Our blog this week addresses how to prevent and reverse post-inflammatory hyperpigmentation (PIH). And yes, that is indeed 12 syllables and quite a mouthful so we can guess your first question. What on earth is PIH? So let’s get right to it.
PIH appears as dark and flattened spots on the body, which can range in color from black to brown depending on skin tone and extent. This spottiness is caused by an enhanced synthesis and deposition of melanin in skin cells, often induced by excess exposure to the sun or other sources of harmful ultraviolet radiation. But PIH can have other triggers such as inflammatory skin conditions including acne and atopic dermatitis, allergies, injuries, hormonal changes and even cosmetic procedures such as dermabrasion, laser treatment and chemical peels. Although PIH can affect people of all ages and gender, ample evidence suggests it is more frequently observed and of greater severity in individuals with darkly pigmented skin and thus perhaps less likely to use some form of sunscreen.
PIH can originate on the outermost layers of skin (the epidermis) or the innermost (basal layers of the dermis). In either case evidence from scientific studies point to inflammation being responsible for the origin of PIH. In the former case where PIH is confined to the epidermis, there is an increase in the production and transfer of melanin to surrounding keratinocytes (the cells which account for about 90% of all cells in the epidermis) stimulated by inflammatory biomarkers such as cytokines, chemokines as well as reactive oxygen species (ROS) released by the inflammation. In the latter case where PIH occurs in the deeper basal layers of the dermis, inflammation damages the basal keratinocytes, resulting in the release of large amounts of melanin. This freed pigment is then “consumed” or phagocytosed by macrophages (a type of white blood cell essentially initiating it’s immune response to the inflammatory process) in the upper dermis generating the visible discoloration of the skin.
So how can PIH be prevented? Well, we know the important role inflammation plays, and we know that every time we scratch that itch, we wind up producing more inflammation. So as hard as it can be to resist, try not to scratch rashes or pick at pimples. And after that, the first thing everyone should do, regardless of age, gender and skin color, is always use sunscreen when outside. And if you are particularly worried because you have darker skin and may be more susceptible to PIH, you may wish to look over the ingredients of the different sunscreens available for any that include iron oxides, which are able to protect against the visible wavelengths of the solar spectrum. Though the harmful effect of the sun’s UHV rays get a lot of press, the less energetic visible wavelengths have also been implicated to some extent in the development of PIH.
Another mode of prevention and perhaps first line of therapy lies within the use of oral or topical antioxidants. We have already mentioned that ROS are complicit in aiding the production and transport of melanin that leads to PIH. It logically follows then that antioxidants will be helpful in prevention and treatment of PIH. However, our natural antioxidant levels become significantly reduced through the aging process itself combined with the cumulative effect of years of exposure to the sun’s ultraviolet rays. Ensuring we have a healthy level of antioxidants becomes key, either through dietary changes to add more natural antioxidants, or through supplementation. Also important to keep in mind is where the root cause of the PIH originates. If it is at the basal layer of the dermis, topical medications will not be terribly effective as they will be limited by the ability of their active ingredient to reach that buried site of inflammation deep within our layer of skin. Oral supplementation will have a better chance of being effective, otherwise other out-patient treatment options under the direction of a physician at your local clinic may be required.
But in terms of oral supplementation, carotenoids are especially effective for their protection against oxidative stress and free radical damage resulting from UV radiation. The most common of these include alpha- and beta-carotene, lycopene, zeaxanthin, lutein and alpha- and beta-cryptoxanthin. It is believed that these powerful antioxidants, in particular zeaxanthin and lutein (which are compounds also largely responsible for the bright colors of many vegetables and also valuable for eye health) can also contribute to the prevention of pigment deposition through reduction in inflammation, interference with free radical formation and something called tyrosinase inhibition (we’ll get to this). Polyphenols, another group of antioxidants derived from plants, are also effective in prevention of PIH. The most well-studied family of polyphenols are the flavonoids, which are believed to exhibit their antioxidant effect through inhibition of tyrosinase-catalyzed oxidation (there is that word again) and scavenging of ROS.
Now back to tyrosinase…what is it, and why would I want it inhibited? Tyrosinase is an enzyme (a biological catalyst, hence use of the phrase “tyrosinase-catalyzed oxidation” in the previous paragraph) which plays an important role in the process by which melanin is produced and in enzymatic browning (cut an apple open and let it sit in air for a bit and you will see “enzymatic browning” of its flesh). You may now start to see why tyrosinase inhibition would be a helpful process in the context of PIH. As we mentioned above, polyphenols, flavonoids are excellent sources but others can be found in fungi and even bacteria. An exhaustive, peer-reviewed study with an extensive list of many different sources of tyrosinase inhibitors has been recently published.
Take away message
In this week’s blog we discussed how to prevent and reverse post-inflammatory hyperpigmentation (PIH). We started by giving a description of PIH and how it can form, either on the outermost or innermost skin layers. Prevention mechanisms include resisting the urge to scratch or pick at rashes or pimples, always wearing a sunscreen outside and ensuring you are maintaining adequate levels of antioxidants. If you feel you need supplementation, carotenoids and flavonoids are excellent choices but we also discussed tyrosinase inhibitors and how they can be equally effective against PIH, as well as providing an exhaustive list of compounds that have been found to be effective tyrosinase inhibitors.