Эстетические обработки для PIH: пигментальные лазеры и химическое пилинг

Postinflammatory Hyperpigmentation (PIH) is a skin condition characterized by excessive pigmentation following acute or chronic inflammatory stimulation. Although it has a self-limiting nature, PIH can persist for several months or even years, significantly impacting a patient’s appearance and quality of life. Currently, there is no unified, standardized consensus for the prevention and treatment of PIH in China.

In response to this gap, the Dermatology and Aesthetic Medicine Group of the Chinese Medical Association’s Aesthetic and Cosmetic Medicine Branch has recently published the “Expert Consensus on the Prevention and Treatment of Postinflammatory Hyperpigmentation (2024 Edition)” based on clinical experience and recent literature. Below is a summary of this consensus.

Epidemiological Characteristics:

1. PIH can occur at any age, with similar prevalence rates in men and women.
2. PIH is generally more prominent in Fitzpatrick skin types IV to VI. East Asian populations (including Chinese individuals) predominantly fall into Fitzpatrick skin types III and IV.
3. PIH can be caused by a variety of factors, including disease-related factors, trauma, environmental factors, iatrogenic (medical) factors, and individual predisposition. Acne is one of the most common causes of PIH, especially in individuals with Fitzpatrick skin types IV to VI.

Pathogenesis:

1. Inflammatory stimuli mediate the production of eicosanoids by keratinocytes, increasing tyrosinase activity and promoting melanin synthesis.
2. Inflammatory factors stimulate melanocytes, leading to epidermal melanin deposition.
3. Melanocytes are damaged by inflammatory attacks, causing melanin granules to shed from the epidermis into the dermis, resulting in dermal-type melanin deposition.
4. Inflammation leads to local skin metabolic dysfunction, affecting various stages of melanin formation.
5. Post-inflammatory destruction of the basal cell layer can cause pigment incontinence, with increased dermal macrophages phagocytosing the upper dermal melanin to become melanophages.

Clinical Manifestations:

1. The typical clinical manifestation of PIH is light brown to dark brown pigmented macules, which can occur on any part of the body.
2. Histologically, PIH can be classified into epidermal and dermal types, and both types may be observed in the same patient.
3. Epidermal-type PIH can resolve spontaneously within several months to several years, while dermal-type PIH may take years to resolve or may persist permanently.

Treatment Methods

1️⃣ Topical Medications

• Highly Recommended
  • Drugs that inhibit Propionibacterium acnes activity (clindamycin): commonly used concentration 2%–4%, can be used long-term during the maintenance phase.
  • Drugs that inhibit Propionibacterium acnes activity (tretinoin, adapalene, azelaic acid, ketoconazole, arbutin): can be used long-term.
  • Drugs that promote epidermal renewal and exfoliation (retinoic acid, adapalene and its analogs): take effect after more than 3 months.
  • Anti-inflammatory drugs (dexamethasone, hydrocortisone and other glucocorticoids): should not be used if there is no inflammation.
• Weakly Recommended
  • Vitamins: Vitamin E (antioxidant), Vitamin C (antioxidant).

---

2️⃣ Oral Medications

• Highly Recommended
  • Tetracycline: 0.25–0.5 g/time, 1–2 times/day.
  • B vitamins (niacinamide, vitamin B6, etc.).
• Weakly Recommended
  • Vitamin C: 0.2 g/time, 3 times/day.
  • Vitamin E: 0.1 g/time, once/day.

---

3️⃣ Chemical Peels (Highly Recommended)

• Main agents: glycolic acid, salicylic acid, lactic acid, trichloroacetic acid, mandelic acid, compound acids, etc.
• Mild peels: low concentration, short duration, mainly for closed comedones and excessive sebum secretion due to sebaceous gland hyperactivity.
• Medium/Deep peels: for early, middle, and late-stage acne; requires local antibacterial and anti-infective medications.
• Защита от солнца: avoid UV exposure; contraindicated when using hormonal drugs.

---

4️⃣ Phototherapy (Highly Recommended)

• Q-switched Laser
  • Wavelengths: 1064 nm, 694 nm (large spot size, low energy fractional mode).
• Интенсивный импульсный свет (IPL)
  • Wavelengths: 590 nm, 640 nm filters (primarily for pigmented lesions).
• Пикосекундный лазер
  • Indications: large spot size, low energy fractional mode (to avoid PIH).
• Fractional Laser
  • Wavelengths: non-ablative 1550 nm, 1927 nm (chosen based on skin type, PIH risk, and inflammation degree).

---

5️⃣ Combination Therapy

• Chemical peels combined with Q-switched laser/IPL/fractional laser treatments.
• Q-switched laser, picosecond laser, fractional laser combined with topical or oral therapies.

---

6️⃣ Traditional Chinese Medicine (TCM)

• Oral TCM: Qi and blood tonics, blood-nourishing and dampness-eliminating formulations.
• Topical TCM: Heat-clearing and detoxifying, blood-activating and stasis-removing, dampness-drying and acne-eliminating formulations.

Preventive Measures

Address Underlying Causes

• Actively Treat Underlying Skin Conditions
  • Examples: Acne, eczema, skin infections, etc.
  • Regular check-ups and reviews
• Avoid External Irritants
  • Physical Irritants Prevention
    • Comprehensive protection (wear protective clothing)
    • Avoid scratching or rubbing forcefully
  • Chemical Irritants
    • Avoid using irritating chemicals
• Avoid Iatrogenic Factors
  • Examples: Follow standardized treatments, regular follow-ups, and communicate promptly
• Avoid Prolonged Sun Exposure
  • Avoid consuming photosensitive foods
  • Avoid long hours of outdoor work or intense sun exposure
• Dietary Recommendations
  • Encourage consumption of: Spinach, celery
  • Avoid ingestion of photosensitive foods
• Use of Antioxidants
  • Examples: Ascorbic acid (Vitamin C), Alpha-lipoic acid
• Lifestyle Habits
  • Balance work and rest
  • Maintain a relaxed mindset

Prognosis and Patient Education:

1. Avoid all potential triggers and strictly adhere to sun protection before and after treatment.
2. Avoid spicy, irritating foods and photosensitive foods. Maintain sufficient sleep and regulate emotional well-being.

This article mainly introduces chemical peeling and pigmentary lasers (Q-switched and picosecond lasers). In the next session, we’ll discuss intense pulsed light, fractional lasers, and mesotherapy.

Chemical Peeling

Chemical peeling, also known as chemical resurfacing or simply “acid peels,” involves applying different concentrations of acid-based solutions to the skin’s surface, causing controlled damage and harnessing the skin’s wound-healing response to promote remodeling and accelerate pigment metabolism and dermal collagen renewal. Common peeling agents include glycolic acid, salicylic acid, trichloroacetic acid (TCA), mandelic acid (also known as amygdalic acid), and blended acids. Here, it’s important to note that glycolic acid and hydroxyacetic acid are the same.

The consensus did not provide detailed methods for using chemical peels in the treatment of PIH and only specifically addressed salicylic acid. However, it must be noted that chemical peeling is the fastest and most effective method for treating epidermal pigmentation disorders—there’s no other like it. That’s because, in PIH and superficial hyperpigmentation, the melanin is deposited in the epidermis, and superficial chemical peels can remove these layers up to the basal layer. As the pigmented epidermal layers are peeled away, the melanin is removed along with them, resulting in rapid brightening and fading of the pigmentation.

In the Chinese Expert Consensus on the Clinical Application of Chemical Peeling (2022), there’s a comprehensive table listing which acids can be used to treat PIH and the strength of the evidence supporting each method (i.e., how reliable the treatments are).

In the Chinese Expert Consensus on the Clinical Application of Chemical Peeling (2022), it is stated that superficial chemical peels can both promote epidermal renewal and remove epidermal pigment, while also inhibiting tyrosinase activity. In addition, when combined with other topical agents, chemical peeling can enhance drug absorption. However, since chemical peeling itself can also induce PIH, it must be performed with caution, using only superficial peels.

Interpretation:

Superficial chemical peels target only the epidermis and are clearly effective for PIH. Superficial peeling does not damage the basement membrane, preventing epidermal detachment (which would cause the entire epidermis to lift away from the skin). The depth of peeling depends not only on the acid concentration but also closely on the contact time of the acid on the skin.

Using 20–50% glycolic acid for chemical peeling to treat PIH is considered safe, but it requires close monitoring of the skin’s endpoint reaction (erythema). Once erythema appears, the acid should be neutralized immediately—widespread frosting must be avoided.

When using an appropriate concentration of acid, neutralizing it promptly according to the endpoint reaction, and following proper post-peel skincare, well-controlled chemical peels are unlikely to cause further pigmentation issues.

The interval between chemical peels for treating PIH depends mainly on the acid concentration and the treatment reaction. For glycolic acid concentrations of 35% or below, treatments can typically be performed every 2–4 weeks.

Even when using lower acid concentrations, if there is a strong endpoint reaction (such as widespread erythema or significant frosting), it’s essential to extend the interval to at least 4 weeks.

Post-Inflammatory Hyperpigmentation (Cheek)

• Case Presentation:
  Post-inflammatory hyperpigmentation on the right cheek following a burn injury.
• Fitzpatrick Skin Type:
  Тип II
• Glogau Classification:
  Тип i
• Indication:
  Post-inflammatory hyperpigmentation on the right cheek as a sequela of a burn injury.

Зона лечения

• Right cheek

Expected Peeling Grade and Treatment Goals

• Repeated multiple superficial A–B grade peels to stimulate epidermal desquamation and enhance the penetration of brightening agents (e.g., hydroquinone) into the deeper epidermis, while minimizing inflammatory reactions.

Peeling Protocol

• Superficial A grade peels with 20–50% glycolic acid (GA), at 2-week intervals, for a total of 8 sessions.

Pre-peel Treatment During the Peeling Interval

• Daily application of 2% hydroquinone hydrophilic ointment to the right cheek, starting 4 weeks before the first peel, to inhibit tyrosinase activity.
• Retinoic acid is not recommended to avoid skin irritation.

Post-treatment Follow-up and Care

• For 3 months after the last treatment, continue daily application of 2% hydroquinone hydrophilic ointment to the treated area.
• After that, continue topical therapy but gradually taper the frequency: in the subsequent 2 months, apply every other day; reduce to twice weekly before discontinuation.
• During the day, apply a high SPF broad-spectrum sunscreen.

Follow-up Photography Schedule

• 12 weeks after the final treatment.

Photoelectric Therapy (Strong Recommendation): Expert Consensus

The expert consensus points out that photoelectric therapy is a “double-edged sword” in the treatment of PIH—it can trigger or exacerbate PIH lesions if not performed properly. However, with the appropriate wavelength, energy density, and post-treatment care, photoelectric therapy can be highly effective in treating PIH, often surpassing the results of topical and oral treatments. Common photoelectric devices include Q-switched lasers, intense pulsed light (IPL), picosecond lasers, and fractional lasers.

Here are the principles I have summarized for using photoelectric therapy in PIH.

Application Principles for Laser/IPL Treatment of PIH

• Photoelectric treatments should not be used on PIH lesions caused by earlier photoelectric treatments if there is still residual inflammation, as they may worsen PIH in the short term.
• Photoelectric therapy is generally considered a secondary treatment option for PIH.
• Only use photoelectric treatments on stable PIH, not on PIH that still has active inflammation.
• Mixed-type PIH (with both epidermal and dermal pigment deposition) can be treated with photoelectric devices, focusing on the dermal pigment component.
• Persistent PIH can be treated with photoelectric therapy.
• Because the pathogenesis of PIH is similar to that of melasma, the choice of device and treatment parameters for PIH can be guided by protocols used in melasma treatment.

Q-switched Lasers:

Currently, the 1064 nm large-spot, low-energy Q-switched laser is considered the most effective treatment for PIH, making it the first-choice photoelectric therapy for PIH. This treatment approach is also known as laser toning.

The advantages of using the 1064 nm large-spot, low-energy Q-switched laser for PIH включать:

1. The 1064 nm wavelength targets the deeper dermis, with minimal absorption by epidermal melanin, thereby avoiding excessive heat production in melanocytes that could otherwise provoke further pigmentation.
2. The 1064 nm wavelength penetrates deeply, making it effective for treating dermal pigment deposits as well.

Parameter-setting principles:

• А spot size of 6 mm or larger is considered a large spot; spot sizes between 6-10 mm can be selected.
• The darker the pigmentation (the more melanin deposition), the lower the energy used.
• The lighter the pigmentation, the higher the energy that can be safely applied.
• Это should not be used on PIH with residual inflammation (such as visible erythema or other signs of inflammation).
• The 755 nm Q-switched laser can also be used for PIH treatment with a large-spot, low-energy approach.

Important Considerations:

1. When using pigment lasers to treat PIH, it is essential to confirm that melasma is not present, and that melasma is not being misdiagnosed as PIH—this is critical.
   If melasma is present, the use of large-spot, low-energy Q-switched lasers is not recommended.
2. Для confirmed PIH cases without residual inflammation, the recommended конечная реакция is the appearance of pronounced erythema in the pigmented area.

Treatment Course Settings for Q-switched laser treatment for PIH

Many international publications suggest a treatment interval of 1–2 weeks per session.
Principles for setting treatment intervals (for large spot sizes) are as follows:

1. In most cases, a treatment interval of 4 недели is recommended, as the average turnover time for epidermal pigmentation metabolism is 28 days.
2. The rationale for shortening the treatment interval is to enhance efficacy. The endpoint reaction for large-spot, low-energy PIH treatment is the appearance of pronounced erythema. This erythema occurs due to absorption of light and subsequent heating of melanin in the epidermis.
   However, it’s impossible to visually assess whether dermal pigment deposits have been fully affected. Dermal pigmentation is the most challenging to remove. If, within 1–2 weeks after treatment, the skin fully recovers и no excessive epidermal reaction or worsening of pigmentation occurs, increasing treatment frequency can help better target dermal pigment deposits and improve outcomes for epidermal melanin as well.
3. The exact interval should be determined flexibly, based on factors such as:
   • Skin color
   • Pigmentation color (intensity and depth of pigment in the dermis)
   • Immediate post-laser epidermal reaction

Pico Laser for PIH Treatment

Pico lasers also belong to the category of pigment-targeting lasers and can be used with a 1064 nm wavelength in a large-spot, low-energy scanning mode for treating post-inflammatory hyperpigmentation (PIH). The treatment principles, parameter settings, and precautions for pico laser therapy are essentially the same as those for Q-switched lasers.

However, for permanent PIH, a 2022 clinical study led by Professor Huang Lüpíng’s team at the Chinese PLA General Hospital’s Department of Plastic Surgery explored a different approach. They defined permanent PIH as cases with a duration of ≥2 years and found that large-spot, low-energy treatments were less effective for this condition.

To address this, the team investigated using medium-spot (4 mm) и medium-energy (4.0–4.5 J/cm²) Q-switched 1064 nm laser settings to treat permanent PIH. Treatments were administered every 1–2 months, с at least 4 sessions. The treatment endpoint was the appearance of mild pinpoint bleeding.

The results of this study were as follows:

• Average number of sessions: 5.3 ± 2.9
• Complete clearance: 4 patients (27%)
• Significant improvement: 5 patients (30%)
• Good improvement: 2 patients (13%)
• Moderate improvement: 1 patient (6%)
• Little to no improvement: 3 patients (20%)

Overall, 73% of patients achieved more than 50% improvement.

For severe and refractory PIH, especially where the pigment deposition is in the dermis and difficult to remove, higher energy levels are needed to achieve sufficient dermal action. Consequently, the endpoint reaction for permanent PIH treatment is defined as the appearance of mild pinpoint bleeding.

Пикосекундный лазер

The treatment principles of the picosecond laser for PIH are similar to those of the Q-switched laser, typically using a 1064 nm large spot size with medium to low energy. The endpoint reaction is also the same.

Although picosecond lasers have been available for quite some time, current clinical research has not demonstrated that picosecond laser toning treatments outperform Q-switched laser toning in managing PIH. This is because the picosecond laser’s advantage over the Q-switched laser lies primarily in targeted, high-energy spot treatments for pigmented lesions, where its photoacoustic effect is significantly stronger. In toning treatments (large-area scanning), however, the dominant mechanism is photothermal rather than photoacoustic. That said, no studies have shown that picosecond lasers are less effective than Q-switched lasers for this application.

The main advantage of the Q-switched laser is its broader range of adjustable energy densities.

755nm Pigment-Specific Laser

Both the 755nm Q-switched laser (nanosecond) and the picosecond laser can be used to treat PIH.

Based on the absorption spectrum of melanin, it’s clear that melanin absorbs more light at 755nm compared to 1064nm. However, the penetration depth of 755nm lasers in the skin is significantly less than that of 1064nm lasers.

Therefore, for epidermal-type PIH, the 755nm laser has an advantage over the 1064nm laser.
On the other hand, for dermal-type or mixed-type PIH, the treatment effect of the 755nm laser is weaker than that of the 1064nm laser.

The CO₂ fractional laser can also be used as an adjunctive treatment for PIH. The main mechanism of the fractional mode is to promote the elimination of dermal melanin through the epidermis—essentially accelerating the metabolism of the pigment.

The left is 0.4J/cm2, 8mm spot size, intervals 1-2 months, totally 4 times, Picosure Focus

The right is 2.49J/cm2, 3.2mm spot size, intervals 6 months, totally twice, Picosure scanning mode.

In recent years, the concept of subcellular selective photothermolysis has emerged. This involves using low-energy QS lasers that target cellular organelles, such as melanosomes, rather than destroying melanocytes themselves. By focusing on destroying intracellular organelles, this approach helps reduce the risk of complications such as post-inflammatory hyperpigmentation (PIH) and hypopigmentation [69,70]. Weekly low-energy QS Nd:YAG laser treatments (up to 10 sessions) have been successfully employed in treating melasma. Traditional QS Nd:YAG laser treatment is based on the principle of selective photothermolysis, which targets and destroys pigment-containing cells. This destruction triggers inflammation, which can lead to pigmentary complications and recurrence.

In contrast, the high peak power and ultra-short pulse duration (5 ns) of these treatments—combined with a flat-top beam profile—allow them to selectively disrupt melanin within target cells while preserving overall cell viability. This aligns with the proposed mechanism of subcellular selective photothermolysis. Because of the low energy and lack of significant cell death, inflammation and heating are minimized, reducing the risk of recurrence.

Several studies have reported success with low-energy QS Nd:YAG laser treatments (laser toning, or “laser skin toning”), typically performed once a week for a total of 8–10 sessions. Although effective, literature has also documented the risk of mottled hypopigmentation following frequent QS Nd:YAG laser treatments. Therefore, caution is necessary, and patients should be informed of this risk.

A modified laser toning protocol uses low energy with a large spot size (8–10 mm), treating every 2 weeks instead of weekly, for a total of 6–8 sessions. This approach has been shown to lower the risk of hypopigmentation and is considered more favorable. However, studies have also reported a recurrence rate as high as 81% after discontinuation of treatment.

Краткое содержание

1. Minimally invasive treatments such as laser therapy and chemical peels are key strategies for managing PIH.
2. Superficial chemical peels offer the fastest improvement for PIH. It’s recommended to use glycolic acid at low concentrations (≤50%), closely monitor endpoint reactions, and promptly neutralize the acid. These peels exfoliate the epidermis above the basement membrane, making them effective for epidermal PIH but ineffective for dermal PIH, and only partially effective for mixed-type PIH by targeting epidermal pigment.
3. For laser treatment of PIH, the first choice is 1064 nm large spot-size, low-energy Q-switched or picosecond lasers. The recommended endpoint reaction is the appearance of prominent erythema in the treated area. Treatment intervals are usually four weeks, and reducing the interval should be done with caution.
4. For permanent PIH lasting ≥2 years, a medium spot size (4 mm) and medium energy (4.0–4.5 J/cm²) can be used. Treatments are performed every 1–2 months, with at least four sessions. The recommended endpoint reaction is the appearance of mild pinpoint bleeding.
5. When using large spot-size laser toning for PIH, note that repeated treatments can induce melanocyte apoptosis, leading to hypopigmentation or mottled depigmentation. Therefore, individualized parameter settings are crucial for each patient. Avoid pursuing excessive endpoint reactions in any session. Treatment intervals are typically four weeks, with an average total of 5–6 sessions and generally not exceeding 10 treatments (as noted in reference 5). Exceeding 10 sessions significantly increases the risk of permanent hypopigmentation due to melanocyte apoptosis.
6. Because chemical peels are relatively safe for melasma, while pigment lasers can easily exacerbate it, it is critical to ensure no concurrent melasma is present when using 1064 nm large spot-size, low-energy laser toning for PIH (this is extremely important). If there is any uncertainty, pigment laser treatment for PIH should be avoided.