There have been increased inquiries for hair removal. This could be simply because summer is coming up, but there seems to be an increase in interest in hair removal due to the emergence of various treatments to remove face and body hair.
Multiple choices exist to remove hair, including shaving and waxing. Despite the various options, many people still choose laser hair removal with expectations for permanent removal of hair.
However, permanent hair removal is not a correct term. To understand better, you should look into what exactly laser hair removal is. If you understand the principle of laser hair removal, you can also understand the reasons behind the side effects of laser hair removal.
At the early stage of laser hair removal used QSNY(Q-switched Nd:YAG) laser, which is often called pigment laser, to transfer light into kinetic energy and damage the human dermal papilla. Some patients who often receive toning using the QSNY laser barely have vellus hair.
Recently, the QSNY laser is not used alone for hair removal treatment. Thermal relaxation time, the time that hair holds the heat before releasing it, is known to be 40~100 milliseconds. The QSNY laser is inferior to the other types of lasers with longer duration when used for hair removal because of its short duration time of nanoseconds. Thus, lasers with longer duration time that have milliseconds are used frequently in current laser hair removal treatment.
These hair removing lasers with longer duration target melanin in the hair. They employ selective photothermolysis, which uses a laser wavelength with more selective colors, to transfer light to heat. The increased heat from melanin included in the hard keratin of hair destroys the nearby dermal papilla-containing stem cells. This is the basic principle of laser hair removal.
This principle, extended selective photothermolysis, has a target of treatment different from a target of the laser. In other words, hair without melanin or gray hair doesn’t react to the laser. Photodynamic therapy is used to remove that hair but is less effective than removing black hair.
Every hair goes through a growth cycle including three steps: anagen(growth phase), catagen(transition phase), and telogen(resting phase). The hair in anagen is known to be removed most effectively because it exists closest to the dermal papilla. Transplanted hair after hair transplantation doesn’t remain forever after transplanted. The hair is lost once after it enters telogen, and new hair in its anagen grows again and remains.
Just as the stimulus from the hair transplantation makes the telogen hair loss, so does the stimulus from the laser. The hair loses 3~6 weeks after the laser treatment when it enters telogen and regrows as it goes through anagen. Therefore, laser treatment is usually required every 3~6 weeks and targets the hair entering its anagen.
The laser hair removal doesn’t make hair disappear at once. The hair seems to disappear as its thickness and density decrease. In the case of a beard, shaving becomes easier and experiences fewer injuries.
Then, where did the word "permanent hair removal" start from?
When you repeat laser hair removal several times, you only need to retouch once or twice a year. This is the state called ‘permanent hair removal.’ However, vellus hair remains after the laser hair removal even though it can remove grown hair as we can observe the intake of hair loss medication makes the remaining vellus hair into the grown hair. The vellus hair can become the grown hair when it receives a specific stimulus. Based on these facts, we can conclude that laser treatment cannot completely remove the hair.
The second reason to choose laser hair removal is the belief that laser treatment will be safe. However, laser hair removal is not completely safe.
Laser lights up a target to create kinetic or heat energy. The target of laser hair removal, dermal papilla, is located 3~7mm below the surface of the skin. Thus, side effects may occur while the light travels a long way from outside of the skin.
For example, people with darker skin tone whose epidermis has more melanin than others may experience burns before the laser reaches the dermal papilla because it heats up the epidermal melanin. For the same reason, people considering tanning should remove their hair first to decrease the chance of getting burned while tanning. In other words, regions that don’t see sunlight often are less likely to get burned and experience pain.
The laser treatment may cause folliculitis when it is irradiated to thick or dense hair because of the more heat generated. Moreover, people of color are likely to experience post-inflammatory hyperpigmentation, which is a darkening of the skin tone due to laser stimulation. In summary, patients may experience worse pain and temporary side effects if their skin tone is dark or have thick or dense hair. For those cases, longer but safer treatment is recommended to have a better result than a single powerful treatment.
