Treating brown spots and freckles with a dual-wavelength picosecond laser combination

1. Mechanism of pigmentation formation

Skin color is influenced by several pigments, including melanin, carotene, and hemoglobin. Pigments are produced by cells called melanocytes, which are distributed throughout the basal layer of the epidermis.

tan-nhang — The distribution and activity of melanin determine skin color. An imbalance can lead to uneven hyperpigmentation.

Pigment production takes place in melanosomes, intracellular organelles within melanocytes. Pigmented lesions result from increased melanin production, excessive melanin deposition in melanosomes, or an increased density of active melanocytes.

2. Classification of pigmented lesions

Pigmented lesions are classified according to their pathogenesis, histopathological characteristics, and the layer of the skin in which melanin is deposited (the depth of pigmentation). The depth of excess melanin in pigmented lesions directly influences the choice of treatment.

For example, when treating pigmentation with lasers, different wavelengths penetrate to different depths within the tissue. Therefore, for laser treatment, pigmented lesions are best classified according to the depth of melanin accumulation in the skin: epidermal, dermal, or mixed pigmentation.

The depth of lesions can be assessed using:

Dermoscopy.
Skin examination.
Visual inspection.

Color can provide an initial indication of the location of a lesion, helping guide treatment selection and prognosis. For example, nearly black Ota nevi may respond more quickly to treatment, whereas blue lesions may take longer.

Upscale hình (2) 2 — The color of a skin lesion is not merely a cosmetic concern; it can also indicate the depth of pigmentation, helping guide appropriate treatment selection and prognosis.

3. Clinical assessment of pigmentation depth based on lesion color

The relationship between color, histopathological location, and pigment quantity is as follows:

Type I: A small amount of pigment located superficially in the epidermis, appearing brown.
Type II: A large amount of pigment located superficially in the epidermis, appearing black.
Type III: A moderate to large amount of pigment in the dermis, appearing blue-gray.

4. Brown spots and freckles

Freckles (ephelides) and brown spots (lentigines) are both common benign hyperpigmented lesions in Caucasian and Asian populations.

Ephelides (freckles): These are hyperpigmented macules measuring 1–2 mm in diameter, although they may be larger. Their color ranges from red to light brown. They are commonly seen in individuals with fair skin, first appearing at 2–3 years of age and increasing in number during adolescence. They often partially fade with age. Freckles are most commonly found on the face, arms, neck, and chest, and become more prominent in summer.
Lentigines (brown spots, SL): These are larger than ephelides, ranging from a few millimeters to several centimeters in diameter, and are dark brown. They are common in people aged 50 years and older and occur on areas of skin frequently exposed to sunlight. Their color is generally unaffected by seasonal changes or the frequency of sun exposure.

In Asia, freckles and brown spots are often regarded as cosmetic concerns that should be removed, whereas in Western cultures, freckles are considered fashionable and are rarely treated for removal. Clinically, freckles and brown spots are not always clearly distinguished, leading to inconsistencies in the terminology used.

5. Histological characteristics of freckles and brown spots

Freckles: Increased melanin, increased melanosome number and size, and elongation and thickening of the epidermal rete ridges.

Brown spots: Proliferation of melanocytes, increased melanin, and elongation of the epidermal rete ridges. Sometimes, the number of melanocytes does not increase, but their melanin-producing activity is enhanced. Brown spots are associated with inflammatory reactions and scattered inflammatory cell deposits in the dermis.

Recent studies have shown that skin with brown spots and severe, chronic sun damage exhibits the following histological changes:

A reduced number of Langerhans cells in the epidermis.
Reduced epidermal thickness and a lower epidermal elasticity score.
Accumulation of senescent fibroblasts.
Inflammatory cell infiltration, clinically manifested as erythema.

These factors help predict persistent brown spots that are difficult to treat and an increased risk of post-inflammatory hyperpigmentation (PIH) following laser treatment. Inflammatory brown spots have lower treatment response rates and a higher risk of PIH after laser treatment than non-inflammatory brown spots. Research suggests that clinicians considering laser treatment for patients with brown spots should perform dermoscopic examination before treatment.

6. Clinical prediction of post-inflammatory hyperpigmentation (PIH) when treating brown spots and freckles with lasers

Upscale hình (3 — *Treatment of brown spots alone using a combination of 532 nm and 1064 nm picosecond laser wavelengths achieved a reported 100% reduction in brown spots after just one treatment session.*

Before performing laser treatment for freckles or brown spots, patients should undergo a thorough examination and consultation. Individuals at increased risk of developing PIH after laser treatment for brown spots and freckles include:

People with darker skin, classified as Fitzpatrick skin types IV and V.
People whose knuckle skin is darker than the surrounding skin.
Patients with a history of PIH, such as persistent post-acne marks, prolonged darkening after trauma, or hyperpigmentation following other invasive procedures.

Brown spots or freckles surrounded by erythema are also associated with a higher risk of PIH than lesions without erythema. Pigmentary disorders such as melasma, freckles, and mottled pigmentation associated with photoaging are significantly associated with PIH. Furthermore, PIH occurs more frequently in individuals with barely visible pores and smooth skin.

7. Current treatments for brown spots and freckles

Commonly used treatments for brown spots and freckles include:

Laser and light-based treatments.
Topical medications that inhibit hyperpigmentation and brighten the skin.
Cryotherapy.
Chemical peels.
Combination therapy.

Among these options:

Combination therapies are considered the most effective treatments for freckles and brown spots. However, they carry a relatively high risk of adverse effects, reported in two-thirds of patients, including nausea, erythema, and blisters, as well as PIH.
Laser and light-based treatments are effective standalone options for freckles and brown spots and are generally well tolerated, with adverse effects reported in approximately one-fifth of patients. Common adverse effects include PIH, hypopigmentation, erythema, and scarring.

Across different laser and light-based treatments for freckles and brown spots, reported efficacy is relatively high, ranging from 75% to 93%. The rate of PIH depends on the type of laser or light source, the selection of treatment parameters, and how these parameters are adjusted.

8. Factors affecting laser treatment for brown spots and freckles

Laser treatment outcomes depend on several factors:

Skin type, PIH risk, and the degree of improvement achievable in each individual patient.
The available laser system: Appropriate selection and adjustment of treatment parameters are crucial in determining treatment efficacy.
The physician’s expertise: The treating physician must understand the pathophysiology of the condition and be proficient in operating and using laser and light-based devices.

9. Treating freckles and brown spots with a dual-wavelength picosecond laser (PS) at 1064 nm and 532 nm

Like earlier nanosecond laser systems, picosecond (PS) lasers have demonstrated excellent efficacy in removing brown spots. Treating brown spots in patients with darker skin using nanosecond lasers carries a relatively high risk of PIH, approximately 25%–47%. The reported rate of PIH after treatment of brown spots with PS lasers ranges from 5% to 10%, depending on the clinical experience of the researchers.

Upscale hình (4 — Brown spots on a background of hyperpigmented skin, with varying pigmentation depths and advanced skin aging. Combined treatment using 532 nm and 1064 nm PS laser wavelengths achieved an 80%–90% reduction in brown spots after three sessions, improved pigmentation at different depths, improved signs of skin aging, and reduced wrinkles.

Compared with the 532 nm Q-switched (QS) laser, treatment of freckles and brown spots with a 532 nm PS laser offers several notable advantages:

A reported 75%–100% improvement in lesions after a single treatment session.
Reduced risk of damage to the basement membrane. The treatment requires substantially lower energy levels to produce an effect in skin tissue, potentially reducing post-laser complications such as PIH and post-inflammatory hypopigmentation.

10. Advantages of combining 532 nm and 1064 nm PS laser wavelengths

Targets different levels of pigmentation in the skin, supporting treatment of advanced photoaging and skin damage associated with pigmentation at varying depths.
Addresses skin aging by increasing epidermal thickness, reducing senescent fibroblasts, and supporting the treatment of treatment-resistant brown spots and freckles in severely photoaged skin.
Uses a photomechanical effect, including laser-induced optical breakdown (LIOB) at the plasma site, to reduce damage to surrounding tissues and minimize adverse effects during laser treatment.

In conclusion, brown spots and freckles are benign forms of superficial hyperpigmentation. They are associated with long-term ultraviolet (UV) exposure and skin aging. Combining 1064 nm and 532 nm picosecond laser wavelengths targets multiple contributing factors and may help treat resistant brown spots. Effective treatment requires an assessment of the patient’s skin condition, an appropriate understanding and adjustment of the available laser parameters, and a treating physician with the necessary expertise and experience.

The information above is for reference purposes only and is not intended as medical advice. Please contact your doctor for detailed medical consultation.