Depigmenting agents or skin bleaching-lightening agents are cosmetic products whose function is to correct some of the skin hyperpigmentations (skin spots that appear on the skin over time). This paper addresses the origin of hyperpigmentation, the methods of skin color lightening, and the different depigmenting substances used.
Hyperpigmentations can be produced or aggravated by different factors such as internal treatments with photosensitizers (sulfa or estrogen) or external (Roentgen or ultraviolet rays, cosmetics). Hyperpigmentations have also been recorded in cases of gynecological, pituitary, thyroid, or adrenal disorders. Lately, it has been observed that the use of anovulatory, mixtures of estrogens and progestogens than condition a state of artificial pregnancy, also cause hyperpigmentation.
Two of the main methods to clarify skin color by reducing skin pigmentation are: bleach already formed melanin, and prevent new melanin from forming (can be inhibited by applying an appropriate agent).
Black skin contains a large amount of melanin pigment in the outer corneal layer, and it can be discolored by oxidation with hydrogen peroxide or, more frequently, chemically reduced to its white form, which is colorless, with Hydroquinone cream.
Inhibitors of the enzyme tyrosinase
Such as 4-isopropyl catechol or hydroxyquinone monomethyl ether, which have toxic activity on melanocytes. The enzyme tyrosinase modifies these molecules. It converts them into toxic products capable of destroying melanocytes. It is not recommended to use this type of substances in cosmetic products.
They are used in cosmetic formulations, but at doses not exceeding 2% (concentration limited by regulations), since, at higher concentrations, they can cause redness and skin burns. The bleaching action is weak and only shows up after applying for a few weeks or even months; It disappears when you stop applying the Benoquin cream. Its method of the act is not very well clear. Still, it is believed to interfere with the formation, melanization, and degradation of melanosomes.
These products can cause risks of skin irritation at certain doses, so it is recommended to reduce their concentration and increase their activity with the presence of additives also depigmenting, as is the case with ascorbyl palmitate at concentrations of 1-5% or 2% tetrahydroxybenzophenone.
It is recommended that all products bearing hydroquinone derivatives carry a caution label because exposure to solar radiation can quickly reverse the bleaching effect. Also, the solutions darken when exposed to air as a result of oxidation and have to be properly stabilized. The oxidation is very fast if the solution is alkaline. They will have to be stabilized with antioxidant products such as ascorbic acid, citric acid, or sodium metabisulfite. The preparations should preferably be slightly acidic (pH 4-6), and the manufacturing equipment should be made of stainless steel or vitrified to prevent discoloration. It is suggested to reduce get in touch with air.
Hydroquinone preparations should be applied 2-3 times a day over several months, but due to repeated use or excessively high concentrations, local irritation may occur, and treatment should be discontinued.
It cannot be used in areas near mucous membranes, in wounds, or erythematous areas due to sun exposure. They should not be used in children. The pharmaceutical firms are solutions, ointments, creams, and gels.