Kiehl’s Over-Night Biological Peel: A Good Alternative To Glycolic Acid?

by Gio

kiehl's over night biological peel

Glycolic acid is my favourite exfoliating ingredient. It removes dead skin cells, helps reduce dark spots and the appearance of wrinkles, moistuirizes skin, and even boosts collagen production. Pretty impressive, isn’t it?

So, when I came across Kiehl’s Over-Night Biological Peel, which claims to be as potent as a 10% glycolic acid product, I was intrigued. What have they put in it to make it so special? And, most importantly, how well does it work?

What Kiehl’s Says

Helps to gently renew skin, leaving texture softer, more even, and vibrant after first use.
With continued use, helps reduce the look of pore size and ameliorate the effects of free-radical and photo-damage.

Ingredient Analysis

Urea molecular structure


So, what’s this amazing ingredient that’s as powerful as glycolic acid? Urea. Yep, that stuff found in urine. But don’t worry. The type used in cosmetics is synthetically made in a lab, so you won’t be putting anything icky on your face.

Urea, which is also naturally found in the skin, where it helps to maintain moisture balance (it ensure skin remains soft and supple), has a couple of things in common with glycolic acid. Both are exfoliants and humectants.

As an exfoliant, urea helps dissolve the bonds that bind skin cells together, thus allowing them to slough off. This helps reduce dry patches, uneven skintone, and even the appearance of wrinkles. But, unlike glycolic acid, urea doesn’t need to be formulated at a specific ph to work.

As a humectant, urea helps draw moisture from the environment into the skin. Able to absorbs and retain water, it reduces the amount that’s lost through the skin. As a result, dry patches are healed and skin is once again soft and smooth.

The catch? When used in high doses, urea can cause a stinging sensation upon application, and even irritate skin. Because of this, I’m a bit hesitant to recommend this exfoliant to those with sensitive skin. But, everyone else who feels adventurous and wants to try an alternative to glycolic acid may really enjoy it.

glycerin molecular structure

Glycerin And Sodium Hyaluronate

Urea is not the only humectant present in the formula. The peel also contains Glycerin and Sodium Hyaluronate. The latter is particularly beneficial because it can hold 10x its weight in water, and works well both in high and low humidity conditions.

All these humectants make this formula a godsend for people with dry skin. The peel will help banish toughness and flaking and keep your skin in top shape.


Hydroxyethylpiperazine Ethane Sulfonic Acid

HEPES, which is short for Hydroxyethylpiperazine Ethane Sulfonic Acid (what a mouthful!), is a buffer. That means it is used to maintain the formulation at a skin-friendly ph. This may also helps reduce the risk of any potential irritation caused by urea.

Further Considerations On The Formula

Kiehl’s Over-Night Biological Peel is a silicone-based formula. But not all silicones are created equal. Cyclopentasiloxane is very volatile. That means it quickly helps the texture spread evenly on the skin before evaporating. Other silicones, such as Cetyl PEG/PPG-10/1 Dimethicone, stay on the skin (but without suffocating it!), giving it a soft and smooth look and feel.

Full Ingredient List

Water, Cyclopentasiloxane, Urea, Hydroxyethylpiperazine Ethane Sulfonic Acid, Glycerin, C12-15 Alkyl Benzoate, Propylene Glycol, Cetyl PEG/PPG-10/1 Dimethicone, Bis-PEG/PPG-14/14 Dimethicone, Triethanolamine, Phenoxyethanol, Sodium Chloride, Sodium Hyaluronate, Sodium PCA, Methylparaben, Propylparaben, Ethylparaben, Isobutylparaben, Butylparaben

The Bottom Line

Particularly suitable for dry skin, silicone-based Kiehl’s Over-Night Biological Peel exfoliates and moisturizes skin at the same time. Although expensive, it is a nice alternative for people who can’t use glycolic acid or who want to try something new.

Have you tried Kiehl’s Over-Night Biological Peel?

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