Your A-Z Skin-Care Glossary: Here Are the Skin-Care Terms You Actually Need to Know

So, you wanna build a skin-care routine? Well, that probably seemed like a great idea about 800 Google searches ago—and then you realized that learning about skin care is a little more like learning a whole new language (or going back to Bio 101) and a little less chill pampering than you’d hoped.

That’s what we’re here for. In addition to our comprehensive skin-care guide, we built this cheat sheet of skin-care terms that will help you parse everything from your favorite blogger’s haul posts to the back of your sunscreen bottle. We've sorted the terms in alphabetical order. If there's anything you think we've left out, reach out to us at askabeautyeditor@self.com to let us know, and we'll do our best to update this post as it makes sense.

Happy skin-caring!

Acne: The root of all acne is a pore clogged with dirt, dead skin cells, and sebum. Beyond that, there are many ways acne may manifest, such as whiteheads (also called closed comedones), blackheads (also called open comedones), and cystic acne (occurring deeper in the skin). If the acne is inflamed—red, painful, swollen—that’s a sign that bacteria are also involved.

Active ingredient: In general, an active ingredient is the ingredient in a skin-care product that’s doing the thing you want the product to do. In an acne cleanser, the active ingredient may be something like benzoyl peroxide or salicylic acid. But, depending on the way the claims are worded on the packaging, the ingredient may or may not be called out in a drug facts box and the product may or may not be considered a drug rather than a cosmetic.

Alpha hydroxy acids (AHAs): A type of chemical exfoliant (see below), AHAs loosen the bonds that hold skin cells together, which allows them to be easily swept away, revealing new skin cells underneath. Glycolic acid and lactic acid are two popular types of AHAs.

Antioxidant: Ingredients that can help neutralize free radicals (highly reactive molecules in the environment). When the balance of free radicals and antioxidants in the skin is out of whack, free radicals can cause damage, possibly resulting in premature aging of the skin.

Ascorbic acid: See “Vitamin C.”

Azelaic acid: A type of acid synthesized by yeast, barley, and wheat that’s believed to have a gentle exfoliating effect. Research has shown that it’s effective at managing both acne and acne-like bumps that are a common symptom of rosacea. Azelaic acid comes in prescription and over-the-counter forms.

Beta hydroxy acids (BHAs): A type of chemical exfoliant (see below), BHAs loosen the bind that hold skin cells together, allowing them to be easily swept away, revealing new skin cells underneath. Salicylic acid is a well-known type of BHA.

Benzoyl peroxide: An active ingredient against acne, benzoyl peroxide can kill the type of bacteria that’s often responsible for inflamed acne. Benzoyl peroxide can also irritate or dry out skin, so it’s important to also use a moisturizer when you’re using it.

Broad spectrum: A label applied to sunscreens that offer protection against both UVA and UVB rays, both of which contribute to your risk for skin cancer.

Chemical exfoliant: Chemical exfoliants are the gentler cousins of physical exfoliants. Where physical exfoliants manually scrub or brush off dead skin cells, chemical exfoliants (ingredients like lactic acid, glycolic acid, and salicylic acid) break the bonds between those dead skin cells so that they are easily washed away.

Collagen: A protein found in many parts of the body, including your bones, muscles, and ligaments. In skin, it’s important for keeping the face looking firm and plump. But collagen production in our bodies slows down as we age, and exposure to UV radiation degrades collagen as well. That’s why collagen—and products that claim to boost the production of collagen—have become such popular skin-care ingredients in recent years. However, collagen is too big of a molecule to make it through to the deeper layers of the skin when applied topically. And eating or drinking collagen supplements hasn’t been proven to help much. The most helpful thing you can do for your collagen is to wear sunscreen to prevent the loss of what you already have.

Comedones: Clogged pores. They may be open (blackheads) or closed (whiteheads). For more, see “Acne.”

Contact dermatitis: A condition that causes stinging, redness, burning, flaking, or scaling after coming into contact with something, often a makeup or skin-care product. The reaction can be related to either an irritant or an allergy.

Detox: The concept of removing toxins from your body. Some skin-care products claim they can “detox” you, but that’s not really how it works. In reality, detox products generally just remove dead skin cells and excess oil.

Double cleansing: A technique that involves using two cleansers—an oil-based cleanser first followed by a typical foaming or water-based cleanser—to more effectively remove heavy makeup, sunscreen, or oil.

Eczema: A skin condition that causes itchy, bumpy rashes in infants and children. In adults, eczema can also lead to patches of thickened and very dry skin. The term atopic dermatitis is often used interchangeably with eczema, but atopic dermatitis is actually just one form of eczema.

Emollient: Moisturizing ingredients that can penetrate into the spaces between skin cells, which leaves the skin feeling softer and smoother. Face oils—such as squalane oil, argan oil, and jojoba oil—generally act as emollients and/or occlusives.

Free radicals: Molecules that have gained or lost an extra electron, which means they need to “steal” electrons from surrounding sources. Free radicals are sometimes created in the body in small amounts through totally normal and natural processes. But they can also be created by exposure to some kinds of radiation, including UV rays. And in high enough doses, free radicals can damage the skin. Antioxidants are thought to neutralize free radicals and prevent that damage.

Fragrance-free: Fragrances are another common irritant to those with sensitive skin, which is why it may be helpful to look for products that are fragrance-free, which means no scents have been added to the product. But beware of those labeled “unscented,” which may indicate that a scent has been added just to cover up the natural scent of the product.

Glycolic acid: A type of alpha hydroxy acid (AHA; see above) derived from sugar cane. Glycolic acid is a commonly used chemical exfoliant (see above).

Humectant: A type of hydrating ingredient found in moisturizers that actually draws water into the skin, but doesn’t necessarily keep it there. Common ingredients like glycerin and hyaluronic acid are humectants.

Hyaluronic acid: Hyaluronic acid is found naturally in the skin and acts as a humectant, meaning it can draw moisture into the skin; products with these molecules allow moisture to bind to the skin without feeling greasy or heavy.

Lactic acid: A type of alpha hydroxy acid (AHA; see above) derived from milk, fruit, or vegetable sources. Lactic acid is a commonly used chemical exfoliant (see above).

Lipids: Organic compounds (meaning they contain carbon) found all over your body. They occur both on the top of your skin (as sebum) and within the stratum corneum (as ceramides, cholesterol, and fatty acids).

Keratosis pilaris: Sometimes referred to as “chicken skin,” keratosis pilaris looks like tiny, often red, white, or flesh-colored bumps on the skin. It’s totally harmless and caused by a buildup of keratin around the hair follicle, which can clog pores and cause inflammation or redness in the area.

Melanin: The pigment that gives skin its color, created by cells called melanocytes.

Melasma: A skin condition that causes grayish or brown patches of skin, primarily on the face. It’s often triggered by hormonal changes, including pregnancy, which is why melasma is sometimes called the “mask of pregnancy.”

Micellar water: Used as a cleanser, micellar water is made up of micelles (spherical clusters of surfactants) and water. Rather than washing it off like a typical cleanser, micellar water is usually wiped on with a cotton round, which also wipes off dirt and excess oil, and then left to dry before continuing with the rest of your skin-care routine.

Niacinamide: This is a form of vitamin B3 (niacin) that can be applied to the skin. There is some research to suggest that niacinamide: can be helpful for managing acne, rosacea, and signs of aging including hyperpigmentation, fine lines, and wrinkles.

Non-comedogenic: A skin-care ingredient that’s comedogenic means that it can clog pores. So, if you have acne-prone skin, it’s important to seek out products that are non-comedogenic.

Occlusive: Another type of ingredient often found in moisturizers that doesn’t add hydration, but rather seals the skin so that as little hydration as possible is lost through the stratum corneum. Occlusives like petrolatum and silicones are a mainstay of treatment for eczema and other dry skin issues.

Parabens: A type of preservative in skin-care products that can be irritating, especially for people who already have sensitive skin or a skin condition like eczema or psoriasis. For more about parabens, check out our post on what the science says about 10 controversial cosmetics ingredients here.

Peptides: Chains of amino acids that make up part of a protein. In skin care, peptides are used because they’re thought to penetrate more deeply into the skin than large, full proteins, like collagen.

Psoriasis: A skin condition in which the normal life cycle of skin cells is sped up, which most commonly results in a thick, scaly buildup of so-called “plaques” on the surface of the skin. Other types of psoriasis cause different types of rashes and may also affect the nails or joints.

Phthalates: Phthalates are primarily used as plasticizers to keep plastic from becoming brittle and breaking, and are also used in some of the fragrances in products like lotions and shampoos. There are lots of different types of phthalates, and we’re exposed to them a lot. For more on phthalates, read our post on what the science says about 10 controversial cosmetics ingredients here.

Retinoids: These compounds—retinol, retinal (or retinaldehyde), retinoic acid, and synthetic retinoids like Adapalene and Tazerac—are one of only two proven ways to prevent the signs of aging. (The other is sunscreen!) Retinoids, which are forms of vitamin A, work by stimulating the skin cell-shedding process from below, leading to smoother skin and a reduction in both signs of aging and acne. These come in both prescription and over-the-counter products, so if you aren’t satisfied with the results of an over-the-counter option, check with a dermatologist about getting a prescription version. Retinoids are also notorious for causing irritation when you first start using them, so it’s crucial to apply them just a few days a week to start with and to apply a moisturizer right after using them.

Rosacea: A common skin condition that causes excess facial redness, typically in the form of flushing, small red raised bumps, or broken blood vessels. It can be triggered by everything from the weather to exercise to skin-care ingredients to food.

Salicylic acid: A type of beta hydroxy acid (BHA; see above) derived from willow bark. Salicylic acid is oil soluble, which allows it to penetrate deeper into your oily pores. It’s a popular type of chemical exfoliant (see above) in products that treat acne.

Sebum: The oil on the top of your skin composed of lipids, particularly wax esters, triglycerides, and squalene. Some people naturally produce more sebum than others, giving them oilier skin. Sebum can also contribute to the development of acne.

Sensitive skin: Unfortunately, sensitive skin isn’t exactly a clinical term, so it can be a bit subjective. But, generally, if you find your skin is easily irritated—possibly due to a skin condition, like eczema, psoriasis, or rosacea—or if you have known allergies to skin-care products, you can be considered to have sensitive skin.

SPF: A measure of the amount of added protection a particular product provides against the sun’s rays. It’s important to note, however, that SPF is not an indication of the time it will take you to burn (SPF 50 needs to be applied just as frequently as SPF 30, for instance), and the SPF value of a sunscreen only takes into account its UVB protection.

Squalane: Squalane is a light moisturizing oil that mimics a component of sebum, the oily substance our skin produces. There is limited research on the effect of topical squalane on skin, but in general it acts like an emollient when applied to the skin, which means that it can squeeze into the spaces between skin cells and make your face feel smoother and more moisturized without being too heavy or occlusive.

Stratum corneum: The outermost layer of your skin. It’s composed of skin cells held together by intercellular lipids with a layer of dead skin cells and oil on top. It keeps hydration in and potential irritants and allergens out.

Sulfates: Ingredients commonly found in cleansers and shampoos that help the product lather and remove dirt and oil. But they can also be too harsh for some people and end up stripping the skin and hair of too many of its natural oils, resulting in dry or irritated skin. If you have sensitive skin, you may want to be avoid sulfate-containing products or at least use them minimally. For more on sulfates, read our post on what the science says about 10 controversial cosmetics ingredients here.

Toner: A type of skin-care product originally designed to help balance the skin’s pH. Today, toners are generally used to deliver active ingredients like chemical exfoliators or antioxidants.

Vitamin C: This vitamin is essential for producing collagen and other important compounds in the body. And, when it’s applied topically, it can function as an antioxidant thus preventing UV-related damage. It can also inhibit the production of melanin (pigment) in the skin, making it a good option for lightening dark spots due to photoaging or other kinds of damage. But beware that all forms of vitamin C are not created equally—some are more or less effective or stable than others. Vitamin C often appears on the ingredients label as these derivatives—look for ingredients like magnesium ascorbyl phosphate, ascorbyl 6-palmitate, ascorbic acid sulfate, or L-ascorbic acid (also referred to simply as ascorbic acid).

Originally Appeared on Self