RESUMEN
Many products had been used as chemical peeling agents to renew thin skin. Retinoic, Glycolic and Salicylic acids were used in many dermatological diseases with hypdrkeratinization and/or hyperpigmentation. To evaluate and compare the effects of these acids on the thin skin of adult female guinea pig. Twenty animals were used and were divided into four equal groups. Group I served as the control group, whereas the other treated groups were topically applicated daily on shaved area of back skin with Retinoic [0.05%], Glycolic [12%] and Salicylic [10%] acids in Groups II, III and IV, respectively. Thin skin specimens were processed for light and transmission electron microscopic studies. Morphometric and statistical studies were done. Groups II, III and IV showed high significant increase in mean thickness of epidermal nucleated keratinocytes as compared to Control group. Group II showed proliferation hyperkeratosis and acanthosis and shrinkage of the sebaceous glands with decreased sebum production. Group III showed skin peeling by removing superficial layers of epidermis, cytoplasmic and nuclear degeneration with disruption of intercellular junctions and degeneration in melanocytes with marked decrease of melanin. Both Retinoic and Glycolic acids apparently increased the production of collagen and elastic fibers as compared to control. Group IV showed skin peeling mainly by direct action on intercellular cement substance and partially by inducing proliferation hyperkertosis. Both Retinoic and Glycolic acids showed complementary actions in treatment of hyperpigmentation and as chemical peeling agents. Salicylic acid also is a peeling agent, but its effects could be covered by either Retinoic or Glycolic acids. It is recommended to use combination of both Retinoic and Glycolic acids to give better effects on various skin disorders with hyperkeratinization and hyperpigmentation