Lactic Acid

Lactic acid is the mildest alpha-hydroxy acid and is commonly used for skin rejuvenation. Apart from its excellent moisturizing effect, it also reduces skin pigmentation and can be used to treat melasma and improve eye bags.

Effects


Grade Level of Evidence
A Multiple double-blind, controlled clinical trials.
B 1 double-blind, controlled clinical trial.
C At least 1 controlled or comparative clinical trial.
D Uncontrolled, observational, animal or in-vitro studies only.
Grade Effect Size of Effect Comments

B

Increased skin hydration

Strong

Effectively resists xerosis by improving the lipid barrier of the skin.

B

Smoother skin

Moderate

8% and 12% lactic acid induces clinical improvement in the roughness of the skin.

B

Skin lightening

Mild

Helps whiten skin, reduce hyperpigmentation and lighten age spots.

C

Wrinkle treatment

Moderate

Improves fine lines and wrinkles, but not deep wrinkles.

C

Melasma treatment

Moderate

Markedly improves melasma severity and area when used at full-strength.

D

Enhanced barrier function

Moderate

Improves the skin barrier by stimulating the production of stratum corneum ceramides.

D

Acne treatment

Moderate

Helps clear acne lesions when used with oral antibiotics or as chemical peels at full-strength.

D

Less visible scars

Mild

Chemical peeling with full-strength lactic acid lightens acne scars after 4 peels.

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Scientific Research


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Table of contents:

1. Sources

Lactic acid is a mild α-hydroxy acid formed through fermentation by lactic acid bacteria. It is found in many foodstuffs, such as sour milk and tomato juice.[1] In animals, it is constantly produced during metabolism and exercise.[2]

2. Bioavailability

The skin permeation of lactic acid depends on its concentration and the pH of the vehicle. In one study using gel formulations, the permeation increased as the concentration of lactic acid rose, and decreased as the pH of gels was increased. The greatest permeation was obtained with a concentration of 9% and a pH of 2.8.[3]

3. Effects on the skin

3.1 Reduced dryness

There is ample evidence that lactic acid helps improve abnormally dry skin, or xerosis. 12% lactic acid lotion has been shown to reduce xerosis severity more effectively than an emollient lotion without lactic acid, as well as a petrolatum-based cream.[4][5]

Furthermore, moisturizers containing lactic acid and urea have been demonstrated to be an appropriate treatment option for xerosis of the foot, including in patients with diabetes.[6][7]

Ammonium lactate, the salt of lactic acid formed by neutralization with ammonium hydroxide, is also effective in treating xerosis. Comparative studies have shown that 12% ammonium lactate lotion is more efficacious than 5% lactic acid lotion,[8] but that 10% lactic acid (Lactinol) was as effective as 12% ammonium lactate (Lac-Hydrin) in reducing the severity of xerosis.[9]

12% ammonium lactate cream is also as effective as pure lanolin, a 5% salicyclic acid and 10% urea ointment (Kerasal) and a liposome-based moisturizing lotion in treating xerosis of the foot.[10][11][12]

In another study, a formulation containing 12% ammonium lactate and 1% pramoxine hydrochloride was found to not only improve skin dryness but also pruritus (itchiness).[13]

Lactic acid provides effective resistance against xerosis by stimulating the synthesis of ceramides, leading to increased stratum corneum ceramide levels, resulting in a superior lipid barrier.[14] It is also a humectant, and prevents transepidermal water loss by attracting water to the stratum corneum.[4]

3.2 Lightening effect

Lactic acid by itself may or may not possess significant skin lightening effects, but appears to be effective when combined with other actives.

One study demonstrated that prolonged treatment with 8.8% lactic acid did not affect skin pigmentation, but lactic acid supplemented with 1% ascorbic acid produced a general whitening effect and modestly lightened age spots after 3 months.[15]

A double-blind, vehicle controlled trial however found that topical 8% lactic acid cream significantly improved mottled hyperpigmentation and sallowness on the forearms after 22 weeks of treatment.[16]

Chemical peeling using a combination of 15% lactic acid and 3.75% trichloroacetic acid also significantly improved dark circles under the eyes in almost all patients in a third study.[17]

Presumably, the exfoliative action of lactic acid may contribute to its whitening effect on the skin. Since much of the melanin in the skin surface resides in epithelial cells, it is possible that lactic acid reduces pigmentation because it speeds the transit of epithelial cells from the lower epidermis to the surface.[15]

3.3 Anti-wrinkle effect

A few studies have investigated the effects of topical lactic acid on wrinkles and fine lines. An early study found that 12% lactic acid applied twice a day for 3 months, clinically improved the appearance of fine lines and wrinkles by 45% after 16 weeks, while 5% lactic acid led to an improvement of 20%.[18] More recently, a chemical peel formulation containing 85% lactic acid significantly reduced fine wrinkles on the outer lateral region of the left eye after 2 peels, and on the outer lateral region of the right eye after 3 peels.[1]

Lactic acid peels do not improve deep wrinkles however.[1] As superficial peeling reaches the epidermis, it is more effective on fine wrinkles.[19]

3.4 Smoothing effect

Treatment with 8% lactic acid has been shown to reduce roughness on the forearms in a double-blind, vehicle-controlled trial.[16] Similarly, 12% lactic applied twice daily for 3 months, led to clinical improvement in skin smoothness.[18]

3.5 Improved barrier function

Lactic acid, particularly the L isomer, has been shown to raise ceramide biosynthesis, leading to increased cermamide levels in the stratum corneum and hence an improved lipid barrier of the skin.[14]

Experiments on mice also indicate that 5% lactic acid induced enhanced desquamation and increased the number and secretion of lamellar bodies, thereby improving the skin barrier without increasing transepidermal water loss,[20] whereas 12% lactic acid increased epidermal and dermal firmness and thickness.[18]

3.6 Melasma treatment

In one study, pure (92%) lactic acid at full-strength used as a peeling agent every 3 weeks, markedly improvement melasma severity in less than 6 sessions.[21] A later study by the same authors found that this was as effective as Jessner's solution in treating melasma.[22]

A series of 3 case studies also showed that treatment with a superficial chemical peel containing a blend of resorcinol, lactic acid, salicylic acid, and retinol, combined with a topical multimodal skin brightener as postpeel maintenance therapy can be an effective approach for managing moderate to severe melasma.[23]

3.7 Acne treatment

Lactic acid may be useful in treating acne when combined with oral antibiotics. In an open clinical study, a 5% aqueous solution of lactic acid applied twice daily to the face, combined with oral antibiotics given for 4-week periods whenever acne severity was high, reduced inflammatory lesions and comedones by 50% to 100% in the majority of patients within 30 weeks.[24]

Full strength, 92% lactic acid used as chemical peels at an interval of 2 weeks, have also been shown to help clear acne lesions and improve superficial acne scarring in less than 4 sessions.[25]

4. Side Effects

4.1 Adverse skin reactions

Lactic acid is generally well-tolerated, though this naturally depends on the concentration of acid used in the formulation.

92% lactic acid at full-strength appeared to cause significant dropout rates in studies of their effectiveness in melasma treatment, although the reasons for these dropouts were not explained.[21][22]

Nevertheless, lower concentrations of lactic acid lead to only mild and temporary side effects on the skin, including erythema, edema, dryness, telangiectasias and a pricking sensation.[17][24]

Encapsulating lactic acid in the inner water phase of an emulsion seems to help reduce adverse skin reactions. A water-in-oil emulsion of lactic acid has been shown to induce less stinging than an oil-in-water emulsion. Increasing the mineral oil content of an oil-in-water emulsion also tends to decrease the stinging potential of the formulation.[26]

Scientific References


  1. Prestes PS, de Oliveira MM, Leonardi GR. Randomized clinical efficacy of superficial peeling with 85% lactic acid versus 70% glycolic acid. An Bras Dermatol. (2013)
  2. Robergs RA, Ghiasvand F, Parker D. Biochemistry of exercise-induced metabolic acidosis. Am J Physiol Regul Integr Comp Physiol. (2004)
  3. Sourla DE, et. al. Optimization of in vitro skin permeation by lactic acid from gel formulations. J Cosmet Sci. (2003)
  4. Dahl MV, Dahl AC. 12% lactate lotion for the treatment of xerosis. A double-blind clinical evaluation. Arch Dermatol. (1983)
  5. Wehr R, et. al. A controlled two-center study of lactate 12 percent lotion and a petrolatum-based creme in patients with xerosis. Cutis. (1986)
  6. Grossman AB. Clinical evaluation of 35% urea in a water-lipid-based foam containing lactic acid for treatment of mild-to-moderate xerosis of the foot. J Am Podiatr Med Assoc. (2011)
  7. Pham HT, et. al. A prospective, randomized, controlled double-blind study of a moisturizer for xerosis of the feet in patients with diabetes. Ostomy Wound Manage. (2002)
  8. Rogers RS 3rd, et. al. Comparative efficacy of 12% ammonium lactate lotion and 5% lactic acid lotion in the treatment of moderate to severe xerosis. J Am Acad Dermatol. (1989)
  9. Jennings MB, et. al. A comparative study of lactic acid 10% and ammonium lactate 12% lotion in the treatment of foot xerosis. J Am Podiatr Med Assoc. (2002)
  10. Jennings MB, et. al. A double-blind clinical trial comparing the efficacy and safety of pure lanolin versus ammonium lactate 12% cream for the treatment of moderate to severe foot xerosis. Cutis. (2003)
  11. Jennings MB, et. al. Comparison of salicylic acid and urea versus ammonium lactate for the treatment of foot xerosis. A randomized, double-blind, clinical study. J Am Podiatr Med Assoc. (1998)
  12. Uy JJ, et. al. Ammonium lactate 12% lotion versus a liposome-based moisturizing lotion for plantar xerosis. A double-blind comparison study. J Am Podiatr Med Assoc. (1999)
  13. Grove G, Zerweck C. An evaluation of the moisturizing and anti-itch effects of a lactic acid and pramoxine hydrochloride cream. Cutis. (2004)
  14. Rawlings AV, et. al. Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function. Arch Dermatol Res. (1996)
  15. Smith WP. The effects of topical l(+) lactic Acid and ascorbic Acid on skin whitening. Int J Cosmet Sci. (1999)
  16. Stiller MJ, et. al. Topical 8% glycolic acid and 8% L-lactic acid creams for the treatment of photodamaged skin. A double-blind vehicle-controlled clinical trial. Arch Dermatol. (1996)
  17. Vavouli C, et. al. Chemical peeling with trichloroacetic acid and lactic acid for infraorbital dark circles. J Cosmet Dermatol. (2013)
  18. Smith WP. Epidermal and dermal effects of topical lactic acid. J Am Acad Dermatol. (1996)
  19. Clark E, Scerri L. Superficial and medium-depth chemical peels. Clin Dermatol. (2008)
  20. Kim TH, et. al. The effects of topical alpha-hydroxyacids on the normal skin barrier of hairless mice. Br J Dermatol. (2001)
  21. Sharquie KE, et. al. Lactic acid as a new therapeutic peeling agent in melasma. Dermatol Surg. (2005)
  22. Sharquie KE, Al-Tikreety MM, Al-Mashhadani SA. Lactic acid chemical peels as a new therapeutic modality in melasma in comparison to Jessner's solution chemical peels. Dermatol Surg. (2006)
  23. Goberdhan LT, et. al. Assessment of a superficial chemical peel combined with a multimodal, hydroquinone-free skin brightener using in vivo reflectance confocal microscopy. J Drugs Dermatol. (2013)
  24. Garg T, et. al. Long term topical application of lactic acid/lactate lotion as a preventive treatment for acne vulgaris. Indian J Dermatol Venereol Leprol. (2002)
  25. Sachdeva S. Lactic acid peeling in superficial acne scarring in Indian skin. J Cosmet Dermatol. (2010)
  26. Sahlin A, Edlund F, Lodén M. A double-blind and controlled study on the influence of the vehicle on the skin susceptibility to stinging from lactic acid. Int J Cosmet Sci. (2007)