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John Su the Science Guy

Should L-Ascorbic Acid and Glycolic Acid Be Used Together?

A while back, several readers brought this article to my attention. In it, the author Dr. Cynthia Bailey states that, “… vitamin C and glycolic acid can’t both be on the skin at the same time anyway.” The readers wanted to know if there was any truth to this statement.

Is There Any Evidence of a Negative Interaction?

Want to fight?

Want to fight?

Honestly, I have no idea why Dr. Bailey would say that. There is absolutely no documentation that supports her claim. Furthermore, when she responds to the various people asking her about it, she doesn’t show any evidence nor explain WHY they can’t be used together. I can think of no reason why they can’t be used together, except for the fact that some glycolic acid (GA) products are formulated with a pH above 3.5; they don’t typically go above 4.0 however.

Now, a pH of 3.5 or less is recommended for L-ascorbic acid (LAA) to properly penetrate into the skin. However, that number isn’t absolute. The diction makes it sound like a product with a pH of like 3.51 would be completely useless. And that’s not true at all. LAA is like any acid; it obeys all the same rules; most importantly that the rates of dissociation arenot linear by any means. In fact, the acid dissociation constant (pKa) of LAA’s is 4.17, which is higher than GA’s pKa of 3.83, meaning that it actually takes a less acidic pH for a given percent of GA to dissociate and function in comparison to the same percent of LAA.

Some More Reassurance

If that’s not enough to ease your doubts, consider this:

Skinceuticals C + AHA contains both ingredients.

Skinceuticals C + AHA contains both ingredients.

Dr. Bailey quotes, “L-ascorbic acid requires a pH of 3.5 or less to penetrate the skin.” That fact was taken from studies done by the people behind the brand Skinceuticals, including this one on on vitamins C, E and ferulic acid. Now, if LAA isn’t compatible with GA, why in the WORLD would Skinceuticals include a product that contains BOTH ingredients?! Clearly, they can be used together.

Like with anything, just make sure not to irritate the skin. When using LAA and GA together, that may increase chances of irritation. But keep in mind that irritation is a very personal thing; it will vary from person to person. Oh, and this applies to using LAA with other hydroxy acids like salicylic acid.

***Note that If this information looks familiar, I did talk about this rather extensively in replies to the same readers that mentioned this issue. But I figured that I’d make this a post so more people will see this.

About John

The Triple Helixian is an unbiased science and research-based site that attempts to clarify and elucidate questions about skin care, while aspiring to be the most thorough and complete source of information.


14 thoughts on “Should L-Ascorbic Acid and Glycolic Acid Be Used Together?

  1. I have a quick question. Can you pair up Vitamin C serum 15% Ascorbic Acid with Finacea? The one I am looking at is Dr. Jessica Wu Vivid Intense 15% Vitamin C Serum.

    Posted by Ann | August 20, 2014, 4:11 pm
  2. Hi John,

    Great article. I have sensitive skin so I never attempt to use Glycolic and L-Ascorbic acid together.

    I have a question regarding L-Ascorbic acid. I know it’s great for a lot of things, chiefly anti-aging. I have sensitive skin. Currently, I use Retin-A for anti-aging at night and Finacea for some mild inflammatory skin issue (I don’t have Rosacea) and skin brightening in the morning per my derm. I use niacinamide moisturizers to combat the irration issue with a very bland baby mineral sunblock (my skin cannot tolerate any chemical sunscreen and heavy oil).

    I have tried L-Ascorbic acid serums in different concentrations with silicone or water base on alternating mornings when I don’t use Finacea. However, the serums are too acidic and exfoliating for me, as my skin is thin. What would be a good, non-irritating alternative while reaping anti-aging benefits? I am looking for something with a short ingredient list, since my skin cannot tolerate a lot of actives at one time.

    I was looking at DHC Vitamin C Essence with 8% magnesium ascorbyl phosphate. I don’t know if this product will help and how to incorporate a non-irritating Vitamin C product into my current skincare routine with Retin-A, Finacea, and niacinamide moisturizers.

    If you can shed some light, I would really appreciate it. Thanks.

    Posted by Ann | March 3, 2013, 12:15 pm
    • Thanks Ana!

      Yes, if the DHC in fact contains 8%, that product would be a great option. I’ve actually never even heard of that brand, but the ingredients look sound nevertheless. And like I said, if it does actually contain 8%, then nice find!

      Give it a try, and please let me know your thoughts on it!

      Posted by John | March 3, 2013, 7:02 pm
      • Thanks John. I think I am gonna skip this product. It’s too watery. I don’t know much about the company to put my whole faith on the product. I guess I am gonna have to take out Vitamin C out of my whole skincare routine….

        Posted by Ann | March 4, 2013, 7:33 am
        • Ooh okay. I wish you’d still try it and lt us know how you like it. Is there something wrong with it being too watery? How do you know it’s too watery if you haven’t tried it?

          Also, I did some quick research, and DHC is actually quite a large and popular Japanese brand. They’e apparently famous for their cleansing oil. I don’t know if that helps you, but yeah, please let me know if I can be of further assistance.

          Posted by John | March 4, 2013, 11:58 pm
          • I actually got a sample of the product. It’s very watery like a toner. I guess because I have had bad experience with Vitamin C product due to my sensitive skin, I am too scared to put it on my face. I am gonna put it on my neck to see, now you encourage me to try it. 🙂 This product has a short list of ingredients with MAP, so I can know for sure if my skin is sensitive to even Vitamin C derivatives. But….is 8% of MAP effective enough to make a difference on the skin? Paula’s review on this product is good. I am still a bit weary and paranoid since I don’t know much about this company. Thanks.

            Posted by ANN | March 5, 2013, 7:53 am
            • Oh nice. Well it can’t hurt to try it on a less sensitive area.

              And I’m pretty sure 8% MAP would make a difference, especially considering how sensitive you are to L-ascorbic acid. And even if it doesn’t work out for you, there are other vitamin C derivatives to consider such as tetrahexyldecyl ascorbate AKA ascorbyl tetraisopalmitate.

              Let me know what you think of the DHC after trying it. Also, could you compare the texture of it to something you already own?

              Posted by John | March 5, 2013, 12:57 pm
            • I started using DHC Vitamin C Essence a few days ago after getting irritated by Skinceuticals CE Ferulic, and so far so good. The ingredient list is very simple, and it doesn’t seem to contain fillers or thickening agents. I guess that’s why it’s extremely watery–it looks and feels like water. Just to make sure it wasn’t actually water, I put a drop on my tongue, and nope, not water! LOL

              I was going to buy Dermalogica’s MAP-15 Regenerator because that also contains magnesium ascorbyl phosphate, but I contacted the company for the percentage, and they refused to say. I asked if the 15 in the name stood for 15%, but they again said they weren’t going to divulge that. So I decided to go with DHC where I know the percent. I told Dermalogica that if they had more MAP than DHC and were willing to confirm that in writing, I would immediately switch to them. No word back.

              Also, DHC is much less expensive ($38 for 0.84oz vs. $85 for 0.3oz of Dermalogica).

              DHC is a very established brand in Japan, so I’m not that concerned about quality control. Their site is set up kind of poorly, so it can be hard to find what you’re looking for. Here’s the link to the Vitamin C Essence:


              I also got the CoQ10 lotion. It’s thin, more like a toner. They have a lot of CoQ10 products, but based on the ingredient list, this seems to be the only one that actually has a meaningful amount of CoQ10. For that matter, it’s the only product I’ve found anywhere that seems to have a meaningful amount of CoQ10 other than the Lancer one at Nordstrom. And it’s only $10 for the small size. But it’s kind of sticky–watery yet sticky–so I’m not sure if I’ll be buying it again.

              John, is there a pH I should stick with for MAP? Like, if I’m mixing it in with other stuff to put on my face, should I make sure the other stuff is of a certain pH? Thanks so much for your very informative site!

              Posted by INMM | May 6, 2013, 10:52 pm
              • Ooh thanks for chiming in with your experience! Lol @ tasting it. 😉 It actually does contain water (and a lot of it); the other ingredients just make it seem different.

                And I agree with you that I’d definitely recommend the DHC over the Dermalogica due to the known % of MAP versus the unknown. However, even if it does contain 15% MAP, the price is ridiculous. At that point, even the most expensive L-ascorbic acid products are better than this product in terms of price AND quality; though many expensive L-AA products aren’t that great themselves, either.

                However, when it comes to the CoQ10 lotion, I disagree in terms of the claim that it has “meaningful” amounts of CoQ10. Based on the ingredients list, CoQ10 comes after phenoxyethanol (the preservative). Since that ingredient is hardly ever used above 1.0%, it would appear that there is even less CoQ10. There are other products out there with more CoQ10, though that antioxidant certainly isn’t that great when it comes to topical skin care anyways, at least not enough to look for a stand-alone CoQ10 product.

                As for the pH issue with MAP, there really isn’t one that has much relevance to topical skin care. In an aqueous solution alone, MAP gives a slightly basic pH. However, when used in skin care products, it is usually neutralized with a pH adjuster such as citric acid. The lower of the overall pH doesn’t meaningfully reduce efficacy, but may lead to some cloudiness in a product’s color. Still, you can use MAP with most other ingredients.

                Posted by John | May 7, 2013, 6:44 pm
                • Thanks so much for your response!

                  Do you have any idea of what percent or amount of MAP is needed to get the same effects as 15% L-ascorbic acid?

                  I didn’t know that about the CoQ10 lotion. It was mentioned fairly early in the list of ingredients, so I thought it would have a meaningful amount. What about the Lancer product?


                  I’ve read things consistent with your viewpoint that topical CoQ10 isn’t that important for skin. Zoe Diana Draelos, in one of her books, wrote about how CoQ10’s partition coefficient value (logP) of 11 is too large for the molecule to penetrate the skin. To me, this suggests that the benefit of topical CoQ10 would be as a layer of “sunscreen” rather than an internal repair ingredient. I’ve heard that idebenone is similar to CoQ10 but formulated to better get inside the skin. I’ve also heard that it’s irritating, however. Any thoughts on idebenone?

                  Love your site!

                  Posted by INMM | May 7, 2013, 8:06 pm
                  • You’re welcome!

                    I don’t think typical MAP concentrations used in skin care can ever achieve the same effects as 15% L-AA unfortunately. Though of course, MAP is still an option for those who are sensitive and/or unwilling to use L-AA products.

                    The Lancer product MIGHT contain good amounts of CoQ10. But all the other ingredients are either present in the wrong form and/or not present in high enough concentrations. So it’s essentially a one-noted CoQ10 product anyways. Keep in mind that these are all subjective estimations because there’s no way to really know how much of each ingredient is present, without something like a preservative to indicate concentrations, among other things. But for the price, you will encounter similar ingredient lists from Paula’s Choice for example. I personally wouldn’t recommend the LANCER product.

                    As for the partition coefficient, that doesn’t actually refer to the size of the molecule. It refers to its solubility and therefore, its ability to penetrate into the skin. That number is a useful tool when it comes to evaluating an ingredient’s topical efficacy. However, it’s only a general guideline that’s not to be taken at face value. If you read that book, you will also note that vitamin E has a LogP of 10. But clearly, that ingredient is effective at penetrating the skin.

                    Finally, as for idebenone, I believe it is a more efficient and “better” overall antioxidant than CoQ10. But it isn’t necessarily very photoprotective, and should not be used in place of other more demonstrated ones like vitamins C, E, and several polyphenolic ones.

                    Anyways, thanks for the support and enthusiasm!

                    Posted by John | May 7, 2013, 10:37 pm
  3. Hi John, I have a question about glycolic acid. I use Jan Marini Bioglycolic Facial Cleanser, which has glycolic acid, in the morning. I put it on my dry face and leave it on for 5 minutes and then rinse off. The problem is that my skin is extremely oily. When I wake up I pretty much have an oil slick on my face. If I apply the glycolic face wash to my oily face and let it sit for 5 minutes, will it be able to do its magic despite the large amount of oil on my face? Thanks!

    Posted by Vanessa | February 26, 2013, 8:51 pm
    • Well, the detergent content in most cleansers will fluidize the oil on your face, allowing some penetration of ingredients. Still I’d recommend at least splashing your face with water, pat dry, and then put on the cleanser. But as long as you’re seeing results with that product, you should be fine.

      IUltimately, would prefer if you used a leave-on glycolic acid product, but that’s up to you.

      Posted by John | February 28, 2013, 4:22 pm

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