Lactic Acid vs Glycolic Acid | Which Acid Is Better?

As you age, your skin’s natural exfoliation process slows down which can leave your skin looking rough and dull with exaggerated fine lines and wrinkles. To keep your skin looking smooth and glowing, exfoliation is essential. With such a wide range of chemical exfoliants available, it can be hard to work out which one is right for you, or even to know what each exfoliant does. For example, which is better – lactic acid vs glycolic acid?

What’s the difference between lactic acid and glycolic acid anyway?

Chemical Exfoliation

Chemical exfoliants increase the rate that your skin naturally exfoliates itself. They do this by breaking down the bonds that hold your dead skin cells together which makes it easier for them to be shed from the surface of your skin.

There are three main types of chemical exfoliant; alpha-hydroxy acids (AHAs), beta-hydroxy acids (BHAs), and polyhydroxy acids (PHAs).

Lactic Acid

Lactic acid is an AHA that’s made from the sugars found in milk (lactose). It is naturally present in your skin as part of the natural moisturizing factors (NMFs) which means that it makes an excellent moisturizer. 

It’s generally less irritating than glycolic acid (depending on product formulation) and, due to its hydrating properties, may be more suitable if you have drier skin.

The main benefit of AHAs, like lactic acid, is that they help exfoliate your skin. 

As a result of this, lactic acid also helps to:

• Improve fine lines and wrinkles
• Improve skin texture
• Brighten skin
• Reduce enlarged pores

Glycolic Acid

Glycolic acid is an AHA that is made from the sugar cane plant. It’s thought that glycolic acid exfoliates your skin by removing the calcium ions from the bonds that hold your dead skin cells together which weakens them and allows exfoliation to take place.

Some of the benefits of glycolic acid include:

• Improving skin texture
• Reducing hyperpigmentation
• Brightening skin
• Improving acne
• Boosting collagen production to improve fine lines and wrinkles
• Reducing the appearance of enlarged pores

Glycolic acid has the lowest molecular weight of all the AHAs which means that it penetrates your skin with more ease. However, because of this, it’s also more likely to cause skin irritation.

Lactic Acid vs Glycolic Acid

So which is better suited to your skin type and the conditions you wish to treat?

One key difference between lactic acid vs glycolic acid is that they have differing molecular weights. Glycolic acid has a smaller molecular weight (72) than lactic acid (90) which means that it can penetrate your skin with more ease – including the deeper layer of your skin (your dermis).

Generally speaking, this means that glycolic acid tends to be more effective than lactic acid. However, the effectiveness of AHAs is also influenced by the pH and concentration (%) of the formula/product, as well as how long it’s applied to your skin for. 

Image Source: Tang, S. & Yang, J. (2018). Dual Effects of Alpha Hydroxy Acids on the Skin.

Some research has found that lactic acid is equally as effective as glycolic acid when it comes to improving skin hydration, fine lines, and wrinkles but causes less skin irritation. Lactic acid peels were also better tolerated than glycolic acid peels while providing similar improvements in melasma. So, if you have sensitive skin, lactic acid would probably be the better option.

In addition, as lactic acid is naturally found in your skin’s natural moisturizing factors (NMFs) and its bacteria found in your skin microbiome, it may be the better option for overall skin health – especially if you have drier skin.

However, glycolic acid can also boost hydration by increasing the natural production of glycosaminoglycans (e.g. hyaluronic acid) in your skin.

One clinical study compared lactic acid vs glycolic acid creams (both 8% concentration) and found that 71% of people using the lactic acid cream and 76% of people using the glycolic acid cream saw an overall improvement to their sun damaged skin – suggesting that both creams were equally effective. Both creams improved overall sun damage and skin sallowness but lactic acid also improved mottled pigmentation and skin roughness.

Other research found that there was higher patient satisfaction with lactic acid vs glycolic acid peels.

So overall, when it comes to lactic acid vs glycolic acid, glycolic acid should be more effective in theory. However, research suggests that this is not necessarily the case and that lactic acid may be equally as effective, if not better than glycolic acid.

It’s important to note that, while studies directly comparing lactic acid vs glycolic acid seem to favor lactic acid, there’s generally more overall research behind glycolic acid than there is for lactic acid.

In other words, glycolic acid is the more tried-and-tested ingredient.

Can You Use Lactic Acid and Glycolic Acid Together?

Lactic acid and glycolic acid can be used together but it’s better to avoid layering them yourself. Instead, look for a well-formulated multi-ingredient product to reduce the risk of skin irritation and purging.

For example, a multi-ingredient product containing 1% lactic acid and 1% glycolic acid alongside soothing antioxidants (niacinamide and vitamin E) was effective at improving fine lines, texture, and skin elasticity. It was also well tolerated although some people experienced a stinging sensation after a week of use.

How To Use Lactic Acid vs Glycolic Acid

Both lactic acid and glycolic acid should be applied to dry skin a maximum of three times per week to avoid irritation. If your skin isn’t particularly sensitive then you could use both exfoliants together, although it’s far safer to use a multi-ingredient product than to layer lactic acid and glycolic acid yourself.

AHAs like lactic acid and glycolic acid increase your skin’s sensitivity to the sun and can leave you with worse skin damage than you started with. For this reason, it’s absolutely essential that you’re using sunscreen everyday.

It’s also better to use acids in your nighttime routine, especially as your skin’s natural exfoliation process is higher overnight.

Lactic acid and glycolic acid are considered safe to use in over-the-counter (OTC) products at concentrations up to 10% and a pH of 3.5 and in professional peels at concentrations up to 30% and a pH of 3.0.

However, if you’re new to acids, start with lower concentrations (e.g. 5%) of lactic or glycolic acid and gradually increase the strength as your skin tolerates. This can help prevent irritation and reduce the severity of skin purging (acne breakouts caused by increasing cellular turnover).

Make sure to use plenty of moisturizer too!

Although it’s better to apply acids to dry skin, you can also apply them on top of your moisturizer. This is referred to as ‘buffering’ as it takes the acids longer to penetrate your skin which can help reduce irritation.

Acids only help to exfoliate the very top layer of your skin (your stratum corneum). For maximum effectiveness, use acids alongside a retinoid as retinoids increase the rate that your skin produces new skin cells and brings them to the surface of your skin. When used together, acids and retinoids can enhance each others effects – but you need to be careful that this combination doesn’t damage your skin barrier and irritate your skin.

Lactic Acid vs Glycolic Acid – The Bottom Line

Lactic acid and glycolic acid are both AHAs that work in a similar way and offer similar benefits for your skin. When directly comparing lactic acid vs glycolic acid, lactic acid usually proves to be more effective with less side effects (redness, irritation, etc.). Therefore, if you have dry or sensitive skin, lactic acid is probably the better option for you. However, if you prefer the more tried-and-tested option, glycolic acid would be the better choice as there is more research behind the ingredient.

At the end of the day, your skin is unique to you and you may respond differently to lactic acid vs glycolic acid.