Lactic acid is an ingredient commonly found in many over-the-counter (OTC) cosmetic products. It is also available in stronger concentrations in medical offices. Lactic acid is an antioxidant, a chemical exfoliant, and helps moisturize the skin.

Products containing lactic acid for home use are usually mild, with concentrations of 10% or less. Products containing more than 10–15% require professional application.

This article discusses what lactic acid is, how it affects the skin, and how to use it. It also examines the potential risks and side effects.

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Lactic acid is one of the most common types of alpha-hydroxy acid (AHA) used in cosmetic products. AHAs are present in OTC chemical exfoliants and professional chemical peels.

The Vegetarian Resource Group (VRG) notes that most lactic acid is produced by a fermentation process using cornstarch or beet sugar, meaning that some products containing lactic acid may be suitable for vegans.

Fermenting milk products can also produce lactic acid.

Other types of AHAs include:

  • glycolic acid, which comes from sugar cane
  • citric acid, which derives from citrus fruits
  • malic acid, which comes from apples
  • tartaric acid, which derives from grapes

How it affects the skin

Chemical peels that contain AHAs, such as lactic acid, remove the top layer of dead skin cells. Typically, superficial chemical peels contain a lactic acid concentration of 10–30%.

Although they are called peels, the skin does not noticeably peel off. Instead, the dead skin cells come away from the top layer of the skin when people cleanse their face in the morning after using chemical peels.

According to the Food & Drug Administration (FDA), some of the potential benefits of using lactic acid on the skin include:

  • improving skin texture and tone
  • improving skin appearance or firmness
  • reducing dark spots
  • smoothing fine lines and surface wrinkles
  • unblocking and cleansing pores

Lactic acid is a versatile ingredient present in various skin care products. These include:

  • body scrubs
  • cleansers
  • essences
  • exfoliators
  • facial treatments
  • serums
  • toners

Depending on the specific product and its place in a person’s skin care regime, the instructions for use will differ. It is important to follow these instructions carefully to ensure the best outcome.

Lactic acid, alongside other AHAs, increases the skin’s sensitivity to the sun. As a result, people should always wear sunscreen if they incorporate an AHA into their skin care routine.

Performing a patch test

The higher the concentration of lactic acid, the more likely it is that the product will irritate a person’s skin. People should always conduct a patch test and begin with a lower concentration before moving to stronger products.

The American Academy of Dermatology Association (AAD) suggests that a person tests the skin care products by:

  1. Applying the product to a test spot, such as the bend of the elbow or the underside of the arm. People should do this twice a day for 7–10 days, using the same amount and thickness they would be using if they were applying the product normally.
  2. Leaving the product on for as long as the packet instructions suggest.
  3. Using the product if no irritation or inflammation occurs.

The AAD notes that some ingredients such as glycolic acid will normally cause temporary irritation, particularly if a person has sensitive skin. As with lactic acid, glycolic acid is an AHA.

What to check for in products

The FDA requires an ingredient declaration on all cosmetic products sold to end users.

Milder peels that a person can use at home will contain lactic acid concentrations of 10% or less.

People should check that lactic acid is one of the first ingredients on the list. The product may not contain enough lactic acid to benefit the skin if it appears toward the end.

Some people may want to consider visiting a professional for a chemical peel. Typically this will be for a stronger formulation or more visible and immediate results.

There are three levels of dermatologist-provided chemical peels:

  • Refreshing or lunchtime peels: These take 1–7 days to heal. People may require 3–5 visits, and a person can repeat this treatment every 2–5 weeks.
  • Medium peels: These take 7–14 days to heal. A person will also require a follow-up appointment.
  • Deep peels: These can take 14–21 days to heal. A person will need to return to the dermatologist the next day and have several follow-up visits.

People can only ever have one deep peel, but repeat medium and mild peels when necessary. A person should speak with their dermatologist to determine the best treatment plan for them.

According to a 2018 article, medium chemical peels usually consist of 35–50% trichloracetic acid (TCA) and 70% glycolic acid.

The dermatologist may pretreat the skin using Jessner’s solution. Jessner’s solution contains:

  • resorcinol
  • salicylic acid
  • lactic acid
  • ethanol lactic acid

Deeper peels often use phenol peels that consist of croton oil, phenol, and water for dilution.

The FDA states that products containing lactic acid are safe to use, providing the product:

  • has a concentration of 10% or less
  • has a pH of 3.5 or more
  • is either formulated so that it protects the skin from sun sensitivity or instructs the users to use daily sun protection

It is particularly important that people wear sunscreen when using lactic acid on their skin. This is because the acids can cause the skin to be more susceptible to sun damage.

Depending on the lactic acid concentration, the pH of the product, and how long a person has exposure to the product, people may experience:

If people experience side effects, they should contact a doctor or dermatologist.

People should also avoid using lactic acid on the same days that they incorporate retinol into their skin care routine. People should instead alternate between the two products.

After using lactic acid peels, a person may experience:

  • inflammation
  • mild swelling
  • mild discomfort
  • peeling or flaking skin

After a medium or deep peel, people can expect:

  • skin inflammation
  • swelling
  • blisters
  • skin crusting

A dermatologist will provide details on caring for the skin following these procedures.

Where lactic acid is an AHA, there is also a class of products called beta hydroxy acids (BHAs). Currently, the most commonly used BHA in cosmetics is salicylic acid.

It works similarly to lactic acid, appears to have a lower chance of irritating the skin compared to AHAs. People may use salicylic acid to treat acne.

Learn more about salicylic acid for acne.

OTC products may contain concentration levels of less than 2%. Any products containing more than that require a professional to administer the treatment.

According to the FDA, salicylic acid is not a true BHA. However, cosmetic companies often refer to it as a BHA, leading people to think of it as one.

Learn more about the differences between AHA and BHA for skin care.

A person can try the following skin care products that contain lactic acid:

Please note that the writer of this article has not tried these products. All information presented is purely research-based and correct at the time of publication.

Medical News Today follows a strict product selection and vetting process. Learn more here.

The following are answers to some common questions about lactic acid.

Is lactic acid safe to use in pregnancy?

AHA treatments are safe to use during pregnancy. However, a person should speak with a dermatologist before undergoing treatments if they are pregnant.

Is lactic acid safe to use alongside other anti-aging products?

People can alternate using products containing lactic acid with other anti-aging products, such as vitamin C and retinoid creams.

How long does lactic acid take to work?

The length of time it takes lactic acid to work depends on the product and the intensity of the chemical peel.

DermNet NZ states that AHA peels can take a few months to work.

The AAD states that after a professional chemical peel, a person will notice results once the skin has healed. This can take between 1 day or 14 days, depending on the intensity of the chemical peel.

If a person has undergone a refreshing peel, they may require 3–5 sessions.

Lactic acid is a type of AHA present in many exfoliating skin care products. It removes the top layer of the dead skin cells and can help improve skin texture, reduce dark spots, smooth fine lines, and cleanse pores.

A person can find OTC products containing lactic acid or visit a dermatologist to undergo facial chemical peels containing stronger concentrations.

Side effects can include skin irritation and increased sensitivity to the sun. Before using the product, people should perform a patch test and apply daily sun protection when using products containing lactic acid.