The Role of Linoleic Acid in Skin and Hair Health: A Review

Abstract

Lipids are intimately associated with skin condition. This review aims to discuss the function of linoleic acid (LA, 18:2, ω-6), an essential fatty acid, in skin health and hair growth. In skin, LA can be metabolized into ω-6 unsaturated fatty acid, oxidized derivatives and incorporated into complex lipid molecules, including ω-hydroxy-ceramides. Previous research has revealed that skin diseases including acne, atopic dermatitis and psoriasis are associated with disordered LA metabolism. Studies based on animal or skin cell models suggest that LA or LA-rich vegetable oils, topically applied, exhibit diverse biological activities, including the repair of the skin barrier, the promotion of wound healing, skin whitening, photoprotection, anti-inflammatory effects and the stimulation of hair growth. Moreover, the underlying mechanisms of LA's beneficial effects on skin are summarized. Further research on the correlation of LA metabolism and skin disorders, a deeper exploration of the mechanisms underlying the function of LA in skin management and more investigations of its clinical application are required to enhance the understanding and utilization of LA in cosmetics and pharmaceuticals.

Keywords: hair growth; linoleic acid; lipid; skin barrier.

Figure 1

The metabolic pathways of linoleic acid. LA: linoleic acid; GLA: γ-linolenic acid; DGLA: dihomo-γ-linolenic acid; AA: arachidonic acid; 9-HpODE: 9-hydroperoxy-10E, 12Z-octadecadienoic acid; 13-HpODE: 13-hydroperoxy-9Z, 11E-octadecadienoic acid; 9/13-HODE: 9/13hydroxyoctadecadienoic acid; 9/13-oxo-ODE: 9/13-oxo-octadecadienoic acid; ELOVL: elongase of very long chain fatty acids; COX: cyclooxygenase; LOX: lipoxygenase.

Figure 2

Effects of linoleic acid on skin and hair growth. LA or LA-rich vegetable oils, topically applied, exhibit various effects, including the repair of the skin barrier, the promotion of wound healing, skin whitening, anti-aging and the stimulation of hair growth. LA can enhance the skin barrier via its incorporation into CER[EOS], the regulation of epidermal differentiation and the promotion of lipid production; LA facilitates wound healing via the promotion of skin hydration, enhancement of the migration of neutrophils and keratinocytes and acceleration of the inflammatory process; LA application can promote epidermal peeling, inhibit tyrosinase activity and subsequently melanin synthesis, thereby achieving the purpose of whitening. The anti-aging effects of LA are controversial. LA may induce apoptosis and promote aging, while it may inhibit MMP-2 activity, thereby reducing collagen degradation and achieving anti-aging effects; LA can regulate hair growth-related pathways and growth factors, thereby influencing the hair growth cycle.