The number of sessions needed to fully remove the hair in a given area varies according to the individual and the area to be targeted. However, its usually requires 4 – 8 sessions, with one session every 5 – 10 weeks.
The characteristics of patients that influence the effectiveness of laser hair removal include hair color; skin tone; hair texture; hair density; hormonal status; and if the patient is on any medication. Laser treatments only target hair in the growing or anagen phase, but hair growth is not a uniform
process, with different batches of hair in different phases of the hair growth cycle. Therefore, successful treatment will require a number of sessions to target each batch of hair as they enter the anagen phase.
Laser hair removal works by targeting the dark melanin pigment found in the hair follicle. The melanin pigment absorbs light energy and converts it into heat, destroying the hair and inhibiting regrowth. Dark hair colors, such as black and dark brown, contain eumelanin, while lighter shades
such as blonde and red hair contain pheomelanin. Eumelanin absorbs more energy than pheomelanin, and consequently, treatments are more effective on patients with darker hair colors, requiring fewer sessions. There are no melanin pigments present in grey and white hair to absorb the light produced by hair removal lasers, and as such, this method is ineffective on these shades of hair color.
However, melanin is not only located in hair but is also found in the skin. Furthermore, the darker a person’s skin is, the more melanin there is to absorb the light energy and convert it to heat, making it harder to avoid damaging the skin’s surface. As such, the laser has to be focused on the target area long enough to heat the hair, but not so long that it heats up and damages the skin. Consequently, hair removal lasers cannot be focussed on an area of dark skin for as long as they can with lighter skin, for fear of causing damage, requiring more sessions to achieve full removal.
The texture and density of a patient’s hair also affect the effectiveness of laser hair removal treatments. Coarse hair is able to absorb more heat energy than fine hair, and so will require fewer sessions to remove all the hair in the desired area, while hair density is simply the number of hair follicles found in a given area. The more hair found in a given area, the more time is needed to successfully treat it.
The number of laser hair removal sessions is also determined by the areas being treated. Treating facial hair will require more frequent sessions than treatments to other parts of the body, as the length of the hair growth cycles is much shorter than that of other areas. Typically, facial treatments are spaced about 5 weeks apart, while leg and back treatments are spaced 8 – 10 weeks apart. It is important to note – especially for older patients – that hormonal changes may stimulate hair regrowth in areas already successfully treated, by triggering the active growth or anagen phase.
These hormonal changes may occur naturally in the body or may be the result of medication or medical procedures.