Acne, eczema, rosacea, and other skin issues are undoubtedly troublesome, but red and brown acne marks, pigmentation, are equally bothersome.
To effectively and quickly make them fade away, it's important to understand that red and brown acne marks and pigmentation have fundamental differences, and therefore, the methods of care are not the same.
Let's explain their differences to help you understand how to distinguish between the two, and the correct and most effective ways to prevent, improve, and lighten them!
(Due to the length of the content, we have already discussed how to prevent and improve the red ones. For details, refere to How to Prevent and Improve Post-Inflammatory Erythema .)
The human skin consists of the epidermis, dermis, and subcutaneous tissue. If the damage caused by acne reaches the dermis and subcutaneous tissue, the skin may develop indentation scars, such as craters and icepick scars. These depressed acne scars are difficult to treat with topical skincare products alone, but retinoids, acid-based products, microneedling, and exosomes can help improve these scar issues to some extent.
On the other hand, acne marks and post-inflammatory hyperpigmentation refer to the red or brown marks left behind after acne and inflammation heal. In dermatology, the pink or red marks are called Post-Inflammatory Erythema (PIE), while the brown marks are referred to as Post-Inflammatory Hyperpigmentation (PIH).
Most people would categorize them as the same type of things, but their mechanisms of appearance are completely different, hence the methods of improvement also differ.
After acne, inflammation, or trauma, the appearance of brown marks and spots on the skin is referred to as Post-Inflammatory Hyperpigmentation (PIH) in dermatology.
| Causes of Post-Inflammatory Hyperpigmentatio
Inflammatory Skin Conditions
- Acne: Inflammation associated with acne may stimulate melanocytes (cells that produce melanin) to overproduce melanin, leading to the formation of brown acne marks.
- Eczema: Scratching due to itching from eczema can cause skin damage, inflammation, and subsequent post-inflammatory hyperpigmentation.
- Psoriasis: Inflammation associated with psoriasis can also lead to post-inflammatory hyperpigmentation.
- Allergic Reactions: Skin allergic reactions to allergens or irritants can cause inflammation, leading to post-inflammatory hyperpigmentation.
Skin Trauma
- Cuts, burns, insect bites, or any form of skin injury can stimulate melanocytes in the skin to produce more melanin during the healing process, resulting in post-inflammatory hyperpigmentation.
Exposure to Sunlight
- Ultraviolet (UV) rays can stimulate melanocytes to produce more pigment. In other words, if exposed to sunlight after already having post-inflammatory hyperpigmentation (i.e., after inflammatory skin conditions or skin trauma), the hyperpigmentation issue will worsen, and the brown marks and patches will become darker.
| Mechanism of Post-Inflammatory Hyperpigmentation
Inflammatory Response
- When the skin experiences inflammation due to conditions like acne, eczema, psoriasis, dermatitis, etc., immune cells release inflammatory mediators, such as inflammatory cytokines and other signaling molecules. These mediators then stimulate the production and release of melanocyte-specific factors.
Melanin Production
- Melanin is responsible for skin color and protecting the skin against UV radiation.
- These melanin are produced by melanocytes located in the basal layer of the epidermis in specialized organelles called "melanosomes".
- During skin inflammation or injury, as part of the immune response, the skin signals melanocytes through melanocyte-specific factors to stimulate the activity of tyrosinase, leading melanocytes to produce a large amount of melanin in originally colorless melanosomes, and gradually darkening the skin.
Melanosomes Transfer
- Once melanin-filled melanosomes mature, these melanosomes would slowly transfer in large quantities from melanocytes to nearby keratinocytes, which are predominant in the epidermis.
- This transfer process causes the inflamed or damaged area itself, as well as the surrounding skin, to darken, resulting in the formation of brown marks or patches of post-inflammatory hyperpigmentation.
Persistence of Pigmentation
- Once the epidermal cells are filled with mature melanosomes, they would slow down the skin cell renewal cycle and gradually accumulate in the various skin layers.
- If coupled with thickened stratum corneum and slow skin renewal rate, these pigmented epidermal cells will continue to remain in the epidermis without shedding, leading to long-lasting PIH brown marks or patches.
- In some cases, even after the initial inflammation subsides, excessive melanin production and transfer would continue, resulting in persistent pigmentation.
Due to fundamental differences between "Post-Inflammatory Erythema" and "Post-Inflammatory Hyperpigmentation," it is important to understand how to effectively improve and lighten them by first distinguishing between the two.
| Key Differences between Post-Inflammatory Erythema (PIE) and Post-Inflammatory Hyperpigmentation (PIH)
Color
- PIE: Pink or red marks and spots on the skin resulting from inflammation and vascular dilation.
- PIH: Brown, and sometimes gray or black marks and spots on the skin caused by excessive melanin production, melanosome transfering to keratinocytes, and over-accumulation of melanin
Characteristics
- PIE: Characterized by temporary pink or red marks and spots. They may fade upon pressure due to impaired blood circulation in the area.
- PIH: Involves actual pigment changes in the skin (excessive melanin production, melanosome transfer, and deposition in keratinocytes). They do not fade or change color temporarily upon pressure.
Duration
- PIE: Typically temporary and fades over time. However, without treatment, they may last for weeks to months and may evolve into post-inflammatory hyperpigmentation due to ongoing inflammation.
- PIH: Generally more persistent. Unless treated in time, they may last for months to years.
As shown in the image above, the causes and mechanisms behind the appearance of brown marks and spots after acne and inflammation are very complex. In fact, there is no single skincare ingredient that can target all of the skin mechanisms mentioned above. Therefore, to truly improve these brown post-inflammatory hyperpigmentation marks, relying on one single brightening ingredient is simply not enough. In fact, it is necessary to approach it from multiple angles, including:
- Soothe inflammation
- Inhibit tyrosinase activity
- Reduce the transfer of melanosomes from melanocytes to keratinocytes
- Remove melanin already accumulated in keratinocytes
| Soothe Inflammation
Since we have discuseed how to soothe and improve inflammations in our last article, we won't be repeating everything here.
For details, please refer to：How to Prevent and Improve Post-Inflammatory Erythema .
| Inhibit Tyrosinase Activity
Tyrosinase is a key enzyme involved in melanin production. When the skin experiences inflammation or injury, as part of the immune response, the skin would signal melanocytes through melanocyte-activating factors to stimulate the activity of tyrosinase. Tyrosine would then convert into L-DOPA, which would then transform into two types of melanin: eumelanin and pheomelanin.
In other words, by using tyrosinase inhibitors to prevent the conversion of tyrosine to L-DOPA, melanin production would be halted. Thus, inhibiting tyrosinase is crucial in treating post-inflammatory hyperpigmentation.
Some common tyrosinase-inhibiting skincare ingredients include:
Vitamin C
- As a potent antioxidant, vitamin C helps reduce oxidative stress that damages the skin, thereby preventing the skin from signaling melanocytes to increase tyrosinase activity. Moreover, vitamin C can directly interfere with the activity of tyrosinase, thus slowing down the rate of melanin production.
- However, it is important to note that pure vitamin C (also known as ascorbic acid or L-ascorbic acid) needs to maintain a pH level below 3.5 to remain active. Therefore, it can be highly irritating, and using it day and night can compromise the skin barrier, leading to inflammatory acne, sensitivity, peeling, and stinging issues! Hence, it may not be suitable for daily use for most skin types. Don't worry though! Vitamin C does come in various forms!
- Sodium ascorbyl phosphate (SAP), an extremely skin-friendly form of vitamin C suitable for all skin types, can also interfere with the activity of tyrosinase. In addition, clinical studies have shown that it effectively combats bacteria that cause acne, with better results and without the side effects of benzoyl peroxide! Therefore, when it comes to acne marks, it serves a dual purpose.
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Licorice Root
- Licorice root, scientifically known as Glycyrrhiza Glabra, contains over 300 elements and possesses antimicrobial, antibacterial, and anti-inflammatory properties. Therefore, it has been widely used in medicine since ancient times in countries like India, Egypt, Greece, China, and Japan. As a skincare ingredient, its benefits include antioxidant properties, inflammation soothing effects, and safe and effective skin brightening capabilities.
- One of the most effective and active elements in licorice root is glabridin, which has been proven to significantly reduce tyrosinase activity, leading to a substantial decrease in melanin production.
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Arbutin
- Arbutin is divided into three main types, including α-arbutin, β-arbutin, and D-arbutin. Among them, not only is α-arbutin the safest and most stable, it also exhibits the highest inhibitory effect on tyrosinase activity (about 10 times that of β-arbutin).
- The action of arbutin is similar to hydroquinone, which is classified as a prescription drug in Hong Kong. When applied to the skin, arbutin naturally breaks down into hydroquinone. As this conversion process takes time, the skin would not be exposed to excessive hydroquinone at once, and thus would not bring about the same side effects and risks of using hydroquinone directly.
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Azelaic Acid・Glutathione
- Azelaic acid and glutathione can downregulate the gene expression of enzymes involved in melanin production, such as tyrosinase, and can directly interfere with and thus inhibit the activity of tyrosinase,
- Additionally, azelaic acid and glutathione have anti-inflammatory properties and help protect skin cells from oxidative stress. By reducing inflammation and oxidative damage, the activity of tyrosinase can be indirectly inhibited, thus reducing the formation of melanin.
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Resveratrol
- Resveratrol is a polyphenolic compound naturally found in plants such as grape skins and Japanese knotweed. Besides directly inhibiting tyrosinase by binding to it and reducing its activity, it can also indirectly decrease the activity of tyrosinase by minimizing the damage to the skin caused by oxidative stress.
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| Reduce the Transfer of Melanosomes from Melanocytes to Keratinocytes
When melanosomes inside the melanocytes produce a large amount of melanin and thus arken, they would slowly transfer in large quantities to nearby epidermal keratinocytes. Upon accumulation to a certain extent, they would become visible post-inflammatory hyperpigmentation, manifested as brown marks or patches.
In other words, to reduce the appearance of pigmented acne marks, it is essential to intercept this transfer process.
Some skincare ingredients that can effectively inhibit this transfer process include:
Niacinamide
- Niacinamide can disrupt the signaling pathways involved in the transfer of melanosomes from melanocytes to keratinocytes, thereby preventing and reducing pigmentation.
- In addition, niacinamide can regulate melanin production in melanocytes, and reduce the amount of melanin available for transfer to epidermal cells, thus indirectly inhibiting melanosome transfer.
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Other Skincare Ingredients That Can Inhibit Melanin Transfer
- Other skincare ingredients that have been proven to inhibit the transfer of melanosomes to epidermal cells include retinol, licorice root, alpha-arbutin, mulberry extract, and more.
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| Removing Melanin Already Accumulated in Keratinocytes
Inhibiting tyrosinase activity and melanin transfer is crucial in preventing melanin accumulation in keratinocytes. But what about brown marks, patches, and spots that have already formed and are visible?
These visible marks and spots signify a build-up of melanized melanosomes within the various layers of the epidermal keratinocytes. Therefore, to improve them, it is necessary to promote cell renewal and cell turnover to reduce the number of keratinocytes laden with melanin deposits.
It is important to note that even if you're receiving any treatment in a beauty clinic claiming to "disperse" melanin, it simply means that melanin would no longer be heavily concentrated in one area, not that they have vanished completely into thin air. Ultimately, they still need to be eliminated from the epidermis through cell turnover and renewal.
Some of the most effective skincare ingredients to do this job include:
Retinol
- Retinol stimulates and accelerates the generation of new skin cells and aids in their passage through the different layers of the skin. This helps the skin shed aged cells containing excessive melanin.
- In addtion, retinol influences the differentiation of keratinocytes. When keratinocytes differentiate more regularly and systematically, skin cells can mature and shed properly, thus removing aged, over-pigmented skin cells.
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AHA and PHA
- AHAs such as lactic acid, mandelic acid, malic acid, and glycolic acid, as well as PHAs like lactobionic acid and gluconolactone, can dissolve the glue between aging keratinocytes on the skin's surface. This accelerates the natural shedding of aged cells containing excessive melanin, thereby revealing younger skin cells with less pigment deposition underneath. Furthermore, when aged skin cells shed more rapidly, it naturally stimulates the generation of new skin cells.
- On the other hand, by removing aged keratinocytes, other skincare ingredients that help improve hyperpigmentation, such as tyrosinase inhibitors and melanin transfer inhibitors, can better penetrate into the deeper layers of the skin, and reach areas where excessive melanin may be present, thereby providing more effective results.
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Licorice Root
- As mentioned above, Glabridin in licorice root has been shown to significantly reduce tyrosinase activity, while another element in it, Liquiritin, has been proven to eliminate existing excess melanin, thereby lightening already formed PIH without any side effects.
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| Use Sunscreen Indoors and Outdoors Every Day of the Year
When the skin absorbs ultraviolet rays, it triggers an inflammatory response. As part of the immune response, the skin signals melanocytes to produce more melanin. In other words, using sunscreen is the most basic step to prevent and improve PIH.
But what about on cloudy days or when staying indoor the whole day, do you still need sunscreen?
Cloudy days do not mean you are not exposed to UV radiation. While it is true that under a cloudless sky, UV levels are highest, and thick cloud cover can reduce UV radiation, thin or light clouds hardly block UV rays at all and may even enhance UV levels through scattering. Additionally, even in shaded areas like between buildings or under umbrellas, prolonged sitting under the sun can still lead to sunburn.
Furthermore, many substances reflect UV radiation, increasing the overall UV exposure on the skin. For example, grass, soil, and water reflect about 10% of UV rays, beach sand reflects about 15%, ocean foam reflects about 25%, and freshly fallen snow can nearly double the overall UV radiation!
Staying indoors does not mean you can skip sunscreen either. Glass used in cars, homes, and office windows does not completely block UVB rays. This means that even indoors, being close to windows can expose your skin to UV damage due to light and various material reflections. Studies have shown that for drivers who drive on the right, their right face and arm receive significantly more UV damage than the left side, and vice versa.
Thus, whether it's sunny, cloudy, or rainy, indoors or outdoors, it is essential to use sunscreen to protect your skin from UV radiation and prevent excessive melanin production.
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