When patients go to the office of a dermatologist or a cosmetic doctor and explain that they have had a laser treatment to remove a spot, to remove hair, or to remove a tattoo, they are not always able to identify the type of laser with which it has been treated. Even if we suggest laser treatment, they don’t know exactly what we’re talking about. They may sense that with the laser we burn or destroy something and, however, laser equipment does not always work this way.
Even if you are not going to become laser expert, it is good to know some guides so that you can distinguish some equipment from others and know the different types of lasers that exist in dermatology. Lasers are tools that emit light. Unlike a light bulb that also emits light, this one is not considered harmful or dangerous. What characterizes a laser equipment is that it emits a large amount of light in a very short period of time, heating surfaces that specifically absorb this light. For example, a red spot on the skin preferentially absorbs green or yellow light, and it is these colors that are used in the laser to eliminate spots of this type. Another fundamental characteristic of lasers is that they emit a single color of light, which makes them specific when it comes to treating, destroying or heating certain objects such as hair, a red or brown spot or a scar.
How to classify lasers?
There are several ways to classify lasers, mainly through the color they emit or the purity of their light, the duration of their shot…
Lasers can be classified as ablative (burning) and non-ablative (heating). An ablative laser is one that, when absorbed by the skin, allows temperatures above 100 °C to be reached and water volatilizes. Continuity in the skin and they basically make holes. This is what we could say “burn”. Non-ablative lasers would be those that, when absorbed by the skin, do not raise its temperature above 100 °C. These lasers are dedicated to heating but not burning. They serve to increase the amount of collagen in the skin. Another way to distinguish lasers is through colors. Green lasers are used to eliminate red spots, such as a small vein, a small red dot or a congenital red spot that we were born with. The best known green laser is the KTP, whose name refers to a crystal that is placed in front of the laser tube to convert its light into green. Another widely used laser is the yellow one. It is also preferably absorbed by red structures, and can be used both to remove tattoos (if the type of laser emits a very short shot and is of the Q switch type), and to treat vascular structures. This type of laser is also known as pulsed dye lasers. We also have red lasers, such as the diode laser or the alexandrite laser, which are used to burn hair from the skin. Red light is used since the hair is dark, and therefore, it is capable of absorbing any type of light. However, this color also has the ability to penetrate the skin better, and reach the roots of the hair more easily.
The color of the diode laser is 800 nm or 810 nm, while the Alexandrite laser uses a wavelength of 755 km. You can imagine that these numbers correspond to the colors that these lasers emit. Above this color are infrared lasers. The best known is the neodymium YAG laser, which has low absorption and great penetration, which allows us to treat deep structures of the skin such as varicose veins. The color of this laser is 1064 m. Other very useful lasers are those that work in the infrared range, such as 1340 nm, 1440 nm or 1540 nm. This light is not very well absorbed by the water in the skin and this allows it to reach quite deep and heat the skin to 60 or 70°C. At these temperatures the skin reacts by forming new collagen, and the sebaceous glands tend to melt and become smaller, making this treatment ideal for treating acne, scars, or rejuvenating the skin. At a longer wavelength, there are two very interesting lasers called Erbium laser and CO2 laser, which are used to destroy small warts, moles, wrinkles or to smooth the skin in case of aging or scars. The Erbium laser emits a wavelength of 2940 nm. With this wavelength, water absorbs light very quickly and heats up so easily that the laser allows us to literally make holes and vaporize the skin. However, since the Erbium laser is very easily absorbed by the water in the skin, it barely has the ability to penetrate, and the wounds created by this type of laser are very superficial, allowing the skin to repair itself quickly.
On the other hand, the CO2 laser is traditionally used, with a wavelength of 10,640 nm. It is not absorbed as much by the water in the skin, and therefore penetrates deeper, so the effect is somewhat greater but the skin repair time is also longer. There is a last type of laser called Excimer laser that emits at the ultraviolet B wavelength, that is, at 308 nm. This is the same color that the Sun uses to induce tanning or the production of melanin or skin pigment. It is used to treat vitiligo and also in inflammatory lesions such as psoriasis or eczema. Another trick to know what type of laser we have in front of us is the size or shape of its shot. In general, lasers give circular shots, while diode lasers give square shots. When we are treated with a laser that is long and rectangular, this is actually an intense pulsed light or IPL. The IPL is a very useful tool and very similar to the laser with which we can do hair removal, reduce the size of the pore, improve the appearance of the skin, stimulate the production of collagen, remove spots, or eliminate redness. It is not strictly speaking a laser since it does not emit a single color, but rather a range of these. I hope that with this summary I have been able to help you better understand the different laser equipment.
