Effects of Skin Lightening Cream Agents - Hydroquinone and Kojic Acid, on the Skin of Adult Female Experimental Rats

Abstract

Introduction: Skin bleaching is the act of using steroid- and chemical-containing products to lighten the skin. Hydroquinone and kojic acid are often used in skin bleaching creams. Hydroquinone was suspected to be harmful. This study investigated the effects of kojic acid and hydroquinone on the skin of adult female Wistar rats and the potential use of aloe vera for amelioration.

Materials and methods: Eighty [n=80] adult female Wistar rats with an average weight of 120 g were randomly divided into eight groups, marked A, B, C, D, E, F, G, and H. Group A animals served as the control group; group B was treated with 2% hydroquinone, group C was treated with 2% kojic acid, group D was treated with 4% hydroquinone, group E was treated with 4% kojic acid, group F was treated with 2% hydroquinone and 2% kojic acid, group G was treated with 4% hydroquinone and 4% kojic acid, and group H was treated with 4% hydroquinone, 4% kojic acid, and aloe vera. The preparations were applied to the tail skin and treatment lasted 28 days. Skin samples were excised and processed using H&E, Masson's trichrome, and p65 immunohistochemical assays on tissue sections.

Results: Hydroquinone caused structural disruptions of the stratum corneum of the epidermis and the overlying keratin. p65 was also prominently expressed in the treated groups. Hydroquinone reduced skin thickness and caused epidermis disruption.

Discussion: The prominent expression of p65 in the sections indicated deleterious effects of hydroquinone. Kojic acid was not found to have deleterious effects. Aloe vera prevented extensive disruption of stratum corneum by hydroquinone. The use of hydroquinone in skin lightening creams might raise health concerns. Aloe vera could be protective against hydroquinone.

Keywords: aloe vera; bleaching products; hydroquinone; kojic acid; skin.

Figure 1

Photomicrograph of the skin of the experimental animals in Groups A–H, demonstrating the skin using H and E (H&E A-H; X400). The stratum corneum was disrupted in Groups B, D, and G (H&E B, D, and G). Note: Arrows point to specific features that are denoted by letters. Abbreviations: ED, Epidermis - (1) Stratum corneum (2) Stratum Granulosum (3) Stratum Spinosum (4) Stratum Basale; D, Dermis; G, Gland; C, Connective tissue; K, Keratin.

Figure 2

Photomicrograph of the skin of the experimental animals in Groups A–H demonstrating the skin using the Masson’s trichrome technique (MT A-H; X400). The connective tissue was relatively generally preserved in the skin layers (MT A-H). Note: Arrows point to specific features that are denoted by letters. Abbreviations: ED, Epidermis - (1) Stratum corneum (2) Stratum Granulosum (3) Stratum Spinosum (4) Stratum Basale; D, Dermis; G, Gland; C, Connective tissue; K, Keratin.

Figure 3

Photomicrograph of the skin of the experimental animals in Groups A–H demonstrating the skin using the p65 immunohistochemistry technique (p65 A-H). More cells in the groups B, D, F, and G expressed p65 which was used as an inflammation marker. Note: Arrows point to specific features that are denoted by letters. Abbreviations: ED, Epidermis - (1) Stratum corneum (2) Stratum Granulosum (3) Stratum Spinosum (4) Stratum Basale; D, Dermis; G, Gland; C, Connective tissue; K, Keratin.