According to Google, These Are 2021's Top Trending Skincare Questions

End the year with the intel—and products—everyone’s looking for.
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Google just released its behind-the-scenes intel on the top trending searches of 2021, including the most-searched skincare questions of the year—and the findings are as illuminating as a Skinceuticals serum. According to the traffic masters, trending queries are the searches that had a high spike in traffic over a sustained period in 2021, so you know everyone and their mother was intrigued. This year, people wanted to get the down-low on everything from what niacinamide actually does to what the heck slugging is and which ingredients are worth avoiding (smart moves, especially in light of the ever-emerging news on carcinogenic benzene).

For some insight and all-important answers, keep reading.  

What skincare products do not mix?

Retinol is the gold standard for anti-aging, but as one of the most sensitizing ingredients, you want to be careful. Ava Shamban, MD, a Beverly Hills dermatologist, cautions against mixing retinol with alpha hydroxy acid exfoliants and beta hydroxy acids like salicylic acid, since the combination will over-exfoliate skin. Drying toners, astringents, and cleansers will also dry out skin when used with retinol, and benzoyl peroxide will make the retinol less effective. Outside of retinol, avoid simultaneously using niacinamide and vitamin C; when mixed, the resulting niacin can cause redness. Try Avène RetrinAL 0.1 Intensive Cream for retinol without any downsides. 

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Credit: Avene

What does niacinamide do?

Niacinamide does a world of things, chiefly helping to tighten pores, fight signs of aging, lighten dark spots, and control acne. New York dermatologist Debra Jaliman, MD, previously told Health that the potent antioxidant can whisk away dullness, and dermatologist William Kwan, MD, adds that it can moisturize skin by decreasing water loss. Versed Just Breathe Clarifying Serum uses the ingredient to banish acne and help shoppers' skin feel "younger and fresher" within 24 hours. 

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Credit: Versed

What is slugging in skincare?

Surprisingly, slugging in skincare doesn't involve snail mucus (which is good in its own right, though). Instead, slugging is the Reddit-sourced practice of coating your face with petroleum jelly or a similar ointment to form a seal on your skin, which prevents water loss, keeps skin plump, and helps a damaged skin barrier repair itself. You can use Vaseline's Petroleum Jelly or CeraVe's Healing Ointment, or The Honest Company's Organic All-Purpose Balm for an eco-friendly option. Is it actually beneficial? Dermatologists say yes, especially if you have dry or sensitive skin.

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Credit: Amazon

What order to put on skincare?

To get the most bang for your skincare buck, apply products with the thinnest, most watery consistencies first and work up to the thickest creams and oils last. More specifically, face wash goes first, followed by exfoliants like Dermalogica's Daily Microfoliant or Paula's Choice 2% BHA Liquid Exfoliant; toners or essences like Vichy's Pureté Thermale Perfecting Face Toner are up next; and then eye treatments (Amazon shoppers love LilyAna Naturals' Anti-Aging Eye Cream). Then you bring in acne or spot treatments like Versed's Nix It Complexion Solution, followed by serums or retinol, a moisturizer like Acure's Brightening Cream, and face oil—Radha's Rosehip Oil wins raves for reversing wrinkles. In the morning, top it all off with an SPF like Kinship's editor-loved Self Reflect Probiotic Moisturizing Sunscreen

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Credit: Dermstore

What ingredients to avoid in skincare?

Deciding which ingredients to avoid in skincare can be tricky, but based on the hormone-disrupting abilities of parabens, phthalates, benzophenones, and cyclic silicones like cyclopentasiloxane, it's safe to say those are worth avoiding for the risk of long-term health effects. Talc is another red flag, based on the FDA's finding of asbestos mixed in with the ingredient. 

In terms of irritants, The Campaign for Safe Cosmetics recommends avoiding methylisothiazolinone and methylchloroisothiazolinone, which frequently sensitize skin, and formaldehyde releasers like DMDM hydantoin, diazolidinyl urea, imidazolidinyl urea, and quaternium-15. Finally, experts recommend avoiding perfluorinated ingredients like perfluorohexane and pentafluoropropane, as they're PFAS associated with types of cancer

When to use vitamin C in skincare routine?

Unlike ingredients you have to carefully place in your routine, you can feel free to use vitamin C at any point. (Antioxidants: There's never a bad time.) Going by the advice above, in the morning you should use it after your face wash and toner (if you're a toner person); in the evening, slather it on post-exfoliant, toner, eye cream, and spot treatments. 

What does vitamin C do for your skin?

Truly, it's more like what doesn't vitamin C do for your skin? The ingredient stimulates collagen production for plumper, more bouncy skin and tackles signs of aging by repairing damage done by pollution and UV light. Dermatologist Arielle Nagler, MD, recommends everyone uses a vitamin C product in their routine, whether that's TruSkin's Vitamin C Facial Serum—Amazon's best-selling facial serum—or celebrity favorite Sunday Riley's C.E.O. Vitamin C Rich Hydration Cream. Whatever you choose, Jaliman recommends looking for a vitamin C concentration around 10 to 15 percent; ascorbic acid, magnesium ascorbyl phosphate, and sodium ascorbyl phosphate are all good options.   

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Credit: Amazon

When to use oil in skincare routine?

Oil tends to be on the heavier side, so use it to lock in your serum, retinol, and moisturizer. It should be your last step at night and second to last in the morning, topped only by sunscreen. If you're not sure where to start, jojoba oil is great for oily skin; Cliganic's organic one has the approval of nearly 33,000 shoppers. Reviewers in their 60s credit Health Priority's organic vitamin E oil for leaving them almost wrinkle-free, and rosehip oil is packed with vitamin A: Shoppers rave about the effects of Pura D'Or's iteration.   

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Credit: Amazon

How to add retinol in skincare routine?

To make the most of retinol without triggering dryness, Shari Lipner, MD, PhD, a dermatologist at New York-Presbyterian and Weill Cornell Medicine, says to gradually ease into the ingredient. A pea-size amount can treat your entire face, and she recommends using retinol every other day at first. Apply retinoids in the evening, since they can make you more sensitive to sun—and on that note, always use sunscreen when a retinol like Paula's Choice 1% Retinol Treatment is in your routine. If you want to be on the safe side, make an exception to the skincare order rule by mixing a pea-size amount of retinol with a dollop of moisturizer, which helps your skin acclimate with a technique called "buffering."  

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Credit: Paula's Choice

When to apply BHA in my skincare routine?  

Whether morning or night, you can feel free to use a beta hydroxy acid exfoliant like salicylic acid. It should be your first stop after cleanser, since the treatment increases cell turnover by loosening the bonds between healthy and dead skin cells—meaning anything you apply afterwards will penetrate better and help give you the greatest results possible. Looking to dip your toe? Benton's Aloe BHA Skin Toner mixes the exfoliant with skin-soothing aloe, while Biossance's Squalane + BHA Pore-Minimizing Toner brings in squalane to moisturize.

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Credit: Amazon

To buy: Benton Aloe BHA Skin Toner, $16 (was $19);