Hydroquinone for lightening of skin pigmentation
Hydroquinone is one of the best-established topical agents for reducing skin pimgentation, often viewed as the golden standard of skin lightening. Its effectiveness, both alone and in combination with other treatments, has been documented in a large number of clinical studies. It works by inhibiting the enzyme tyrosinase, thus blocking a critical step in the synthesis of melanin (dark skin pigment). Hydroquinone does not bleach skin in the sense that it does not destroy previously synthesized melanin. Hydroquinone treatment usually takes several weeks to produce results because even though the synthesis of new melanin is blocked quickly, the existing melanin takes a relatively long time to migrate out of the skin in the process of natural exfoliation. To speed up the effects, hydroquinone or other melanin synthesis inhibitors are sometimes combined with exfoliating agents, such as alpha-hydroxy acids.
Retinoic Acid is used for reversal of skin damage caused by excessive UV exposure and improvement of acne related skin condition.
Retinoic acid (Stieva A/RetinA) produces multiple effects in the skin. It works by triggering molecular switches in skin cells called retinoid receptors. These switches affect many intracellular processes including cell growth and differentiation, synthesis of proteins (including collagen and elastin), sebum production, and possibly even the cell’s lifespan clock (telomeres). Furthermore, tretinoin indirectly inhibits matrix metalloproteinases (MMP), the enzymes that break down collagen and elastin, the skin’s key structural proteins. MMP become overactive as we age and contribute to wrinkles and sagging skin. Overall, the biochemical effects of tretinoin are numerous.
Retinoic acid and its analogs (collectively called retinoids) are among the very few substances whose anti-aging effects on the skin have been documented in many well-designed studies of varying duration. Topical tretinoin was found to reduce fine wrinkles and skin roughness, increase epidermal thickness and stimulate deposition of collagen. Typical strength of topical tretinoin creams is 0.025 – 0.1 percent. Side effects are not uncommon and include skin-irritation, dryness, peeling and sun sensitivity. With tretinoin, more is not necessarily better. Studies indicate that 0.025 percent tretinoin may be almost as effective as 0.05 or 0.1 percent, but with lower incidence of skin irritation. According to the studies, improvement on tretinoin may continue for up to a year of continued use.