Today, I’m going to discuss the SkinCeuticals Glycolic 10 Renew Overnight.
Does this product live up to its claims? Let’s find out. ⭐
ⓘ In today’s post, I’ll share my 2¢ on SkinCeuticals Glycolic 10 Renew Overnight!
SkinCeuticals Glycolic 10 Renew Overnight
SkinCeuticals is a brand that I always recommend to my readers because of the company’s commitment to science-based skincare and history of product innovation (for example, they almost single-handedly created the “vitamin C serum” category with their award-winning and patent-protected bestselling vitamin C serum, the SkinCeuticals C E Ferulic).
The Glycolic 10 Renewal Overnight is another one of the company’s innovative products supported by both medical research and clinical trials (a single-center, 8-week study on 50 women).
This glycolic lotion features 10% Glycolic Acid (Free Acid Value), 2% Phytic Acid, and a 1% Soothing Complex of natural oils and botanical extracts, including Jojoba Oil and Sunflower Seed Oil.
These ingredients work together to help remove dead skin cells, promote a healthier and more radiant complexion, and reduce the appearance of discoloration and uneven skin tone.
Well, the reason is that glycolic acid, like all acids, dissociates (“splits”) in water-based solutions into two separate molecules: a Free Acid Form (no charge) and an Ionized Form (negative charge).
Here’s an excellent illustration by LabMuffin of this chemical reaction (and she has a great article that explains the importance of free acid value in relation to a formula’s pH level).
In this diagram, the free acid form of glycolic acid is on the left side while the dissociated products, namely a hydrogen ion (+) and conjugate base (-), are on the right side:
- We are primarily interested in the left side of this equation because the free acid form is the one that can actually penetrate our (oily) skin barrier thanks to its high oil-solubility. 👍
- In contrast, the ionized form does not penetrate our skin barrier very well due to its polarity (negative charge), which means it’s very water-soluble but not very oil-soluble. 👎
Most glycolic acid products on the market only disclose the overall concentration, even though a significant portion actually dissociates into an ionized form (which isn’t very useful for your skin).
That’s why the “true concentration” of glycolic acid is indicated by the Free Acid Value as this only counts the free acid forms of glycolic acid as a percentage of the total solution.
SkinCeuticals Glycolic 10 Renew Overnight has a free acid value of 10% glycolic acid at a pH of 3.5, which is the equivalent of about 14.75% glycolic acid when expressed as an overall concentration (source of calculation: LabMuffin Free Acid Value Calculator).
Finally, the last part of this puzzle is the pH level (potential for hydrogen). pH expresses the concentration of hydrogen ions in a solution in an inverse and logarithmic manner:
- pH = -log (Concentration of Hydrogen Ions)
For example, suppose we had a solution with 1% hydrogen ions:
- Then, the pH = -log (0.01), which is pH = 2 (very acidic)
But now, suppose we had a solution with 0.0000000001% hydrogen ions:
- Then, the pH = -log (0.000000000001), which is pH = 14 (very basic)
The pH level is important because it directly impacts the concentration of free acids in equilibrium:
- At low pH levels, there’s a high concentration of hydrogen ions which means the H+ ions will “bump” into more conjugate bases and form more free acids. 👍
- At high pH levels, there’s a low concentration of hydrogen ions and the opposite occurs. The H+ ions “bump” into fewer conjugate bases and form fewer free acids. 👎
However, we also don’t want a really low pH either as this would cause irritation and sensitivity.
When the pH is around the pKa, the formula remains stable (i.e. in equilibrium) and the free acid effectiveness is maximized while potential side effects are minimized (source: The Ordinary).
The pH of Glycolic 10 Renew Overnight is 3.5 which is a suitable level for acid effectiveness. 🤗
In terms of additional ingredients, 2% Phytic Acid helps exfoliate and brighten your skin while a 1% Soothing Complex of natural oils and botanical extracts seals in hydration and reduces irritation.
SkinCeuticals cites the following clinical results from an 8-week study on 50 women (ages 35-64):
- 36% average improvement in radiance
- 37% average improvement in skin texture
- 19% average improvement in skin tone
These results were collected through light imaging analysis at baseline and weeks 2, 4, 6, and 8.
My main critique of this study is that it did not compare the efficacy of Glycolic 10 Renew Overnight to another product, such as a generic AHA cream or placebo cream.
This would allow for a better analysis of how much Glycolic 10 Renew Overnight actually made a difference, since some skin problems, like hyperpigmentation, tend to resolve on its own over time.
- Many said their skin felt smoother, more hydrated, and less pigmented
- Some noticed improvements in skin brightness, pore sizes, smile lines, and dry patches
- Some switched to Glycolic 10 Renew Overnight from retinol and had no issues with it
- Almost all said this product did not cause any skin irritation, even those with sensitive skin
On the other hand, the most common complaint was the product packaging as the glycolic lotion can easily drip out of the tube. For this reason, I recommend transferring it to a pump bottle instead.
My Verdict: Not all glycolic acid products are created equal. The percentage on the label doesn’t always reflect the “true concentration” of glycolic acid due to its dissociation into an ionized form. SkinCeuticals Glycolic 10 Renew Overnight features true 10% Glycolic Acid (Free Acid Value) to help exfoliate and hydrate your skin for a brighter, clearer, and smoother complexion. 😊