Antioxidants Used in Skin Care Formulations

I. Bogdan Allemann, MD; L. Baumann, MD


Skin Therapy Letter. 2008;13(7):5-8. 

In This Article

Abstract and Introduction

The formation of free radicals is a widely accepted pivotal mechanism leading to skin aging. Free radicals are highly reactive molecules with unpaired electrons that can directly damage various cellular structural membranes, lipids, proteins, and DNA. The damaging effects of these reactive oxygen species are induced internally during normal metabolism and externally through various oxidative stresses. The production of free radicals increases with age, while the endogenous defense mechanisms that counter them decrease. This imbalance leads to the progressive damage of cellular structures, and thus, results in accelerated aging. Antioxidants are substances that can provide protection from endogenous and exogenous oxidative stresses by scavenging free radicals. Topical antioxidants are available in multivariate combinations through over-the-counter skin care products that are aimed at preventing the clinical signs of photoaging.

Skin aging is a complex process involving various genetic, environmental, and hormonal mechanisms. One can differentiate between intrinsic, chronologic aging and extrinsic, “environmental’ aging; both processes occur in conjunction with the other and are superimposed on each other. Free radicals play a central role in the course of both intrinsic and extrinsic aging. During the chronologic aging process, free radicals are formed naturally through normal human metabolism, whereas, in the extrinsic aging process, they are produced by exogenous factors, such as UV exposure, cigarette smoking, and alcohol consumption. At least 50% of UV-induced damage to the skin is estimated to be attributable to the UV-induced formation of free radicals.1 Harman, et al. first proposed this “free radical theory of aging’ in 1956, and today it is one of the most widely accepted theories used to explain the cause of aging.[2]

Free radicals are highly reactive molecules with an odd number of electrons that are generated from oxygen;[3] they can damage various cellular structures, such as DNA, proteins, and cellular membranes. In addition, free radicals may lead to inflammation, which seems to play an additional role in skin aging.[4]

The body possesses endogenous defense mechanisms, such as antioxidative enzymes (superoxide dismutase, catalase, glutathione peroxidase) and nonenzymatic antioxidative molecules (vitamin E, vitamin C, glutathione, ubiquinone), protecting it from free radicals by reducing and neutralizing them.[5] Some of these antioxidant defense mechanisms can be inhibited by ultraviolet (UV) light.[6] Moreover, as part of the natural aging process endogenous defense mechanisms decrease, while the production of reactive oxygen species increases, resulting in accelerated skin aging.

It is intuitive to hypothesize that the topical application of antioxidants may neutralize some of the resulting free radicals, and consequently lessen or prevent the signs of aging skin. At present, topical antioxidants are marketed to prevent aging and UV-induced skin damage, as well as to treat wrinkles and erythema due to inflammation (e.g., post laser resurfacing). However, currently, only vitamin C can actually treat wrinkles by influencing collagen formation through a mechanism other than antioxidation. For other products, their ability to improve wrinkles is either due to swelling or hydrating effects, or to other formulary constituents, such as retinol and vitamin C. Hence, antioxidants can prevent wrinkles, but not treat them.

For topically administered antioxidants to be effective in preventing skin aging, a couple of considerations should be made when formulating them:

  • Product stabilization is crucial. Because antioxidants are very unstable, they may become oxidized and inactive before reaching the target.

  • They must be properly absorbed into the skin, reach their target tissue in the active form, and remain there long enough to exert the desired effects.

Many antioxidants have been used for centuries in ancient and modern cultures around the world for various diseases.[7] In addition to their antioxidant activity, most of them possess numerous other biologic properties, e.g., they can be anticarcinogenic and anti-inflammatory. This article will discuss antioxidants that are currently marketed in cosmetic formulations and will focus on their antioxidant activities.


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