The laser is the acronym for Light Amplification by Stimulated Emission of Radiation; It has been used for decades in dermatology and plastic surgery, it has more and more applications in these specialties.
A laser is a device that is capable of generating a beam of collimated light (unidirectional, where each ray of light is considered parallel to the others), monochromatic (with a single wavelength of a single color), and coherent (all waves are coupled in length, amplitude and number, all being in the same phase of time and space)
All patients require a consultation before the start of treatment, for a complete medical evaluation in which the skin phototype is classified according to Fitzpatrick. The patient’s expectations should be evaluated, take pictures before the start of treatment; explain the possible risks: scar, blistering, ulcers, folliculitis, acne, hyperpigmentation or hypopigmentation, recurrence or poor response to treatment and informed consent must be signed.
Relative contraindications: history of keloids or hypertrophic scars. Absolute contraindications: ingestion of photosensitizing drugs, taking of isotretinoin in the last six months, lupus erythematosus, history of diseases with Koebner’s phenomenon, pregnancy (although there is no evidence of injury to the fetus so far). Patients with a history of herpes near the procedure site should receive prophylaxis 24 hours before and seven days later. You should not have sun exposure the previous four weeks, or during the duration of the treatment, and you should recommend the daily use of sunscreen.
Waxing It is used for cosmetic purposes and diseases such as keloid acne of the back of the neck, folliculitis decalvans and pseudo-folliculitis of the beard. In hair removal, the chromophore sought is the melanin of the hair shaft, the external root sheath and the hair follicle matrix, which is reached with wavelengths of 600 to 1,100 nm that are selective for their dermal penetration.
However, epidermal melanin can compete in absorption and cause pigmentation disorders; for this reason, thermal relaxation times less than or equal to those of the hair follicle (10-100 ms, depending on the diameter) should be used and, also, it should be taken into account that firing can produce peripheral heating.
There are three means by which the laser destroys the hair follicles: by photothermal damaged by heat, which is the main mechanism of action; by photomechanical damage with damage from the generation of shock waves, and by photochemical damage from the generation of toxic mediators such as oxygen-free radicals. The follicles in anagen phase are in the superficial dermis with an active division, which makes them more vulnerable.
To increase the rate of improvement it is recommended that the patient be waxed eight weeks before the procedure, to increase the percentage of follicles in the anagen phase. Areas with thin hairs should be treated very carefully, because sublethal doses have been reported to induce the growth of terminal hairs. Laser hair removal is less effective in hairs that are not very dark, so Food and Drug.
Unwanted effects with laser hair removal Short-term effects have been reported: pain, peripheral edema in the first 48 hours, blister, peripheral crust, purpura, and cold urticaria. Transient effects (duration of weeks to months) are hyperpigmentation or hypopigmentation. The persistent effects are hyperpigmentation, hypopigmentation, scar, and atrophy. Pigmentary changes occur more frequently in phototypes greater than IV,
Photoaging Non-ablative rejuvenation: it is produced by the action of controlled heat in the dermis, without epidermal damage, with the formation of new collagen that replaces the damaged one by sunlight. It has been classified arbitrarily in type 1, with an improvement of pigmentary changes, pilosebaceous and vessels, and in type 2, with reduction of light to moderate wrinkles or dermal components. In the first, melanin and hemoglobin are sought as chromophores and in the second, water is also used. Look for wavelengths in the infrared range (1,000 to 1,500 nm) with little absorption in surface tissues that contain water and deep tissue penetration.
IPL: it is absorbed by the dermal vessels, with the release of inflammatory mediators that increase fibroblastic activity and collagen production. Handpieces are used.
Absolute contraindications for laser rejuvenation:
Scars and keloids Scars are of various types. The hypertrophic show abnormal proliferation of collagen limited to the area of epithelial damage during the wound remodeling phase, they can be red, nodular with keloid or involution evolution. Keloids, on the other hand, are scars that go beyond the limits of initial skin damage. Besides, the scars can be atrophic or pigmented.
The IP laser is currently considered a first-line treatment in hypertrophic scars and keloids. Its mechanism of action is not clear; It is believed to induce tissue hypoxia, which leads to catabolism and decreased cellular function, with impaired collagen disulfide bridges that leads to rearrangement of its fibers39. The reported improvement rates are between 57 and 83%, with fluences of 5 to 7 J / cm2 and intervals between sessions of six to eight weeks. The improvement is greater in hypertrophic scars than in keloids.
Laser and acne It is a common disorder and four main factors contribute to its formation: P. acnes, increased sebum production, follicular hyperkeratinization, and follicular inflammation. Propionibacterium acnes produces endogenous chromophores called porphyrins, as part of its metabolic process; these have wavelength absorption between 400 and 700 nm, with a phototoxic effect on the microorganism. Fractional photothermolysis has been used for depressed acne scars, with good therapeutic results in a few sessions.