Abstract
Ammonium lactate is a well-established, time-tested dermatologic therapy with a substantial body of clinical evidence supporting its use in xerotic and hyperkeratotic skin conditions. Although its use in routine practice has evolved over time, interest in ammonium lactate has been renewed by advances in the understanding of lactate biology and its role in skin physiology. Xerosis is characterized by reduced water content, impaired corneocyte turnover, and structural disruption of the stratum corneum, leading to scaling, roughness, and discomfort. As a pH-balanced source of L-lactic acid, ammonium lactate exerts biomimetic effects, aligning with physiologic skin processes. This pHdependent delivery allows effective lactic acid activity at clinically relevant concentrations while maintaining a favorable tolerability profile. Emerging insights into the role of lactate as both a natural moisturizing factor component and a regulator of epidermal function provide a more contemporary framework for understanding its clinical activity. Through combined humectant and desquamating activity, ammonium lactate boosts moisture balance, surface smoothness, and overall skin quality. Clinical evidence supports its use in conditions including ichthyosis, atopic dermatitis, psoriasis, keratosis pilaris, acanthosis nigricans, as well as visible "ashiness", a distinct clinical feature associated with xerosis in skin of color. Treatment outcomes are influenced by concentration, formulation, and disease severity, endorsing a tailored therapeutic approach. This review provides a clinically focused framework for the use of ammonium lactate, positioning it as a versatile and physiologically aligned treatment option within contemporary dermatologic practice.  .