Permanent hair removal using diode laser or intense pulsed light devices is a technology that has evolved rapidly since its introduction in the late 1980s and FDA approval in 1996. Today, such devices are widely used in dermatology and aesthetic medicine practices, and there is an increasing demand for permanent hair removal procedures. With the development of long-wavelength laser devices, it is now possible to safely treat all skin types.
What does permanent hair removal mean?
Diode Laser or IPL hair removal consists of two different concepts:
1. Temporary hair removal
2. Permanent hair removal
Temporary hair removal refers to a delay in hair regrowth and can last up to 3 months, depending on which stage of the hair follicle cycle the hair being treated is in.
In contrast, permanent hair removal is defined as a significant reduction in the number of hairs following hair removal treatment that is stable for longer than a complete hair follicle cycle (4-12 months).
Laser or IPL hair removal results in initial complete and temporary hair removal for 3 months after treatment, followed by partial permanent hair removal. Therefore, this treatment is effective in reducing the total number of hairs in the long term, while the remaining hair becomes thinner, lighter, and grows more slowly.
Hair Growth Cycle
There are 3 phases:
1. Anagen, or active hair growth phase
2. Catagen phase, or transition regression phase
3. Telogen, or resting phase (also called shedding phase)
During the anagen phase, cells at the root of the hair divide rapidly, causing the hair shaft to grow. During this phase, the amount of melanin in the bulb, which already exceeds the concentration in the skin, increases further.
The catagen phase is a short transition phase during which the hair falls off from the substructure of the papilla and in turn enters a shrinkage process, stopping the production of melanin and starting apoptosis (programmed cell death) of the follicular melanocytes, reaching a change of 1/6th of its original size compared to the anagen phase. During this phase, the blood supply to the hair strand is cut off as it detaches from the papilla, and although it no longer grows, its length increases due to being pushed to the surface of the skin.
Finally, during the telogen phase, the hair follicle is almost completely inactive and the keratinized dead hair remains attached to the body. At the end of this phase, the hair falls off completely from the skin and the follicle restarts the cycle into the anagen phase.
The duration of all these phases is variable and influenced by many variables such as genetics, body part and environmental factors. Generally speaking, the growth phase for body hair is 3-6 months, while that for the scalp is 3-7 years. The degradation phase is 10 days to 3 months. Finally, the resting phase lasts about 3 months.
All these phases are not synchronized, which is why we don’t get temporarily bald or hairless in our lifetime: At every moment, about 80-90% of the hair is in the growth phase or active growth phase, 1-2% in the degradation phase or regression phase, and about 10-15% in the resting phase or resting phase.
Diode VS IPL
There are 6 main differences between different types of permanent hair removal devices:
1. The wavelength of the device
2. The power of the device, which refers to the amount of energy released per time unit
3. The size of the area treated, i.e. the spot size, which varies between a few millimeters to a few centimeters.
4. The pulse duration, which is the time the tissue is exposed to the light energy source
5. The frequency, which is the ratio between power and area (spot size)
6. The surface cooling system.
In general, diode lasers and alexandrite lasers are the most effective, followed by IPL lasers and Nd:YAG lasers.
Diode lasers can be used safely on skin phototypes I-IV.
Alexandrite lasers can be used on skin phototypes I-IV and produce better results on fine hair than diode lasers, but its use is more suitable for lighter skin tones.
Nd:YAG lasers have a larger wavelength than previous devices and therefore have a lower affinity for melanin. For this reason, although the results are not as good, they are safer to use on skin types V-VI and can produce positive results.
Intense pulsed light (IPL) works slightly differently: lasers emit a beam of light at a single wavelength, all in the same direction; IPL devices use a broad-spectrum lamp controlled by a computer, with filters placed in front of it to select the desired wavelength. Also, the light from an IPL device can diverge in all directions, and it is only through the use of a reflective surface that it can be focused into a narrow area. Because IPL has a lower skin penetration ability, it is safer on low-skinned photo types. Because of its broad spectrum, it can also be used on light-colored hair, although the results will be less ideal compared to its use on darker hair.
