One of the most bothersome and disfiguring characteristics of cutaneous inflammatory conditions such as acne and rosacea is not the condition itself, but the residual discoloration or hyperpigmentation that is left behind. Even with efficacious treatments, this hyperpigmentation can linger for months.
But why is that? How can pimples disappear after one week, while the resulting postinflammatory hyperpigmentation remains present after ten weeks?
The answer lies in the functional mechanisms of the various skin lighteners used in topical therapy and how they combat melanogenesis.
How Is Melanin Produced?
Melanin synthesis can be triggered by a variety of oxidative and inflammatory compounds. The most notable instigator is of course, UV radiation, which is a source of oxidative free radical damage. This free radical damage triggers DNA repair, which is what stimulates melanogenesis. However, free radical damage can lead to the increase of inflammatory mediators such as the interleukins and prostaglandins, which have been shown to also trigger melanogenesis. And in inflammatory conditions, these mediators are prevalent throughout the skin.
As we learned in What Is the Biology of Skin Color, after contact with the various triggers mentioned above has been made, cells called melanocytes will begin to produce melanin. After the melanin is made, vesicles called melanosomes distribute the melanin throughout the epidermis. Once they reach the target area, the melanin is deposited—this is what you see on the skin.
So What’s with the Delay?
Unfortunately, almost every well-documented and effective at-home topical treatment inhibits the steps of melanogenesis, rather than the melanin that’s already been produced. Remember, THAT’S the source of the hyperpigmentation!
The only notable topical ingredient that can diminish existing hyperpigmentation is glycolic acid, and to an extent salicylic acid. These hydroxy acids (primarily the former) induce chemoexfoliation of the entire surface of the skin. By increasing “cellular turnover” by stimulating the skin to shed the outer layer of cells, glycolic acid quickens the eventual shedding of the excess melanin that’s sitting at the bottom of the epidermis. However, there is one caveat to this ingredient: in order to induce this type of controlled damage; at-home glycolic acid products (5-20%) do not possess the strength to significantly reduce hyperpigmentation.
What does that Mean?
It can feel like it is taking so long to treat hyperpigmentation. However, this doesn’t mean that these ingredients aren’t effective. They are, in fact! Hundreds, possibly thousands of studies have proven that they can provide statistically significant reductions in hyperpigmentation compared with baseline values. Just don’t expect drastic results when dealing with moderate to serious hyperpigmentation.
The most important thing that you can do is to be patient and allow your skin to naturally fade any hyperpigmentation, while consistently using sunscreen and the various topical remedies available—in this case, the more the merrier.