755nm wavelength is preferentially absorbed by melanin in hair follicles

755nm laser (commonly used in alexandrite laser or Alexandrite laser) is widely used in the field of medical beauty for a variety of treatments due to its specific wavelength and melanin absorption characteristics, especially for pigmented lesions and hair removal. The following are its main applications and principles:

1. Laser hair removal (most commonly used)

Principle: 755nm wavelength is preferentially absorbed by melanin in hair follicles, generating heat to destroy hair follicle stem cells and inhibit hair regeneration.

Advantages:
Suitable for people with lighter skin (Fitzpatrick I-III type) and thicker and darker hair.

It is more targeted to melanin than 810nm diode laser and has higher hair removal efficiency.

Course of treatment: usually 4-6 times, 4-8 weeks apart.

2. Treatment of pigmented lesions

Indications:
Freckles/sun spots: selective photothermal decomposition of epidermal melanin.

Café de Chine: multiple treatments are required, with a high recurrence rate.

Nevus of Ota (dermal pigment): 755nm can penetrate into the dermis, and treatment can be improved in multiple times.
Tattoo Removal: Especially effective for green and black inks (need to be used with Q-switched mode).
Note: Be cautious with dark skin (IV-VI types), as it may cause pigmentation.

3. Skin rejuvenation and skin reconstruction
Application:
Non-ablative skin rejuvenation: Low-energy 755nm can stimulate collagen proliferation and improve fine lines and pores.
Combined treatment: Combined with 1064nm laser (such as Picosure) to achieve layered skin rejuvenation.

4. Other treatments
Hirsutism (such as PCOS patients): Manage hormonal hair growth through long-term hair removal.
Hidradenitis suppurativa: Reduce hair follicle blockage and inflammation.

Differences in technical modes
Mode Features Application
Long pulse (ms level) Gentle heating, protecting the epidermis Hair removal, vascular lesions (such as leg veins)
Q switch (ns level) High energy short pulse, blasting pigment particles Tattoo, dermal pigment lesions
Picosecond mode Shorter pulse, reducing thermal damage (such as Picosure) Tattoo, pigment + skin rejuvenation combination

Precautions
Before surgery: avoid sun exposure/tanning, stop using photosensitive drugs (such as retinoic acid).
Postoperative: Strictly protect from the sun and avoid high temperature stimulation (such as hot baths).
Contraindications: Active herpes, pregnancy, and scar constitution should be used with caution.

The safety of 755nm laser is relatively high, but the effect is closely related to the operator's experience and equipment parameters (energy, pulse width). It is recommended to choose a regular medical institution for evaluation.