Dual Effects of Alpha-Hydroxy Acids on the Skin

Abstract

AHAs are organic acids with one hydroxyl group attached to the alpha position of the acid. AHAs including glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid are often used extensively in cosmetic formulations. AHAs have been used as superficial peeling agents as well as to ameliorate the appearance of keratoses and acne in dermatology. However, caution should be exercised in relation to certain adverse reactions among patients using products with AHAs, including swelling, burning, and pruritus. Whether AHAs enhance or decrease photo damage of the skin remains unclear, compelling us to ask the question, is AHA a friend or a foe of the skin? The aim of this manuscript is to review the various biological effects and mechanisms of AHAs on human keratinocytes and in an animal model. We conclude that whether AHA is a friend or foe of human skin depends on its concentration. These mechanisms of AHAs are currently well understood, aiding the development of novel approaches for the prevention of UV-induced skin damage.

A 10% Lactobionic acid‐containing moisturizer reduces skin surface pH without irritation—An in vivo/in vitro study

“…However, all of the investigated formulations contained AHAs, while only few studies focused on their safety, or they used subjective methods of skin safety investigations which are normally considered unreliable . It is worth mentioning that, despite their widespread use, there is still a concern about the safety of AHAs . As we mentioned in the Introduction section, the issue of emulsion vehicle for AHAs is also being taken for granted.…”

“…23 It is worth mentioning that, despite their widespread use, there is still a concern about the safety of AHAs. 24 As we mentioned in the Introduction section, the issue of emulsion vehicle for AHAs is also being taken for granted. For example, commonly used acid-stable excipients like polyethylene glycols (PEGs) could provoke erythema and increase TEWL in treated skin.…”

Topical cream with live lactobacilli modulates the skin microbiome and reduce acne symptoms

“…These lipase enzymes are involved in inflammation of the skin induced by C. acnes , because they metabolize sebum into free fatty acids which may lead to skin irritation 5 . Furthermore, because lactic acid has a strong antimicrobial activity 35 , as well as a documented dose-dependent capacity to ameliorate the appearance of keratoses and acne in dermatology 36 , we also substantiated lactic acid production by the selected lactobacilli (Figure 2d). Furthermore, we validated that the three selected lactobacilli did not exhibit toxic or overt inflammatory responses on primary skin cells (Figure 2e), in agreement with genome predictions 22-24 and laboratory validation of antibiotic resistance profiles according to the guidelines of the European Food Safety Authority (EFSA) 37 .…”

Glucose Exerts an Anti-Melanogenic Effect by Indirect Inactivation of Tyrosinase in Melanocytes and a Human Skin Equivalent

“…Lactic acid is an alpha hydroxy acid (AHA); these acids are used extensively in cosmetic formulations as superficial peeling agents [25]. In addition, lactic acid suppresses melanin formation by directly inhibiting tyrosinase activity, an effect independent of its acidic nature, which means that lactic acid's effects on pigmentary lesions are due not only to acceleration of epidermal cell turnover, but also direct inhibition of melanin formation in melanocytes [15].…”