Exfoliating is key to boosting your skin’s natural cell renewal, leaving you with a smoother, brighter complexion. By clearing away dead skin cells, it helps unclog pores, prevents dirt and oil buildup, and makes your other skincare products work even better. But with popular exfoliants like glycolic acid and urea on the market, how do you know which one is right for you?

What Is Urea?

Urea, a hygroscopic molecule and part of our skin’s natural moisturizing factors (NMF), plays a crucial role in keeping the stratum corneum healthy and hydrated. As a naturally occurring substance in the skin, urea acts as an effective humectant and is commonly found in moisturizers. At higher concentrations (>10%), it also has keratolytic properties, meaning it can promote skin cell turnover, making it a versatile ingredient for both hydration and gentle exfoliation. Urea has also been shown to enhance the skin’s ability to absorb other active ingredients in a formula. Prequel’s Advanced Relief Moisturizing Milk uses urea as both a skin humectant and texture enhancer, making it safe for daily use.

In clinical settings, high-percentage urea has been used to treat various skin conditions like atopic dermatitis, psoriasis, and seborrheic dermatitis. Though it’s not a new ingredient, urea is becoming increasingly popular in the mass market— and for good reason, as it’s highly effective! As formulators, we pay close attention to factors like pH and temperature when working with urea. But when formulated correctly, urea is a powerful ingredient that truly enhances skincare products.

What Type Of Skin Is Urea Best For?

While urea is suitable for all skin types, it delivers the most noticeable results for dry and flaky skin due to its humectant properties. Urea is generally known to be suitable for sensitive skin, however a patch test is always recommended when venturing out into new skincare actives.

How Does Urea Work at Different Percentages/Strengths?

The function of urea in a personal care product varies based on its use level. Below 10% urea primarily acts as a humectant, moisturizing the skin and optimizing the skin barrier. This hygroscopic material keeps the skin hydrated and water retained in the outermost layers of the skin. This is how it functions as part of the skin’s NMF.

When used at 10% and above, urea functions more as a keratolytic agent breaking down the connection between dead skin cells to smooth scaly, dry and flaky skin. Concentrations between 20-30% can help reduce itching, break down keratin, and decrease the thickness of the outermost layer of skin. This is beneficial for skin conditions such as psoriasis that exhibit abnormal keratinocyte proliferation and differentiation.

Even higher concentrations of urea can be found in foot care products because urea exhibits a proteolytic nature breaking down proteins at high concentrations. You can find it in callus remover products when combined with salicylic acid, the active pharmaceutical ingredient noted on the monograph for corn and callus remover.

What Is Glycolic Acid?

Glycolic acid, unlike urea, is not part of our natural moisturizing factors (NMF), but when used correctly, it can be a valuable addition to your skincare routine for maintaining a healthy skin barrier. As an alpha-hydroxy acid (AHA), typically derived from fruits and water-soluble, glycolic acid promotes the shedding of dead skin cells, also known as desquamation, by loosening the bonds between them. This accelerates exfoliation, improving the visual signs of photo-aging, fine lines, dark spots, and congested skin.

Among AHAs, glycolic acid has the smallest molecule, allowing it to soak into the skin more efficiently and perform faster. Glycolic acid is also known to induce some inflammation or erythema if not used properly, which is why it is recommended to start with a lower percentage and work your tolerance level up. In clinical settings, higher concentrations of glycolic acid have also been shown to promote collagen synthesis and increase epidermal and dermal hyaluronic acid levels.

What Type Of Skin Is Glycolic Acid Best For?

Glycolic acid can be used on all skin types depending on the concentration in a product but it is especially beneficial for dull, photoaged skin. It can brighten the skin, reducing topical skin discoloration and hyperpigmentation while also addressing fine lines and wrinkles. Unlike salicylic acid which can also even skin tone and texture, glycolic acid does not reduce sebum production so it can be used by those with dry skin.

It’s also important to be aware of a product’s pH because glycolic acid’s efficacy hinges on the pH of the product. Glycolic acid’s pKa is around 3.83 so at a pH of 3.83, half of the concentration of glycolic acid is in the nonionic “active” form while the other half is charged which is not favorable for skin penetration and therefore less efficacious. The goal is to have an acidic product with a pH low enough to favor glycolic acid soaking into the skin but not so low that it induces inflammation, irritation, and erythema. If you have sensitive skin, it is recommended to start at a lower dosage or use glycolic acid in a rinse off formula for shorter contact time. However, if your skin can tolerate it, a higher percentage (between 5-15%) can be great for reducing the appearance of uneven skin texture, fine lines, and wrinkles. Using a milky toner, cream, or moisturizer with glycolic acid can help buffer and offset potential irritation as opposed to using a solution or clear toner containing glycolic acid.

Do not forget: you must wear sunscreen when using an AHA! You don’t want to undo all the benefits due to the negative effects of sun exposure.

Between Urea and Glycolic Acid, Which Is Better for Skin Smoothing/Exfoliation?

If your primary concern is sensitive, dry, flaky skin, urea is a better ingredient to incorporate into your daily skincare routine, as it helps improve both your skin barrier and texture.

However, if you're focused on addressing topical signs of photo-aging, dark spots, and fine lines while also wanting to improve skin texture, glycolic acid may be a better alternative.

Who says you can’t use both? If your skin can tolerate it, combining a glycolic acid toner with a urea-based moisturizer, like the one from Prequel, can be a great way to achieve hydrated and supple skin.

DISCLAIMER: All skin care articles are intended to help educate on specific ingredients and skin care topics. Our articles are written to be informative and informational. Any reference to a specific patient experience is not a medical suggestion for treatment. Please note that any Prequel products with referenced ingredients are formulated for Cosmetic Use Only and NOT intended as replacements for physician advice and/or pharmaceutical product recommendations.