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GUIDE: Why you should use acids in your skincare routine

Header The Moisturizer - GUIDE: Why you should use acids

Hello! How is it going? Today I’m back an informative post about some of the questions that I receive more often. In this case I’m going to talk about acids, those products about which I sometimes speak so normally and that can be unknown for many. Normally I speak of some particular acid (as in this post, in which I told you about glycolic acid), but today I want to give you a more global introduction to know what you can find and know which is best for your skin type, when it is best to use them and with how often you should use them. Do you want to learn a little more about this topic? Here we go!


In this post I’m going to talk about these topics:

1. What are acids?

2. Types of acids. What acids are better for your skin type?

    • Hyaluronic acid.
    • Alpha-lipoic acid.
    • Salicylic acid (BHA or Beta Hydroxy acids).
    • Alpha Hydroxy acids (AHA).

3. When can you use acids?

4. How often can you use acids?    




For many, when I speak of acids, you will have in mind those images of Hollywood films in which a droplet of sulfuric acid melted a whole wall. Fortunately, we will not talk about those acids, but others that bring great benefits to your skin, giving you an incredible look effortlessly. 

Simplifying a lot, an acid is that product with a pH (hydrogen ions concentration) lower than 7 (which is the pH of the water). Usually it is said that our skin is slightly acidic, because it has a pH that oscillates between 4.5 and 5.9. You see that this definition of acid is very broad, since coffee or milk could be considered acidic products, because they usually have a pH lower than the water. Of course, we will go a little further, and we will focus on those acids that are usually used in cosmetics and we can find in the products we use on our daily routines: glycolic acid, salicylic acid, hyaluronic acid, etc. 

Of course, all this could not be that simple, and there is another value of acids that normally tends to be left aside, despite being as important as its pH when considering its efficacy, and it’s the pKa. The pKa (dissociation constant) of an acid is a value that never changes for that particular acid (for example, the pKa of glycolic acid is 3.83). Why are is this relevant to you? Because each brand formulates its products making with a higher or lower pH, thus getting more or less effectiveness. This is not to say that we should look for products with a low pH, since those should only be used by professionals, but we can compare the different products of the market to find those that best suit us. 

After taking you back to your chemistry classes, we now return to the topic we are interested in: acids and their use in cosmetics. Each time we find more products formulated with acids to help you balance your skin tone, exfoliate, reduce acne, etc. However, it can be difficult to understand what each one is for, so in this post I will help you to know them better so you know how they can help you.




Now that you know what acids are, it’s time to get to know a little bit better what you can normally find in your products. In addition, you will be able to see which ones work best with each type of skin and what results each one contributes.   


  • Hyaluronic acid. 

Hyaluronic acid (with a pKa of 2.87) is a little special. It is different from the rest of acids that I’m going to talk about, but as it is one of the most common ones in cosmetics products, I think it is interesting to analyze it in the first place. Hyaluronic acid is naturally found in our skin, and is able to withstand up to 1000 times its weight in water, making it a magnificent component to attract water and hydrate your skin in depth. This is why many products include it, because as we use it we can get a firmer and hydrated skin, reducing wrinkles and fine lines. If you want a good serum with Hyaluronic acid I recommend The Ordinary Hyaluronic acid 2% + B5, which I already told you about before, and that you can get at DECIEM (UK), at Beauty Bay (UK), on Mankind (US & Canada), and The Hut (US & Canada), a great solution to moisturize your skin on the surface and in depth and that works great with any type of skin. You might also want to take a look at the serum The Ordinary Marine Hyaluronics and the Matrixyl 10% + HA, which you can get at DECIEM (UK), at Beauty Bay (UK), on Mankind (US & Canada) and The Hut (US & Canada)  


  • Alpha-Lipoic Acid (ALA).

This acid (with a pKa of 4.52) is a very strong antioxidant that helps rebalance the skin tone and texture, also reducing fine lines and wrinkles. In addition, it is a very soft chemical exfoliator, so you will get a much younger look when using it. It’s designed for all kinds of skins. This acid is very sensitive to sunlight, and the products with higher concentrations of it can make your skin more photosensitive, so you should only use this product in your night routines (and always wear sunscreen, of course). If you want to start using alpha-lipoic acid I recommend you do it with the booster The Ordinary Alpha Lipoic Acid 5%, which you can get at DECIEM (UK), at Beauty Bay (UK) and Mankind (US & Canada)  


  • Salicylic acid (BHA or Beta Hydroxy acids). 

Salicylic acid (with a pKa of 2.97) is an oil-soluble BHA (unlike their cousins, the AHAs, which I’ll talk about below). It works better on oily and combination skin. When applied, it is possible to remove the dead cells that remain on the surface of the skin at the same time that it manages to clean the pores in an effective way. This acid is also known for its soothing properties, in addition to softening the texture, balancing the tone, reducing wrinkles and fine lines and moisturizing. If you are looking for a good exfoliant with salicylic acid I recommend you to try the cleanser ByWishtrend acid-Duo 2% Mild Gel Cleanser, which you can get at Wishtrend, the toner COSRX BHA Skin Returning A-Sol, which you can get at Wishtrend and Mankind (US & Canada), and the booster The Ordinary Salicylic acid 2% Solution, which you can get at DECIEM (UK).


  • Alpha Hydroxy Acids (AHA).

The Alpha Hydroxy acids or AHAs (about which I spoke a little bit in this post) are a set of water soluble acids used as chemical exfoliators, removing dead cells to give you a glowy look. Over the years, the skin takes longer to remove that layer of dead cells, so this type of exfoliation is a great solution to help you keep a younger look, showing your new skin. In general, they work better for normal and dry skin. Within this category we can find different acids, providing each one different results, so after reading this post you can find what is the best acid you will come according to your skin type. If you want to start using the AHAs, I recommend you to start with the mask  The Ordinary AHA 30% + BHA 2% Peeling Solution, which you can get at DECIEM (UK) and Beauty Bay (UK).


a) Glycolic acid. 

Glycolic acid (with a pKa of 3.83) is now one of the best known ones in the market. It is recommended for all of skin types, except the sensitive ones. It is the AHA with the lowest molecular weight, so it penetrates better in the skin than the others. In addition to removing dead skin cells, it also helps reduce acne scars and hyperpigmentation while stimulating collagen production so you have a firmer, more elastic skin. You should keep in mind that this acid is especially photosensitizing, so you should use it exclusively in your night routines (although, of course, in your morning routine you always have to use sunscreen). If you want to start testing glycolic acid, I recommend you do it with the Pixi Glow Tonic (which I spoke about in this post) or The Ordinary Glycolic Acid 7% Toning Solution (about which I spoke a little more in this other post and that you can get at DECIEM (UK), at Beauty Bay (UK), Mankind (US & Canada), and The Hut (US & Canada).  


b) Lactic acid.

Lactic acid (with a pKa of 3.86) works best when it comes to reducing wrinkles and fine lines and balancing the texture of the skin. It is especially recommended for dry skin, although it can also be used without any problem with sensitive skin. As with glycolic acid, lactic acid is best used at night to avoid excessive photosensitizing of the skin. If you want to try the lactic acid I recommend you to start with The Ordinary Lactic Acid 10% + HA 2%, which you can get at DECIEM (UK), at Beauty Bay (UK), at Mankind (US & Canada), and The Hut (US & Canada).  


c) Mandelic acid.

Mandelic acid (with a pKa of 3.41) is another member of the AHAs family. Among its main properties there are reducing fine lines and hyperpigmentation, as well as helping to rebalance the levels of skin oil, making it ideal for oily and sensitive skins. By penetrating the skin less than other acids, it is less potent, but that lower aggressiveness is what makes it a good choice for those who have sensitive skin. If you want to start using mandelic acid I would recommend using the ByWishtrend Mandelic Acid 5% Skin Prep Water Tonic, which you can get at Wishtrend, or the booster The Ordinary Mandelic Acid 10% + HA, which you can get at DECIEM (UK), at Beauty Bay (UK) and Mankind (US & Canada).  


d) Malic acid.

Malic acid (with a pKa of 3.51) has as main functions to preserve the hydration of the skin, to reduce wrinkles and fine lines and to reduce the excessive oil of the skin. It is recommended to use it for all skin types, except for sensitive skin. This acid, which we can find in several fruits (especially in apples), is very common in cosmetics, but if you want to start using I would recommend you do it with the toner COSRX AHA 7 Witehead Power Liquid, which you can get at Wishtrend and at Mankind (US & Canada) or the serum Paula’s Choice Resist Advanced Smoothing Treatment 10% AHA, which you can get at The Hut (US & Canada) and at Mankind (US & Canada).


e) Azelaic acid.

Azelaic acid (with a pKa of 4.55) is a superb tool for combating excess oil and acne, eliminating the damaging bacteria that settle on our skin and reducing inflammation and hyperpigmentation, making it a super solution. It’s best for those with oily skin. Its use is not recommended for those with sensitive skin, as it may cause irritation. If you want to start using azelaic acid in your routines, I would recommend you to try the booster The Ordinary Azelaic Acid Suspension 10%, which you can get at DECIEM (UK) and Beauty Bay (UK).


f) Ascorbic acid.

Ascorbic acid (with a pKa of 4.7), as I have already told you in this post is, currently, one of the most popular acids in cosmetics. Many brands have chosen to develop product lines with vitamin C for its enormous antioxidant properties and its ability to rebalance the tone of the skin. This acid works best on oily, combination and dry skin. Products containing a high amount of ascorbic acid are not recommended for those with sensitive skin, as they may cause irritation. If you want to start using ascorbic acid I recommend you do it with the serum Klairs Freshly Juiced Vitamin Drop, which you can get at Wishtrend and Mankind (US & Canada), the booster The Ordinary Vitamin C Suspension 23% + HA Spheres 2%, which you can get at DECIEM (UK), at Beauty Bay (UK), at Mankind (US & Canada), and The Hut (US & Canada); or the booster The Ordinary Magnesium Ascorbyl Phosphate 10%, which you can get at DECIEM (UK), at Beauty Bay (UK), at Mankind (US & Canada), and The Hut (US & Canada).  




Now that you know a little better the family of acids (which, as you have seen, is quite broad), it is time to know when is the best time to use them. Generally speaking, most acids turn the skin more photosensitive (and therefore radiation from the sun can damage it more easily). That’s why, in general, it’s best to apply them in your night routines, because you won’t run any kind of risk. Of course, there are exceptions, as with hyaluronic acid (which we already saw is a little special), which does not make the skin more photosensitive and can be used without problem in your morning routines. As a general rule, the best time of the year to treat your skin in depth with acids is the winter, because then the solar radiation is lower and you run less risk of damaging your skin. This is not to say that in summer you can not use them, but you will have to do much less often and much more careful. Of course, sunscreen is a fundamental part of your routines and, if you use acids, you should be even more thorough when using it.    




It is difficult to answer this question in generic way, since each acid has its particularities. If you want to start adding acids to your routines, the ideal would be to try once a week and see what results you get, if you notice any kind of irritation or stinging, etc. If all goes well, you will be able to increase the frequency very progressively, going twice a week for a time, then to three times a week, and so on until you can use them daily.  It is important to mention that you should not begin to combine acids to the crazy, as there are some who see their effects enhanced by combining with others, but in certain cases you will get a less effective effect. If you want to start using acids you should start with one, and when it is fully incorporated into your routines, you can add another and see how they work, if you see any detrimental side effects, etc. If you don’t go little by little, you will most likely stress your skin and end up getting irritated, which will get you even worse off how you started.    



I know this has been a little difficult post, but I hope it serves as a guide to know acids a little better and see which can give you the result you seek. If you have any questions do not hesitate to leave me a comment and I will reply as soon as possible.  


If you liked this post and want to continue learning about beauty, cosmetics and skin care I recommend you take a look at these posts:


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