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Our Guide To Lactic Acid vs. Glycolic Acid

How Lactic Acid and Glycolic Acid Differ

Unless you’re a cosmetic chemist, it’s unlikely you’re familiar with all the different acids used in skincare—there are dozens (if not more). While the thought of putting any acid on your skin can seem a bit off-putting, the reality is that skin-friendly acids can have a place in virtually any skincare routine. The key, of course, is to find one suitable for your skin type and unique skin concerns. This can be challenging if you’re not familiar with the different kinds of skincare acids or how they work. But fret not, we’re here to help. 

Here, we’re going over two of the most widely-used acids in skincare—namely, lactic acid and glycolic acid. Both are chemical exfoliants that can help address a wide range of skin tone and texture concerns, but their benefits and uses differ in a few ways. Ahead, we’ll give you the full rundown on lactic acid and glycolic acid and explain how each can benefit your skin. We’ll also provide recommendations on which acid to use based on your skin type and introduce to you a few Kiehl’s staples that you can incorporate into your regular skincare routine. 

What Is Lactic Acid?

Lactic acid is a relatively mild alpha-hydroxy acid (AHA) found in the body and commonly used in skincare. It’s a primary constituent of the skin’s natural moisture barrier and helps maintain adequate hydration. Lactic acid used in skincare formulations is typically derived from fermented dairy products, like milk or cheese.

What Are The Benefits of Lactic Acid?

In skincare, lactic acid is mainly used as a chemical exfoliant. It works by helping to remove the topmost layer of dead skin cells to improve the skin’s appearance. It’s most frequently used to help address skin tone and texture concerns, such as fine lines and dullness. Some research also suggests that lactic acid can help firm and plump the skin.I These benefits make lactic acid a highly popular ingredient in anti-aging skincare products

You’ll find lactic acid in Milk-Peel Gentle Exfoliating Toner, alongside lipo-hydroxy acid and a blend of skin-friendly emollient moisturizers. The mild yet effective toner helps exfoliate while restoring skin’s natural moisture levels for a hydrated, comfortable feel. The powerful daily toner is clinically-proven to visibly smooth, soften, and brighten the skin and is suitable for all skin types, even sensitive skin.* We recommend applying this powerful toner to your face and neck twice daily after cleansing for more refined, clearer-looking skin with continued use.

*Results based on expert grading in a clinical study of 44 panelists, ages 30-50, after four weeks of use.

What Is Glycolic Acid?

Glycolic acid is a naturally-occurring acid derived from sugarcane and other sugar-rich plant sources. Like lactic acid, it is frequently used in skincare to address age-related skin concerns, like fine lines and wrinkles. However, glycolic acid is among the more potent AHAs used in skincare. As such, high concentrations of glycolic acid can cause irritation, especially for those with sensitive or reactive skin.

What Are The Benefits of Glycolic Acid?

As we mentioned earlier, glycolic acid is often used in skincare products designed to help address the visible signs of aging. Some research suggests topical glycolic acid can encourage your body’s production of essential compounds, such as collagen and hyaluronic acid.II These benefits, coupled with its antibacterial properties and exfoliative activity, also make glycolic acid helpful in treating blemishes and post-blemish marks.

To reap the benefits of glycolic acid, we recommend reaching for Clearly Corrective Brightening & Smoothing Moisture Treatment. This daily moisturizer, which also contains vitamin C, provides continuous 24-hour hydration while helping to smooth and brighten dull, uneven-looking skin. It’s clinically-demonstrated to help correct the appearance of skin discolorations and rough texture to improve skin’s overall clarity.* The gentle formula is suitable for all skin types and can be used daily for clearer, brighter-looking skin.

*Results based upon a clinical study of the upper layers of the skin.

Clearly Corrective Brightening & Smoothing Moisture Treatment

What Is The Difference Between Lactic Acid and Glycolic Acid?

When it comes to picking which acid you want to use in your skincare routine, both lactic acid and glycolic acid have their benefits. There are a few different factors you’ll want to consider, though, including your skin type, the skin concerns you’re looking to address, and what other ingredients you use in your routine. For example, unless you’re accustomed to regular exfoliation, you’ll want to start with gentler products that provide results over time to minimize the risk of irritating your skin.

If you’re looking to try a gentle AHA, we recommend adding Ferulic Brew Rejuvenating Treatment Essence to your skincare routine. This water-light facial essence with lactic acid and ferulic acid absorbs quickly to visibly refine the skin’s texture. The antioxidant-rich formula helps strengthen the skin’s natural moisture barrier and protect against damaging free radicals that can contribute to early signs of aging. It also helps prepare your skin for the rest of your routine and promotes a more radiant appearance over time. 

If you’re highly sensitive, you may prefer to start with a milder acid, such as phytic acid. You’ll find this AHA in Nightly Refining Micro-Peel Concentrate, a serum-light overnight peel suitable even for sensitive skin. The non-irritating formula gently exfoliates and refreshes your skin while you sleep. It’s clinically-demonstrated to accelerate skin cell turnover and helps visibly refine rough skin texture over time.* Use it nightly as part of your regular nighttime skincare routine for smooth, radiant-looking skin. 

*Based on an instrumental test within surface layers.

Can You Use Lactic Acid and Glycolic Acid Together?

You can use lactic and glycolic acids together if they’re found in the same formula. To boost your skincare routine and visibly improve your skin tone and texture, we recommend Clearly Corrective Accelerated Clarity Renewing Ampoules. This effective system includes 28 individual ampoules, one for your morning and nighttime routine. Each ampoule contains a highly-concentrated serum formulated with a blend of AHAs, including lactic, phytic, and glycolic acids. When used as directed, the two-week regimen helps improve the appearance of dullness and encourages skin’s natural cell turnover for smoother-looking skin. It’s clinically-demonstrated to brighten the skin by 33% and rejuvenates the skin for a more radiant appearance.* Despite its potency, the targeted treatment system is suitable for all skin types and can be used whenever your routine needs a little extra oomph. 

*Based on expert grading in a two-week clinical study of 85 panelists in Brazil.

Note: If you’re using any chemical exfoliant in your skincare routine, sunscreen is essential. Acids—and AHAs like glycolic and lactic acid in particular—are known to increase your sensitivity to the sun, making you more prone to developing painful sunburns. 

To protect your skin, reach for a mild broad-spectrum sunscreen, like Super Fluid Daily UV Defense 50+. This antioxidant-rich formula protects against damaging UV rays and free radicals caused by exposure to environmental aggressors, like air pollution. It's non-greasy and absorbs quickly, leaving skin with a matte finish. 

If you prefer mineral sunscreen, try Super Fluid Daily UV Mineral Defense. It provides long-lasting SPF 50 protection against UVA and UVB rays and is suitable for all skin types, even highly sensitive and acne-prone skin.

Next: The Best Tips For Youthful-Looking Skin

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