Common knowledge of picosecond laser science.

1. Indications and non-indications for laser treatment of pigmented lesions: Indications: nevus of Ota, nevus Ito, freckles, age spots or sun spots, coffee spots, tattoos, eyebrow tattoos, eyeliner tattoos, lip tattoos, brown spots/moles, Chloasma, pigmentation caused by inflammation or trauma, etc.; non-indications: those who cannot tolerate surgery.

2. The principle of laser treatment of pigmented lesions: Laser treatment of pigmented lesions is based on the principle of selective photothermolysis, that is, the laser energy is absorbed by the pigment particles (melanin bodies, tattoo ink) in the lesion in a very short time (10ns). Absorption generates extremely high temperature (300°C), causing it to expand rapidly, forming micro-bursts, gasification, crushing into very small particles, and then being phagocytized and cleared by macrophages in the tissue.

3. Laser treatment of pigmented lesions is only mildly painful: it feels like a rubber band flicking the skin during treatment, and generally no anesthesia is required. Local infiltration anesthesia, topical anesthesia, or general anesthesia may be used as appropriate for sensitive areas (such as around the eyes), large areas, and infants.

4. Laser treatment of pigmented lesions will not cause irreversible damage to the body: laser will not cause damage to normal tissues of the human body or only cause slight reversible damage, while it will cause irreversible damage to diseased tissues, showing a high degree of selectivity. Scarring can form. The penetration depth of the laser is limited, generally it can only reach the dermis, and will not cause damage to deep tissues. As long as you avoid looking directly at the laser beam, it will not affect your vision. During the treatment of the eye area, the doctor will take certain measures to ensure nothing goes wrong. Laser is not a ray and will not cause radiation damage to the body. Even if the skin is sensitive, it is rare to have an allergic reaction to the laser. Normal eyebrows and eyelashes can still grow after laser tattoo removal.

5. Age of laser treatment: Laser treatment is suitable for patients of any age. In general, the younger the age, the thinner the skin, the shallower the lesions, the stronger the repair and absorption capacity, the fewer the treatment times, and the better the treatment effect. Younger age often requires general anesthesia, which does not affect intelligence, but increases the risk and cost of treatment.

6. Frequency of laser treatment: Laser treatment of pigmented lesions often requires multiple treatments. Ota nevus, livedo/nevus, and tattoos generally need about 5 treatments, coffee spots, eyebrow tattoos and eyeliner need 1 to 3 treatments, and freckles and age spots usually need only one treatment. The interval between each treatment is about 2 months.

7. Reaction and precautions after laser treatment: After laser treatment, mild redness and swelling appear locally, and some blisters appear, which disappear within 2 to 3 days and form scabs. The scabs usually fall off within a week, and the new skin is slightly pink. It takes about 1 to 6 months to recover. The treatment area should be protected from water within 3 days after the operation. Vigorous activities and make-up should not be done before the scab falls off, and the scab should not be forcibly torn off. There are no special dietary requirements. After the scabs fall off, pay attention to sun protection and apply sunscreen. Pigmentation may appear in some patients, and it usually disappears within a few months. Patients with scar constitution may experience excessive scar hyperplasia.