Both lactic acid and glycolic acid are AHAs, or alpha hydroxy acids. Glycolic acid is considered to be the stronger of the two, but stronger doesn’t always equal better. Both lactic acid and glycolic acid can be used at different concentrations to effectively target a host of skincare issues, from improving acne or skin texture, reducing fine lines and discoloration, and reversing sun damage and aging symptoms.
Lactic acid is an AHA, or an alpha hydroxy acid. It is naturally occurring in milk and is made when milk goes sour. Our body also creates it when it converts food into energy. Lactic acid as a solution is also used as a food additive as preservative or for flavor.
Other AHAs include glycolic acid, mandelic acid, and malic acid. Lactic acid is one of the most common type of AHA and is available in a wide range of concentrations, making it a great beginner and advanced alpha hydroxy acid. You can use it in a lower concentration when you’re starting out in your acid exfoliation journey as well as in stronger concentrations once your skin has become accustomed to chemical exfoliation.
Lactic acid can be found in concentrations as low as 1% to 50% or more but we do not recommend getting a double digit concentration if you’ve never used an alpha hydroxy acid before. Start with a low percentage like 5%, follow the directions to use sparingly every few weeks until your skin is used to acid exfoliation before trying a stronger lactic acid product.
All AHAs, including lactic acid, make your skin more vulnerable to sun damage. Your skin is extra sensitive to sun damage for up to 7 days after you use an AHA. So you must wear sunscreen while using an AHA like lactic acid. AHAs help reverse visible and invisible damage done by the sun’s ultraviolet rays and if you don’t use an sunscreen daily alongside AHA use, you risk canceling the positive effects of the AHA and experiencing further damage on top of it. So please use sunscreen daily!
As an AHA, Lactic acid benefits include exfoliation of top skin layers for better skin complexion and texture, decreasing skin scars and spots, and reducing fine lines. This article will compare lactic acid with glycolic acid, but if you want to learn more about AHAs or other types of AHAs, read our guide to AHAs.
Glycolic acid is an alpha hydroxy acid or AHA. It is naturally occuring in sugarcane and pineapples but many of the forms found in skincare products is created from scratch to make it a more stable ingredient with a longer shelf life.
Amongst the types of alpha hydroxy acids, glycolic acid has the smallest molecule size. This means that it is able penetrate deeper than other AHAs like lactic acid or mandelic acid, and so is the strongest of the alpha hydroxy acids.
So you should use glycolic acid carefully. Glycolic acid can be found in concentrations from 2% to 50% and more. Given that it is a highly penetrative acid, we highly recommend starting with a low concentration like 5% so that your skin can become accustomed to alpha hydroxy acid before moving onto a high concentration that your skin may not tolerate.
Using a high concentration of a powerful acid like glycolic acid without preparing your skin or building up tolerance can lead to a damaged moisture barrier, severe skin peeling, redness, burning, and irritation. In fact, you can literally give yourself 1st degree burns if you try to use a high % glycolic acid right off the bat. So build up tolerance slowly and use a lower concentration glycolic acid to protect your skin. In fact, using a lower concentration glycolic acid product more frequently over time will give you better results than a one time drastic use of a high percentage glycolic acid produce.
Like lactic acid, you must wear sunscreen everyday if you want to use an alpha hydroxy acid like glycolic acid. Protect your skin from further UV damage while you reverse existing UV damage. All alpha hydroxy acids increase your sun sensitivity for up to 7 days after use. If you don’t use sunscreen, you risk damaging your skin further instead of repairing it.
Glycolic acid offers the same benefits as lactic acid but at a greater strength than lactic acid. However, just because it is stronger doesn’t always make it the better way to repair scars, fine lines, skin texture and complexion. Depending on your skin, you may find that a less potent acid used more frequently works better for you.
This is a common question from people looking to choose one or the other for their skin issue: Lactic acid or glycolic acid – which one is better?
As we’ve mentioned, neither is a categorically better choice and each has its benefits. A lot has to do with your skin and its sensitivity.
Sensitive skin types or those dealing with a damaged moisture barrier and experiencing the highly irritated skin that is a result, might do better with lactic acid. Lactic acid offers the same benefits as its stronger sister, glycolic acid, but because it has a larger molecule size, it does not penetrate as deeply. People with sensitive skin will find lactic acid to be the gentler acid between two. Using lactic acid at a 5% or 10% concentration every few weeks will help you get the results you want in time without irritating your skin to the point of no return.
On the other hand, you may be an acid veteran and be looking for the next potent option, or you may have noticed that your skin is resilient and is able to tolerate exfoliation well. Glycolic acid is your friend, in this case. If you can tolerate it naturally or have built up your tolerance for it, glycolic acid offers a range of benefits at a much faster rate than lactic acid.
Technically you can. But they do the same thing as different concentrations and at a different time frame. We can’t think of a reason you would need to use two separate products of a lactic and a glycolic acid together, and you run a high risk of overdoing it and damaging your skin’s natural moisture barrier. It would be better to find which ones works better for your skin type and sensitivity and use that over the course of a few months and then reevaluate if you need a higher strength product or maybe a different one.
However, certain products may combine the two to make a combination peel or solution. Depending on your skin and the severity of the problem you are targeting, you may get great results from a combination because it is able to target the issue at two different penetrative depths. These types of peels or solutions are most commonly used in professional environments under the direction of an esthetician or dermatologist, but a few are available over the counter.
The next section will take a look at the various benefits of lactic acid, glycolic acid, and alpha hydroxy acids in general and draw from scientific research to compare the two acids.
They are both alpha hydroxy acids which work to remove top layers of skin and dead skin cells, a process that also unclogs pores. So both glycolic acid and lactic acid are effective in reducing and preventing acne by exfoliating to open comedones and remove blackheads and whiteheads.
In one study conducted on 248 Italian patients with mild to moderate acne, the patients were treated with alpha hydroxy acid twice a day for 60 days. This was a non randomized open study but it specifically looked at the effects of AHA on patients who had gone to a dermatologist for their acne issues and were prescribed an AHA cream either by itself or alongside another treatment. The results:
“The results of this study, while confirming the high tolerability and efficacy of this AHA cream in the treatment of mild/moderate acne, reasonably suggest its possible use also in monotherapy. Furthermore, its use can be reasonably hypothesized as a maintenance treatment after specific pharmacological treatment even in more severe acne types.” [source: Baldo A, Bezzola P, Curatolo S, Florio T, Lo Guzzo G, Lo Presti M, Sala GP, Serra F, Tonin E, Pellicano M, Pimpinelli N. (2010) G Ital Dermatol Venereol.]
Another study looked at the effect of AHAs on skin pore and comedone. A 4% AHA chemical peel that was part water, part glycolic acid and part lactic acid was used to treat a group of healthy women. The study measured pore area and number, counted comedones, and measured sebum production in a test and control group and found:
“4% AHA solution combined with a physical effect had rapidly improving effects on whiteheads and blackheads synergistically. Combined physical therapy may have more impact on pore size and seborrhoea.” The study showed that whiteheads, blackheads, sebum, and pore sized all decrease at a faster rate for the test group than the control group.” [source: Kim SJ, Baek JH, Koh JS, Bae MI, Lee SJ, Shin MK. (2015) Int J Cosmet Sci.]
So both glycolic acid and lactic acid have been shown to effectively treat current and prevent new acne.
Alpha hydroxy acids like lactic acid and glycolic acid help hydrate your skin in 2 different ways.
First, they slough off top layers of dead skin cells revealing new skin underneath. Now when you apply a moisturizer, you’re able to apply it directly onto skin’s surface on new skin cells.
And second, “an important epidermal effect is the increase of the water holding capacity due to AHA application along with an increase of skin hydration and skin turgor.” [source: Philipp Babilas, Ulrich Knie, Christoph Abels. (2012) Journal of the German Science of Dermatology.]
Alpha hydroxy acids are hydrophilic, meaning they attract and bind water to your skin’s surface, improving hydration and skin texture. Dry skin is usually a combination skin issue, in that it is usually accompanied by other issues such as irritation and discomfort, visibly scaly skin that sheds, and overall skin texture problems. Alpha hydroxy acid can help with many of these issues as well in addition to hydrating your skin and improving dry skin.
Both alpha hydroxy acids can be very effectively used to get rid of sun damaged skin symptoms like fine lines or melasma.
Even though glycolic acid is considered to be stronger because it has a smaller molecule size and so penetrates deeper, both can be used equally effectively. Using a low concentration acid, either lactic or glycolic acid, over the course of 6-8 weeks can give you incredible results comparable to a high concentration solution of just glycolic acid. In fact, this method can help you manage some less than savory side effects that come with using a high concentration acid like severe peeling or skin shedding.
Glycolic acid has been shown to be particularly effective in reducing melasma, a common effect of too much sun exposure. In one study conducted on Indian patients with melasma, glycolic acid showed promising results. Forty Indian patients with moderate to severe melasma were treated over a period of time with glycolic acid peels against a control group. The results:
“The group receiving the glycolic acid peel with topical regimen showed early and greater improvement than the group which was receiving topical regimen only…
This study concluded that combining topical regimen (2% hydroquinone, 1% hydrocortisone and 0.05% tretinoin) with serial glycolic acid peeling significantly enhances the therapeutic efficacy of glycolic acid peeling. The combination of glycolic acid peeling with the topical regimen is a highly effective, safe and promising therapeutic option in treatment of melasma.” [source: Chaudhary S, Dayal S. (2013) J Drugs Dermatol.]
Since lactic acid works in the same fundamental ways as glycolic acid, lactic acid can show similar results for melasma.
Alpha hydroxy acids like glycolic acid and lactic acid has also been shown to reduce fine lines and surface wrinkles by increasing collagen production in your skin.
In one study done on albino mice, glycolic acid successfully repaired sun damage. The mice were exposed to the sun’s UVB (a type of ultraviolet light) for 10 weeks and then a 15% glycolic acid was applied to their skin for the subsequent 10 weeks. The study paid attention to whether there was improvement in wrinkles and an increase in collagen production. The results:
“At treatment week 10, the glycolic acid-treated mice showed a significant decrease in wrinkle score, an increased thickness of the dermal repair zone, and an increase in the amount of collagen synthesized compared to vehicle (hydrophilic ointment base) treated mice… Topically applied glycolic acid may improve photoaging through modulation of collagen production.” [source: Moon SE1, Park SB, Ahn HT, Youn JI. (1999) Dermatol Surg.]
Both lactic and glycolic acid can help improve hyperpigmentation from photodamage (sun damage) or acne scars because they help speed up skin cell turnover and reveal new skin underneath.
In a study conducted on 33 women with a mean age of 55.5 years who had significant sun damage like age spots, freckles and other skin discolorations. The patients were treated twice daily with an alpha hydroxy acid cream for a period of 8 weeks. The results showed that:
“The appearance of age-related hand pigmentation characteristics were significantly improved at 4 and 8 weeks of treatment. Subjects reported post-treatment improvements in other characteristics associated with healthy skin. [source: Gold MH, Gallagher C. (2013) J Drugs Dermatol]
Both glycolic acid and lactic acid can help reverse skin darkening that are superficial like sun tans or with tinted tanning lotions by removing top layers of skin to reveal new skin that is your natural and original skin color.
Please note an important distinction here. Neither of these alpha hydroxy acids will lighten your skin more than your natural skin, only lightens tanned or discolored skin back to your original skin.
So if you’re looking to lighten your skin to a shade that is lighter than your natural tone, then you may not have much success with alpha hydroxy acids. However, if you are looking to remove a tan or other discoloration, then alpha hydroxy acids can provide great results also found in scientific studies that we discussed in previous sections.
In conclusion, both glycolic acid and lactic acid can offer similarly excellent results in lightening skin discoloration like tans or scars, improve skin texture and complexion, and reduce and prevent acne.
To learn more about hydroxy acids, check out our introduction to AHAs (alpha hydroxy acids) or our complete guide to BHAs (beta hydroxy acids).
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