The Skincare Guide

Yes! A thin serum won't be able to soak into skin if it's applied over a thick moisturizer. Once you've prepped skin by cleansing and toning, apply your most lightweight formulas first, then lock them in by layering on your heaviest product last.

It depends. For pure moisturization, the same product will do. If your goal is overnight renewal, nighttime formulas usually contain more active ingredients like retinol. And if you'd like to streamline your routine, choose a multitasking day cream that incorporates SPF 30; it'll likely also deliver antioxidants to protect against environmental stressors like pollution.

You don't need to be a specific age to use products considered "antiaging." For example, if you're in your 20s and dealing with dark spots from acne (what derms call "post-inflammatory hyperpigmentation"), brightening formulas can help both fade marks and prevent new ones from appearing. The current "prejuvenation" trend supports skin's collagen and elastin structures with ingredients like peptides and retinol before your first wrinkle. That being said, you can certainly wait till you see the first signs of aging before incorporating these products into your routine.

Retinol is a vitamin A derivative known for speeding up cell turnover. The pro: It's a science-backed ingredient for revealing fresher, firmer skin. The con: It can be potentially irritating. If you've never used it before, start by applying it two or three nights per week and always follow by layering a plain moisturizer on top, which can quell redness and flaking. If your skin is tolerating it well, you can work up to using it every night. Since retinol increases sun sensitivity, remember to use an SPF 30 during the day.

Your everyday moisturizer won't be able to address eye-specific concerns like dark circles and puffiness, which is where eye serums and creams come in. Additionally, eye creams often have balm-like or rich moisturizing properties to support the delicate, thin skin around the eyes.

Two reasons: for radiance and to optimize the performance of skincare products. When we're in our 20s, our skin's life cycle is about a month. Old skin cells naturally shed from the surface of skin. As we age, these old cells become sticky, staying put for longer and longer periods of time instead of shedding. The result? Dullness. And these old cells also inhibit the absorption of treatment ingredients.

That depends on the strength of the exfoliator. Some cleansers and toners feature ingredients that are gentle enough to use twice a day, like fruit enzymes, lactic acid, or low doses of alpha or beta hydroxy acids (see our cleanser and toner sections for recommendations). Or you can use a peel featuring a more potent concentration of acids, generally once or a few times a week; follow the products' instructions, and reduce frequency if you have irritation or redness.

Physical sunscreens are made of natural minerals, either titanium dioxide or zinc oxide, that reflect ultraviolet rays. The plus side: Once you apply them, they work immediately. The downside: They can leave a white cast on skin. Chemical sunscreens like oxybenzone absorb ultraviolet rays. The plus side: These formulas are often more sheer. The downside: It takes 20 minutes after application for them to work. Because every ingredient covers slightly different parts of the ultraviolet spectrum, sunscreens usually contain multiple ingredients for the best broad-spectrum coverage, sometimes combining physical and chemical options.

Yes, you should wear at minimum an SPF 30 daily. Ultraviolet radiation degrades skin's collagen and elastin and is the number one cause of wrinkles and spots. For most of us, cumulative sun damage results from daily activities like driving (UVA rays penetrate glass) and running errands—not beach days. If you skip sun protection, you're handicapping the results you'll get from using hardworking ingredients like peptides and vitamin C. Plus, daily sunscreen use also helps prevent skin cancer.

Yes, often products have a jar icon on their label with a time frame like "12M." That means, once you've opened it, the product is both safe and effective for 12 months. Why? Ingredients can degrade or work less well after being exposed to air and bacteria over time.

Certain ingredients like retinol are unsafe to use during pregnancy, so it's best to check in with your healthcare provider for recommendations.