If we told you that sour milk was the key to beautiful, bright, healthy skin, would you believe us? Sour milk contains lactic acid, a multi-tasking ingredient that provides numerous benefits to the skin. Lactic acid benefits include skin exfoliation, brightening, reduced acne breakouts, increased skin hydration, anti-aging effects, and more. Fortunately, lactic acid is included in a variety of skin care products (i.e. lactic acid lotion, lactic acid peel, etc.) so that you don’t have to bathe in sour milk like Cleopatra did over 2,000 years ago! In this post, we are going to dive deep into the benefits of lactic acid for skin, how to use lactic acid, and the best skin care products with lactic acid.
If you’re researching lactic acid, you might be looking for clean yet effective skincare. One brand we recommend is Carrot & Stick. We’ve recommended 2 products at the bottom of this article.
What is Lactic Acid?
Lactic acid is an organic compound that is produced both naturally and synthetically. As mentioned above, it is naturally found in sour milk products (i.e. yogurt, kefir, cottage cheese). Raw milk that has not gone sour is sometimes referred to as “sweet milk”, because it contains the sugar lactose. Fermentation converts the lactose to lactic acid, which has a sour flavor, hence sour milk.
With a hydroxyl group adjacent to the carboxyl group, lactic acid is classified as an alpha-hydroxy acid (AHA). AHAs are frequently used in skin care products because they have the ability to exfoliate the skin, stimulate the skin’s natural regeneration process, and help the skin to retain moisture. Other AHAs include glycolic acid, mandelic acid, tartaric acid, malic acid, and citric acid.
What Makes Lactic Acid Unique?
As you can see, there are many AHAs used in skin care, which begs the question, “What makes lactic acid unique?” First is lactic acid’s molecular size. So why should you care about molecular size? Molecular size matters because the smaller a molecule, the more easily it gets into the skin. For example, glycolic acid is the smallest AHA, which means it penetrates the skin better and faster than all of the others. This is why glycolic acid is considered to be the strongest AHA. However, stronger doesn’t always equal better. If you have sensitive skin or you have never used an AHA to exfoliate, glycolic acid may cause skin irritation, redness, and swelling. Thus, lactic acid is best for those with sensitive skin and for those who have never exfoliated with an AHA before. Lactic acid also imparts unique benefits that most of the other AHAs cannot provide, such as boosting hydration, stimulating collagen synthesis, improving skin discoloration, and more.
Top 5 Lactic Acid Benefits
In addition to being an alternative to glycolic acid for those with sensitive skin, lactic acid has been proven to impart numerous benefits when applied to the skin. Below are the top 5 lactic acid benefits for skin.
- Exfoliates + brightens the skin One of the key benefits of lactic acid is its ability to exfoliate and brighten the skin. As per the American Academy of Dermatology, exfoliation is defined as “the process of removing dead skin cells from the outer layer of your skin”. There are two primary forms of exfoliation: mechanical exfoliation and chemical exfoliation. Mechanical exfoliation utilizes an abrasive surface or substance to physically remove dead skin cells, while chemical exfoliation involves using chemical agents to break up dead skin cells, allowing them to be washed away more easily. Lactic acid is considered to be a chemical exfoliant.
Lactic acid works by breaking down keratin, a protein that acts as a glue to hold together the dead skin cells that make up the stratum corneum. By dissolving keratin, lactic acid helps to slough off these dead skin cells, effectively exfoliating the skin. It also enhances cellular renewal by increasing cell turnover rates in the upper layers of your skin. Ultimately, lactic acid leaves the skin looking brighter with a more even tone.
- Prevents acne If you have acne-prone skin, you may want to give lactic acid a try. Blemishes form due to excess sebum, dead skin cells, and bacteria clogging pores, followed by inflammation and swelling. Lactic acid sloughs away the dead skin cells that can clog pores and cause acne breakouts. In addition, its moisturizing effects (more on this below) keep the skin hydrated and soft, allowing blemishes to heal better.
- Boosts skin hydration Chemical exfoliants are typically associated with skin dryness and peeling due to their exfoliating effects. This is not the case with lactic acid. In fact, the opposite is true: lactic acid is a powerful moisturizer. It improves skin hydration by functioning as a humectant. A humectant is a hygroscopic substance that has a molecular structure with several hydrophilic (water loving) groups. This structure allows humectants to attract and retain the moisture in the air nearby via absorption, drawing the water vapor into or beneath the surface. Humectants improve moisture retention and may also help other topical skin care ingredients to perform better. When lactic acid lotion is applied to the body, its exfoliating action helps to break down rough skin while its hydrating action replenishes dry skin.
Lactic acid is also a key element of the skin’s Natural Moisturizing Factor (NMF). The NMF is primarily composed of free amino acids and various derivatives of these amino acids, for example, PCA, urocanic acid, and inorganic salts, sugars, as well as urea and lactic acid. The role of the NMF is to maintain adequate skin hydration. The NMF can become depleted with age and also from routine exposure to sensitizing ingredients like drying cleansing agents and denatured alcohol. This leads to visibly dry, tight-feeling, flaky skin. Thus, by using ingredients that help to replenish NMF, such as lactic acid, the skin will be better hydrated. Ultimately, the skin will look and feel healthy, smooth, and supple.
Lastly, lactic acid increases levels of ceramides, which are lipids naturally produced by the skin and are vital in supporting the skin’s barrier function. Without these essential lipids, the skin barrier is weakened, resulting in symptoms such as dry, itchy, or irritated skin. By stimulating ceramide synthesis, lactic acid helps to prevent transepidermal water loss and promote healthy, intact, moisturized skin.
- Corrects skin discoloration When lactic acid is used in high concentrations, such as with a lactic acid peel, it has the ability to lighten the skin and correct skin discoloration (hyperpigmentation). Specifically, lactic acid has been shown to directly inhibit tyrosinase activity. Tyrosinase is a key enzyme involved in the synthesis of melanin, the pigment that gives skin color and also contributes to the formation of undesirable dark spots. Therefore, by inhibiting tyrosinase, lactic acid may be able to reduce abnormal pigmentation associated with aging and exposure to UV light.
- Helps fight signs of aging Lactic acid has the ability to reduce the appearance of lines, wrinkles, and other signs of aging by stimulating collagen synthesis. Collagen is a structural protein naturally produced by the body that is responsible for keeping skin strong and firm. Collagen production starts to decline around age 25 and continues to decrease with age. Collagen levels also decrease due to factors such as smoking, sugar consumption, and overexposure to the sun’s ultraviolet rays. Ultimately, this decrease leads to wrinkles and sagging skin. Even though many skin care products include collagen as an ingredient, it is simply too large to penetrate the skin deep enough to have an anti-aging effect. This is why using ingredients that can penetrate the skin and stimulate collagen synthesis, such as lactic acid, provide effective anti-aging benefits.
The Best Ways to Use Lactic Acid
After reading all of the lactic acid benefits, you may be wondering how to use lactic acid in your skin care routine. The answer to this question is not black and white, since there are many different types of lactic acid products. Below we’ll describe how to use three different types of products: lactic acid peel, lactic acid lotion, and lactic acid moisturizer.
Try a peel to maximize exfoliation
A lactic acid peel offers a strong concentration of lactic acid to exfoliate the top layers of skin (epidermis). Professional lactic acid peels may also target the middle layers of skin (dermis). Despite the name, your skin doesn’t noticeably “peel” off with a lactic acid peel. The frequency with which you use a lactic acid peel will depend on the strength of the peel, and also how well your skin tolerates acid exfoliation. It is typically recommended to use a lactic acid peel one to two times per week. If you notice skin irritation, rash, or itchiness with a lactic acid peel, you may want to decrease the frequency.
Use a lotion for dry, rough skin
A lactic acid lotion is typically intended to be used on the body, not the face. Most lactic acid lotions are formulated with a low concentration of lactic acid because their primary purpose is to provide moisturization with mild exfoliation. A lactic acid lotion can be applied to dry, rough skin daily.
Add a moisturizer to your nightly skin care routine
A lactic acid moisturizer may refer to a cream or serum. These products are intended to be used on the face and are not as strong as a lactic acid peel. You may want to use a lactic acid moisturizer if you want to increase skin hydration while brightening the skin and reducing signs of aging. You can typically apply a lactic acid moisturizer once daily, usually in the evening.
What strength of lactic acid is best?
When choosing a lactic acid product, you should be looking at the percentage of the acid in the product, as well as the pH level of the formula. Over-the-counter lactic acid products typically range from 5% to 12% concentration, while peels used in a dermatologist’s office will have a much higher concentration of lactic acid. Higher concentrations of lactic acid will penetrate both the epidermis (upper layer of skin) and the dermis (middle layer of skin). As a rule of thumb, the higher the concentration, the stronger the results.
Percentage isn’t the only thing to look at
In addition to the percentage of a lactic acid product, it’s also important to determine the pH. This is because lactic acid works best at a lower (acidic) pH, around 3.5 to 4. If the pH is higher than this range, lactic acid will not exfoliate the skin, however, it will still provide water-binding effects. If the pH is lower than this range, you may experience stinging and redness. Unfortunately, the pH of a formula is almost never listed on packaging. So how can you pick an effective product? Many skin care experts say you should feel a slight tingle for a few seconds after applying a product, and that a truly effective product should cause your skin to look instantly brighter.
How do I know if lactic acid is right for my skin type?
Lactic acid is an effective ingredient for all skin types, even those with sensitive skin. It is particularly beneficial for treating acne, dry skin, and dull skin. However, you should not use a lactic acid product if you have skin irritation, such as redness, swelling, or open sores.
Things you need to know before trying lactic acid
Since lactic acid causes exfoliation of the top layers of skin, you may want to consider discontinuing other exfoliating products (i.e. retinoids, scrubs) when you’re using a lactic acid product to avoid irritation. In addition, the exfoliating effect of lactic acid can cause your skin to become more prone to sun damage. Thus, it is recommended to use a broad spectrum SPF 30 sunscreen daily if you decide to include lactic acid in your skin care regimen.
The best lactic acid products
Carrot & Stick The Brightening Pads
One of the easiest ways to give skin a thorough (but gentle) exfoliation is with pre-soaked pads. The Brightening Pads contain a potent blend of salicylic, lactic and mandelic acids to help sweep away dead skin cells, revealing brighter, smoother looking skin. Herbal extracts fight photo damage and keep redness in check. The pads can be used on the face, neck and décolleté.
Carrot & Stick The Exfoliating Peel
This exfoliating treatment features a blend of alpha-hydroxy acids (glycolic, lactic and pyruvic) to revitalize damaged skin, smoothing the appearance of lines, minimizing the look of pores, and sloughing off dead skin.
References: Wikipedia “Soured Milk”, Indian J Dermatol. 2012 Nov-Dec; 57(6): 444–448, Healthline “Everything You Need to Know About Lactic Acid Peels”