Why post-inflammatory hyperpigmentation?

Post-inflammatory hyperpigmentation (PIH) is an excessive increase or uneven distribution of melanin in the skin following an inflammatory response. Any agent that causes skin damage or irritation can cause post-inflammatory hyperpigmentation.
The pathogenesis of post-inflammatory hyperpigmentation occurs as follows:
Inflammation stimulates the production and oxidation of arachidonic acid. This leads to increased production of inflammatory substances such as leukotrienes, cytokines, chemokines, prostaglandins and other inflammatory mediators (this is also the mechanism by which prevention of post-inflammatory hyperpigmentation with topical corticosteroids is desirable. targeted) Inflammatory mediators stimulate melanocytes to increase the production of melanin pigment under the skin and increase the transport of melanin to the surrounding area. There are two mechanisms for postinflammatory hyperpigmentation in the dermis. The first mechanism is that the inflammatory process breaks down the basal cell layer of the epidermis, leading to the release of melanin pigment into the papilla in the dermis. Macrophages in the papillary dermis will phagocytize and release melanin. The second mechanism is that macrophages can enter the epidermis to phagocytize melanosomes there and then return to the dermis. Melanin pigment can persist in macrophages in the dermis for many years.

When the skin is damaged or irritated, it can lead to tanning, post-inflammatory hyperpigmentation. This is a condition caused by an uneven distribution or overproduction of the skin pigment melanin following an inflammatory process. Postinflammatory hyperpigmentation is usually caused by damage to the epidermis and/or dermis with intracellular melanin deposition in the stratum corneum and/or dermis. The inflammatory response in the epidermis stimulates the synthesis and migration of melanocytes. If the damage is deep down the basement membrane to the dermis, the melanocytes will be trapped there.
Causes of post-inflammatory hyperpigmentation are divided into 2 main groups:
Endogenous causes: common acne, insect bites, skin infections, contact dermatitis - allergies, atopic dermatitis , psoriasis , lichen planus ... . Exogenous causes: burns, trauma, non-ionizing radiation treatment, needle roller, peeling, laser (invasive and non-invasive), light poisoning, some drugs such as Cyclin antibiotics (tetracycline) , antimalarial, clofazimine, anticancer drugs such as Bleomycin, 5-fluorouracil, doxorubicin and busulfan... Cosmetic procedures cause thermal and mechanical effects on the skin. Thereby creating a local inflammatory reaction, forming hyperpigmented halos that spread around. Factors associated with the severity of post-inflammatory hyperpigmentation associated with cosmetic procedures include: depth of invasive procedure, length of pulse width of lasers, and heat applied to the skin. intervention, the interval between the interventions is too close to each other so that the skin has not been able to regenerate and recover, cosmetologists do not understand the mechanism of action as well as the technical parameters that need to be set individually for each patient.
In addition, people with the following factors also have an increased risk of post-inflammatory hyperpigmentation:
Sunlight: Under the effect of sunlight, it will stimulate melanocytes to increase the production of melanin. Therefore, avoiding the sun and applying sunscreen is one of the important factors to prevent PIH. Dark skin: although all skin types can develop postinflammatory hyperpigmentation, it is more common in darker skinned individuals, especially when the dermatitis affects the underlying layer, through the basement membrane of the epiglottis. skin (such as a rash caused by an allergic reaction to a drug), the skin may darken for a long time. Many studies show that in dark-skinned people, the amount of melanin is more, so it is easier to develop post-inflammatory hyperpigmentation than light-skinned people. As a result, Asians have darker skin types, so PIH occurs more commonly, accounting for up to 50% of cases, and is often more severe than Caucasians. This significantly affects the aesthetics and quality of life of the patient. Persistent and recurrent skin inflammation increases the risk and severity of postinflammatory hyperpigmentation due to damage to the epidermal barrier. Damaged skin that is constantly pressed or rubbed, wet or peeled prematurely will be prone to post-inflammatory hyperpigmentation, even more severe and prolonged hyperpigmentation.

Postinflammatory hyperpigmentation often has the following manifestations:
Appears hyperpigmentation maculopapular in the healed skin after previous injury. The macules are gray, brown, or black in color and darker than the rest of the skin. Superficial (epidermal) hyperpigmentation: brown, dark brown or black macules, clearly visible under Wood's light, may resolve spontaneously without any treatment after several months to several years. Deep skin hyperpigmentation (under the epidermis): blue-gray inlaid, not clearly visible under Wood's light, if left untreated, it can be permanent or disappear after a very long time.

Post-inflammatory hyperpigmentation does not leave scars and can improve over time, but it takes a long time (3-24 months) for the pigmentation to fade. Recovery time is long or short depending on the nature of the damage, the type of skin color and the severity of the sun's impact. Specifically, post-inflammatory hyperpigmentation in young people has a better prognosis than in the elderly, damage to the epidermis has a better prognosis than that of the dermis.

Avoiding direct sunlight and applying sunscreen is the first and most important step in the treatment of post-inflammatory hyperpigmentation. Apply a broad-spectrum sunscreen with SPF 50+ every day, or take a sunscreen pill or a combination of the two to achieve the highest effectiveness, protect the skin from the harmful effects of ultraviolet rays. Avoiding the sun by not going out in the hot sun, wearing a wide-brimmed hat, long-sleeved clothes, and wearing a dark mask will help increase skin protection from the sun.
Post-inflammatory hyperpigmentation can be improved with topical agents, through inhibiting melanoma formation. However, topical application should be combined with effective sun protection. Currently, there are many topical drugs that can lighten the skin, fade dark spots due to hyperpigmentation lesions in the epidermis. The degree of improvement varies from person to person, but when combined together can give a marked improvement: Hydroquinone, Azelaic acid, Retinoid, Corticosteroids, Cysteine ​​Cream, Vitamin C, Glycolic acid. There are also Kojic acid, licorice, arbutin, niacinamide, mequinol, N-acetyl glucosamine. These drugs need to be applied at least 2 weeks before the laser procedure.
Invasive cosmetic procedures for post-inflammatory hyperpigmentation include: chemical peels, invasive laser treatments, needle rollers, skin abrasions, etc., useful for hyperpigmentation due to lesions damage the epidermis. The treatment mechanism is through stimulating the regeneration of the epidermis, creating a way for the pigments to escape deep under the skin, helping the skin become smooth and youthful. However, these methods are less effective against PIH in the dermis and can sometimes aggravate post-inflammatory hyperpigmentation if the epidermis is damaged.
Non-invasive cosmetic procedures to treat post-inflammatory hyperpigmentation such as phototherapy, long pulse laser, short pulse laser,... penetrate deep into the dermis, destroy and remove the melanocytes in deeply without damaging the skin surface. Not only that, these treatments also regenerate the skin from the inside, stimulate collagen production, help skin stretch and better elasticity.

Treatment of concomitant skin diseases improves the effectiveness and shortens the recovery time of post-inflammatory hyperpigmentation.
Good treatment of background skin diseases such as acne, psoriasis, contact dermatitis, seborrheic dermatitis, atopic dermatitis, ... reduce inflammation. Avoid causing further impact on the damaged skin. Do not soak in water, remove grinding and stretch the skin. Limit the use of drugs that increase skin pigmentation such as Tetracycline, Bleomycin, ... Gentle skin care with non-irritating cleaning products, moisturizers. Do not abuse cosmetics, especially cosmetics of unknown origin. Because they often contain heavy metals or high levels of corticosteroids, they will cause severe skin damage, make the skin discolored and difficult to recover. Postinflammatory hyperpigmentation is an excess or uneven distribution of melanin in the skin following an inflammatory response. Postinflammatory pigmentation can be caused by a variety of factors. Post-inflammatory hyperpigmentation does not leave scars, but it takes time to heal and treat.
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