UV Rays and Hyperpigmentation
Why Does Sun Exposure Lead to Hyperpigmentation?
To put in short, the answer is melanin. More specifically, the ‘protective’ nature that melanin possesses. Melanin is a black (eumelanin) or brown (pheomelanin) colour pigment that is created by the dermal melanocyte. The volume and type, as well and the ratio of distribution is what determines one’s skin colour.
Moreover, melanin is naturally a great defence against UV rays. Once the skin is exposed to the sun, melanin utilizes it’s defence mechanism by either absorbs or distributes it, resulting in the darkening effect but simultaneously protecting the skin from the harsh, negative effects of sun exposure.
This protects the cell DNA and stops it from making significant damage to the skin. Visible increase of pigmentation in the skin would mean that the melanin within is working extra hard to protect the skin.
Now, let’s take a closer look at just exactly how the process of hyperpigmentation works within the skin and how to combat hyperpigmentation under the scorching sun.
The Process of Hyperpigmentation
STEP 1
The Initial Detection of Cells Created by UV Rays
Once the skin is exposed to UV rays, the skin uses multiple stages to detect said exposure and signals to the melanocyte at basal layer of the skin to start creating melanin pigments. Initially, UV rays activates p53, a transcription factor in keratinocyte, which reacts with the hormone Q-MSH, which stimulates melanocyte. This fusion of the two elements create a-MSH, which is accepted by a receptor that is found on the cell membrane called MV1R. The fusion of -MSH and MC1R increases the production of MITF, one of the most important factors towards melanin production, as well as Tyrosinase, a catalyst enzyme that accelerates the production of melanin.
STEP 2
Controlling the Active Enzymes that Affects Melanin Production
Increased production of tyrosinase starts the bonding of melanin. A sub section of melanocyte called melanosome (almost a pigment factory) creates L-tyronsine, a precursor to melanin and a type of amino acid. This is then transformed into DOPA through enzymes, before finally transforming into dopaquinone. Then, the dopaquinone changed into melanin by TRP.1 and TRP2. In this process, the involvement of glutathione or cysteine would result in red and yellow pheomelanin, and black eumelanin if not.
STEP 3
The Movement and Settlement of Melanin Cells Through Melanosome
Once the melanosome is filled with the melanin pigments, it moves to the rear end of melanocyte called dendrite, which is how it spreads the pigment to the keratin cells.
Just like how a product is produced, packaged and shipped off in a factory, this is the process of how melanin is formed in melanosome then sent up to the most outer keratin layer. The melanin pigments that situates within the keratin cells naturally follows the cell’s turnover period to move and transform until it finally reaches the external layer and leaves the skin.
The Negative Effects of UV Rays
The negative effects of UV rays doesn’t stop at hyperpigmentation, it is merely a side effect of the damage sun exposure can cause. The more the skin is exposed to sunlight and UV rays, it is more prone to things such as the damage of skin cell DNA, stressed oxidation, loss of elasticity due to the destruction of collagen, an overall deterioration of the skin including the weakening of skin barrier, and in worst case, can cause skin cancer as well.
However if there is an unusual increase in spotty hyperpigmentation, or if it doesn’t seem to fade over time at all, it might be a signal that photodamage might also be in progress. In conclusion, the damage that UV rays cause doesn’t stop at some pigmentation, it could have a domino effect in breaking down the skin to the core step by step.
DNA DAMAGE
Prolonged exposure to UV rays can sever the chain structure in the cell nucleus. This could result in a halt to cell division, self-destruction of cells or mutation of cells during the repair process which can lead to skin cancer.
ROS INCREASE
Constant sun exposure stimulates irregular activities of the reactive oxygen species (ROS) within the mitochondria in the cells. The body has a natural defence system against ROS, however UV rays retrains this system from coming to action, allowing oxidative damage to occur.
MMP INCREASE
If the UV ray penetrates into the dermal layer, it activates MMP enzymes with is an ingredient that destroys collagen cells, elastin fibres and extracellular matrix. This process can weaken the structural integrity of the skin cells, causing spaces in between which could result in wrinkles.
BARRIER WEAKENING
The keratin layer of the skin, which is the most outer layer, is the very first defensive step against exposure to UV rays. The radiant heat of the UV rays weakens the bond between cells, resulting un unnecessary keratin exfoliation. It also lowers the moisture level of the skin by accelerating the reduction of NMF, a natural moisture retaining gene.
How to Combat Hyperpigmentation Under the Scorching Sun
Hyperpigmentation is very difficult to reverse, which is why it is so important to make sure it doesn’t occur in the first place.
Some hyperpigmentation caused by the sun might show up on the skin within 2-3 days after the exposure, but the built up pigment usually fully shows up in the fall after the summer heat dies down. This is why it is crucial to start preparing for the defence against sun exposure in June before the burning heat actually starts.
Blocking UV Rays Using Sunblock
Using a sunscreen on a daily basis and avoiding direct exposure to sunlight is the most basic yet effective way to prevent hyperpigmentation caused by UV rays. Creating a life pattern that completely avoids sun exposure might be difficult, so making a habit of using a sunscreen that is at least SPF30 PA+++ that has a well balanced mix of UVA and UVB filters is extremely important.
To maximize the effects of sunscreen, the amount and method of using is crucial to remember. The amount of sunblock should be about 2/3 of a finger (2mg/cm2), and apply about 30 minutes before the sun exposure. Reapplication every 2-3 hours is also important, especially in the summer where sweat and other factors can erase it away.
Inducing the Exfoliation of Pigmentation Through Peeling Treatments
In order to escape the vicious cycle of pigmentation continuously building up, a peeling treatment that can exfoliate the pigmented external layer is periodically necessary. If the skin is constantly exposed to UV rays, not only does pigment start to build up, the turnover period for dead skin cells also slows down, resulting in more buildup of pigment within the skin cells. This is also the reason why photo-damaged skin feels a lot tougher to the touch. In order to avoid this, regular peeling treatment that uses ingredients that not only exfoliates but also has brightening, anti-oxide and moisturizing qualities would be the ideal method of treatment. Some examples of this includes glycolic acid, citric acid, pythic acid, mandelic acid, magic acid, and pyruvic acid, and/or softer enzymes. However, alway be cautious when using peeling treatments in the summer where there is an increased amount of sun exposure as stronger peels that are not scheduled out properly might actually overstimulate the melanin pigments which could lead to more hyperpigmentation.
Brightening Care Targeting Pigments
The biggest key point in brightening care is usually one of three things; suppressing the tyrosinase enzyme that stimulates the biosynthesis of melanin, or preventing the oxidation of tyrosine which is a precursor of melanin, or blocking the migration and expansion of the melanin pigment.
Some brightening ingredients that are currently approved by the Korean FDA includes; mulberry extract that stops the activation of tyrosinase, arbutin, alpha-bisabolol, licorice extract and vitamin C derivatives such as a ascorbyl glucoside, ascorbyl tetraisopalmitate, ethyl ascorbyl ether), and niacinamide, an ingredient that slows down the transfer of melanin between the skin layers. It is ideal to combine these ingredients with other melanin-targeting ingredients that also has brightening effects, and prevents and repairs the damages done by oxidation such as vitamin E, glutathione and flavonoids.
Don't forget about soothing/moisture care
When the skin gets exposed to direct sunlight, the heat gets trapped within the skin causing the skin to get red and sensitive, and/or dryer which makes it more prone to hyperpigmentation. If the redness from the sun continues, it could lead to inflammation that expands capillary vessels causing more redness, while also interfering with the body’s ability to contract. The continued stress on the skin can lead to the skin using melanin production as a defence mechanism.
In these cases, ingredients that has immediate soothing and anti-inflammatory qualities such as aloe vera, azulene and centella extract, along with moisture retaining ingredients such as hyaluronic acid, glycerol, panthenol, and lastly skin barrier strengthening ingredients such as ceramide and cholesterol should be added to the skincare routine.