PIHの審美的治療：色素レーザーと化学的剥離

炎症後色素沈着過剰症 (PIH) 急性または慢性の炎症刺激に伴う過剰な色素沈着を特徴とする皮膚の状態です。 PIH は自己制限的な性質を持っていますが、数か月、場合によっては数年にわたって持続する可能性があり、患者の外観と生活の質に重大な影響を与えます。現在、中国ではPIHの予防と治療に関して統一された標準化されたコンセンサスは存在しない。

このギャップに対応して、中国医師会美容・美容医療支部の皮膚科・美容医療グループは最近、臨床経験と最近の文献に基づいた「炎症後色素沈着過剰症の予防と治療に関する専門家のコンセンサス（2024年版）」を発表した。以下にこの合意の概要を示します。

疫学的特徴:

1. PIHはどの年齢でも発症する可能性があり、男性でも女性でも罹患率は同様です。
2. PIH は一般に、フィッツパトリックの皮膚タイプ IV から VI でより顕著です。東アジア人（中国人を含む）は主にフィッツパトリック皮膚タイプ III および IV に分類されます。
3. PIH は、疾患関連要因、外傷、環境要因、医原性 (医学的) 要因、個人の素因など、さまざまな要因によって引き起こされる可能性があります。ニキビは PIH の最も一般的な原因の 1 つであり、特にフィッツパトリック肌タイプ IV ～ VI の人に当てはまります。

病因:

1. 炎症刺激はケラチノサイトによるエイコサノイドの生成を媒介し、チロシナーゼ活性を増加させ、メラニン合成を促進します。
2. 炎症因子はメラノサイトを刺激し、表皮のメラニン沈着を引き起こします。
3. 炎症攻撃によりメラノサイトが損傷し、メラニン顆粒が表皮から真皮に脱落し、真皮型メラニン沈着が生じます。
4. 炎症は局所的な皮膚の代謝機能障害を引き起こし、メラニン形成のさまざまな段階に影響を与えます。
5. 基底細胞層の炎症後の破壊は、上部真皮メラニンを貪食してメラノファージになる真皮マクロファージの増加により、色素失禁を引き起こす可能性があります。

臨床症状:

1. PIH の典型的な臨床症状は、薄茶色から暗褐色の色素斑であり、体のどの部分にも発生する可能性があります。
2. 組織学的には、PIH は表皮型と真皮型に分類でき、同じ患者に両方の型が観察される場合があります。
3. 表皮型PIHは数か月から数年以内に自然に消失する可能性がありますが、真皮型PIHは消失するまでに数年かかる場合や、永久に持続する場合があります。

治療方法

1️⃣ 外用薬

• 強くお勧めします
  • 阻害する薬 プロピオニバクテリウム・アクネス activity (clindamycin): commonly used concentration 2%–4%, can be used long-term during the maintenance phase.
  • 阻害する薬 プロピオニバクテリウム・アクネス 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).

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2️⃣ Oral Medications

• 強くお勧めします
  • 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.

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3️⃣ ケミカルピーリング (強くお勧めします)

• 主な代理店： グリコール酸、サリチル酸、乳酸、トリクロロ酢酸、マンデル酸、複合酸など
• マイルドピール： 低濃度、短期間、主に閉鎖面皰や皮脂腺の活動亢進による過剰な皮脂分泌に効果があります。
• ミディアム/ディープピール: 初期、中期、後期のニキビに。局所的な抗菌薬と抗感染症薬が必要です。
• 日焼け止め： 紫外線への曝露を避けてください。ホルモン剤を使用する場合は禁忌です。

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4️⃣ 光線療法 (強く推奨)

• Qスイッチレーザー
  • 波長: 1064nm、694nm (大きなスポットサイズ、低エネルギーフラクショナルモード)。
• 強烈なパルスライト（IPL）
  • 波長: 590nm、640nm フィルター (主に色素沈着病変用)。
• ピコセカンドレーザー
  • 適応症: 大きなスポット サイズ、低エネルギー フラクショナル モード (PIH を回避するため)。
• Fractional Laser
  • Wavelengths: non-ablative 1550 nm, 1927 nm (chosen based on skin type, PIH risk, and inflammation degree).

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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.

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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. 辛い食べ物、刺激的な食べ物、光に敏感な食べ物は避けてください。十分な睡眠を維持し、精神的な健康を調整します。

この記事では主にケミカルピーリングと色素レーザー（Qスイッチレーザーやピコ秒レーザー）について紹介します。次回のセッションでは、強力なパルスライト、フラクショナルレーザー、メソセラピーについて説明します。

ケミカルピーリング

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.

ケミカルピーリングの臨床応用に関する中国の専門家コンセンサス（2022年）には、PIHの治療にどの酸を使用できるか、および各方法を裏付ける証拠の強さ（つまり、治療法がどの程度信頼できるか）をリストした包括的な表があります。

で ケミカルピーリングの臨床応用に関する中国専門家のコンセンサス（2022年）、表面ケミカルピーリングは、表皮の再生を促進し、表皮色素を除去すると同時に、チロシナーゼ活性を阻害することができると述べられています。さらに、ケミカルピーリングを他の外用剤と組み合わせると、薬物の吸収を高めることができます。ただし、ケミカルピーリング自体もPIHを誘発する可能性があるため、表面的なピーリングのみを使用し、慎重に行う必要があります。

解釈:

表面ケミカルピーリングは表皮のみを対象とし、PIHに対して明らかに効果があります。表面剥離は基底膜を損傷せず、表皮剥離（表皮全体が皮膚から剥がれてしまいます）を防ぎます。ピーリングの深さは酸の濃度だけでなく、酸が皮膚に接触する時間にも大きく依存します。

使用する 20 ～ 50% グリコール酸 PIHを治療するためのケミカルピーリングは安全であると考えられていますが、皮膚の終点反応（紅斑）を注意深く監視する必要があります。紅斑が現れたら、直ちに酸を中和する必要があります。広範囲にわたるフロスティングは避けなければなりません。

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 少なくとも4週間。

Post-Inflammatory Hyperpigmentation (Cheek)

• Case Presentation:
  Post-inflammatory hyperpigmentation on the right cheek following a burn injury.
• フィッツパトリックの肌タイプ:
  タイプII
• グロガウ分類:
  タイプI
• 表示:
  火傷の後遺症としての右頬の炎症後色素沈着過剰。

治療エリア

• 右頬

期待されるピーリンググレードと治療目標

• 表皮の A ～ B グレードのピーリングを複数回繰り返して、表皮の落屑を刺激し、炎症反応を最小限に抑えながら、より深い表皮への美白剤 (ハイドロキノンなど) の浸透を高めます。

ピーリングプロトコル

• 20 ～ 50% のグリコール酸 (GA) を使用した表面 A グレードのピーリングを 2 週間間隔で、合計 8 回行います。

ピーリング間隔中のプレピーリング治療

• チロシナーゼ活性を阻害するために、最初の皮むきの 4 週間前から右頬に 2% ハイドロキノン親水性軟膏を毎日塗布します。
• 皮膚の炎症を避けるために、レチノイン酸は推奨されません。

治療後のフォローアップとケア

• 最後の治療後3か月間は、2%ハイドロキノン親水性軟膏を治療部位に毎日塗布し続けてください。
• その後、局所治療を続けますが、徐々に頻度を減らしていきます。次の 2 か月間は 1 日おきに塗布します。中止する前に週2回に減らしてください。
• 日中は、SPF の高い広域スペクトルの日焼け止めを塗りましょう。

フォローアップ撮影スケジュール

• 最終治療から12週間後。

光電療法 (強く推奨): 専門家のコンセンサス

専門家のコンセンサスは次のように指摘しています。 光電療法 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。

の PIH に 1064 nm 大スポット、低エネルギー Q スイッチ レーザーを使用する利点 含む：

1. 1064nmの波長は真皮の深部にアプローチします表皮メラニンによる吸収を最小限に抑え、さらなる色素沈着を引き起こす可能性のあるメラノサイトでの過剰な熱生成を回避します。
2. 1064nmの波長が深く浸透します、真皮色素沈着の治療にも効果的です。

パラメータ設定の原則:

• あ スポットサイズ6mm以上 大きなスポットとみなされます。間のスポットサイズ 6～10mm を選択することができます。
• 色素沈着が濃いほど（メラニンの沈着が多いほど）、使用されるエネルギーは少なくなります。。
• 色素沈着が明るいほど、安全に適用できるエネルギーが高くなります。
• それ 炎症が残っているPIHには使用しないでください (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. のために confirmed PIH cases without residual inflammation, the recommended endpoint reaction 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週間 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 そして 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. の 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) そして 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、 と 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%)

全体、 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.

ピコセカンドレーザー

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.

まとめ

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.