What is the ingredient lactic acid?

November 13, 2025 •

4 min read

Lactic acid, a naturally occurring alpha-hydroxy acid, was first isolated from sour milk in 1780. Today, this multipurpose ingredient is widely used in both the skincare and food industries for its unique properties as an exfoliant, humectant, and preservative.

Quick Summary

A guide to the ingredient lactic acid, covering its functions as a gentle AHA in skincare and a preservative in foods. Explores its origins, skin benefits, food applications, and production methods.

Key Points

Exfoliates and Hydrates: Lactic acid is a gentle alpha-hydroxy acid (AHA) that removes dead skin cells while acting as a humectant to retain moisture.
Suitable for Sensitive Skin: Its larger molecular size leads to slower penetration, making it less irritating than other AHAs like glycolic acid and ideal for dry or sensitive skin.
Common in Food Preservation: Used as an antimicrobial agent and pH regulator in food manufacturing to extend shelf life in products like yogurt, sourdough, and pickled goods.
Typically Vegan-Friendly: Despite its name derived from milk, most modern commercial lactic acid is produced via plant-based fermentation, but always verify the source if following a strict vegan diet.
Improves Tone and Texture: In skincare, it helps fade dark spots, smooth fine lines, and promotes an even, radiant complexion over time.
Increases Sun Sensitivity: Like all AHAs, it increases the skin's vulnerability to UV damage, so daily sunscreen use is essential, especially with topical application.

What Exactly is the Ingredient Lactic Acid?

Lactic acid is an organic compound with the chemical formula $C_3H_6O_3$. As a type of alpha-hydroxy acid (AHA), it functions by loosening the bonds that hold together dead skin cells, promoting gentle exfoliation and accelerated cell turnover. While it was historically discovered in dairy, modern commercial production typically involves the fermentation of plant-based carbohydrates like corn starch or beets by lactic acid bacteria (LAB). This process is crucial because it allows for scalable and vegan-friendly production that meets high industry standards for consistency and safety. In its raw form, lactic acid is a colorless liquid or white powder that is odorless and hygroscopic.

Lactic Acid in Skincare: How It Benefits Your Complexion

Lactic acid is celebrated in the skincare world for its effectiveness, particularly for those with sensitive or dry skin, because of its larger molecular size compared to AHAs like glycolic acid. This means it doesn't penetrate as deeply, leading to a slower, gentler exfoliation with less potential for irritation. Lactic acid offers a range of skin benefits:

Gentle Exfoliation: It effectively sloughs off dead skin cells on the surface, revealing a fresher, smoother, and brighter complexion underneath.
Hydration: Uniquely, lactic acid acts as a humectant, helping to attract and bind moisture to the skin. This improves the skin's natural moisturizing factor (NMF), making it an excellent choice for dry or dehydrated skin types.
Improved Tone and Texture: By promoting cellular renewal, it helps to even out skin tone, reduce the appearance of dark spots, and smooth rough patches.
Anti-Aging Effects: Regular use can stimulate collagen production, which helps to reduce the appearance of fine lines and wrinkles over time, leading to firmer, plumper skin.
Acne Management: Its exfoliating and antimicrobial properties help to decongest pores and keep acne-causing bacteria at bay, making it suitable for managing breakouts.

How to Use Lactic Acid Products

To incorporate lactic acid into your skincare routine, consider these tips:

Start Low and Slow: Begin with a product containing a lower concentration (e.g., 5%) and use it just a few nights a week to build tolerance.
Nighttime Application: Because AHAs can increase sun sensitivity, it is best to use lactic acid in your evening routine.
Use with Sunscreen: Always wear a broad-spectrum sunscreen with SPF 30 or higher during the day to protect your newly exfoliated skin from UV damage.
Avoid Over-Exfoliation: Do not use lactic acid with other aggressive exfoliants like retinoids or powerful scrubs in the same routine, as this can damage the skin's barrier.

Lactic Acid in the Food Industry: A Taste and Safety Enhancer

In addition to cosmetics, lactic acid (E270) is a crucial ingredient in food processing, valued for its roles in preservation, flavor, and texture. Its applications include:

Flavoring Agent: It imparts a mild, tangy or sour taste found in foods like yogurt, sourdough bread, and pickled vegetables.
Preservative and Antimicrobial Agent: The acidic properties of lactic acid create an environment that inhibits the growth of spoilage bacteria and pathogens, extending the shelf life of products.
Acidity Regulator: It helps control the pH level of foods, which is essential for consistent taste, texture, and stability in items like cheese, soft drinks, and processed meat.
Curing Agent: Used in processed meats like cured fish and deli meats to control bacterial growth and enhance flavor.

Lactic Acid vs. Glycolic Acid: A Comparative Analysis

Both lactic and glycolic acids are popular AHAs, but their differences make them better suited for specific skin types and concerns. The table below highlights the key distinctions:


Feature	Lactic Acid	Glycolic Acid
Molecular Size	Larger molecules	Smaller molecules
Depth of Penetration	Stays on the surface layer	Penetrates deeper into the skin
Primary Function	Gentle exfoliation and hydration	Deeper exfoliation and resurfacing
Skin Type Suitability	Excellent for sensitive, dry, and mature skin	Better for oily, acne-prone, and resilient skin
Hydration Effect	Excellent humectant, increases skin's moisture	Less hydrating, more focused on exfoliation
Irritation Potential	Lower risk of irritation	Higher risk of irritation, especially for beginners
Derived From	Fermented plant sugars (commonly)	Sugarcane

Is Lactic Acid Vegan? Understanding the Sources

The "lac" in lactic acid originates from its historical isolation from sour milk, and while it's a valid concern, most modern lactic acid is vegan. The association with milk is often a point of confusion for vegans and the lactose intolerant. The key takeaway is to check the sourcing. The majority of commercially produced lactic acid used in foods and cosmetics today is created through the bio-fermentation of carbohydrates from plant sources, such as corn or beets. Prominent manufacturers like Corbion and Henan Jindan Lactic Acid Technology specifically use plant-based sugars. As always, checking for a vegan certification or directly contacting the manufacturer for clarification is the only way to be 100% certain.

Conclusion: The Versatile Ingredient Lactic Acid

From giving kimchi its tang to helping fade hyperpigmentation, the ingredient lactic acid is a versatile powerhouse with a long history of beneficial use. Its dual function as a gentle exfoliant and effective humectant makes it a favorite in skincare, especially for those seeking to improve texture and hydration without causing irritation. Meanwhile, its antimicrobial and flavor-enhancing properties secure its place as a staple food additive. While its name might suggest a dairy origin, the vast majority of commercial lactic acid is plant-derived, making it accessible to a wide range of consumers, including those on vegan diets. Always consider your skin type or dietary needs when choosing products containing this fascinating and multifunctional ingredient.

Learn more about lactic acid's applications in food science by consulting trusted resources like the National Institutes of Health (NIH) research database for peer-reviewed studies.

Frequently Asked Questions

Lactic acid exfoliates the skin's surface by breaking down the bonds between dead skin cells, promoting cell turnover for a smoother, brighter complexion. It also functions as a humectant, drawing moisture into the skin to improve hydration and texture.

Yes, lactic acid is generally considered one of the gentlest AHAs due to its larger molecular size, which prevents it from penetrating too deeply. This reduces the risk of irritation, making it a great option for sensitive or dry skin.

Yes, most lactic acid used in food production is vegan. It is typically produced by fermenting plant-based sugars from sources like corn or beets. However, it is wise to check for vegan certification or with the manufacturer to be certain.

When starting, it is best to use lactic acid 2-3 times per week to allow your skin to build tolerance. Many people can eventually use lower concentrations daily, but listen to your skin and reduce frequency if you experience irritation.

Lactic acid has a larger molecular structure and is milder, providing gentler exfoliation and better hydration. Glycolic acid has a smaller molecular structure, penetrates deeper, and is more potent, making it better for stubborn texture and pigmentation but with a higher risk of irritation.

Potential side effects, especially with overuse or for new users, include redness, stinging, dryness, or mild peeling. It is crucial to always use sunscreen, as it increases sun sensitivity.

Yes, lactic acid can help manage acne by exfoliating dead skin cells and preventing clogged pores. Its gentle nature and ability to increase cell turnover can help improve the texture and appearance of acne-prone skin.