skin, According to Dermatologists
