There are may preconceived ideas about laser hair removal out there. Most of them are myths that we busted already. Some others may be slightly true. People think laser hair removal is a long process. While they usually think that about laser hair removal sessions, which can last as little as ten minutes, it actually is true of the whole laser treatment itself. Industry standards set the minimum number of sessions to six while people usually will need between eight and twelve.
Although we will also answer the question as per why you need multiple laser hair removal sessions, we also want you to know why a laser treatment takes "so much time". Mostly because you will need to wait six weeks between each session. But then, why do you need to wait that long before your next laser hair removal session?
How long do I need to wait between laser hair removal sessions?
1. How does laser hair removal work?
Laser hair removal is a treatment that uses selective photothermolysis. The laser machine will create a beam of light targeting a specific light-absorbing objects without damaging the surrounding skin tissues. This can be achieved thanks to using a specific wavelength and pulse duration. During a laser hair removal session, the beam of light or laser will target the pigments in the hair.
Once the energy is absorbed by the hair, it will travel all the way down to the hair follicle where it will turn into thermal energy. Then, the heat will damage the hair follicle preventing it from producing any more hair. In other words, the laser will cauterize the blood vessel feeding the follicle. If it does not have fuel, it cannot function.
The follicle must be damaged enough to ensure it will not regenerate. Some follicles may need more than one session to be fully out of order. Since the laser targets pigments, it works better on dark hair. Light skin will also produce a sharp contract between skin melanin and hair pigment, ensuring the laser targets only the pigment in the hair.
However, improvement in laser technology such as Nd:YAG lasers allow people of color and people with fair hair to undergo laser hair removal as well. One session of laser hair removal will target between 18% and 20% of all body hair on the targeted area. This is due to the hair growth cycle.
2. What is the hair growth cycle?
Ideally, one session of laser hair removal would target every single body hair on the target area and that would be it. Then, touch up sessions would only be required to ensure more resistant follicles are forever damaged and unable to produce new hair. However, the hair growth cycle makes that impossible.
Body hairs grow in three stages: anagen, catagen and telogen. The anagen phase of growth is the only time when the hair connects to the hair follicle. Thus, it is the only time the laser can travel through to its target and damage it. If the hair root and follicle do not touch, then the energy cannot get to its destination. Thus, laser hair removal only works when the hair is the anagen phase. It is also the time of growth where your hair is the richest in melanin, making it easier to target.
The hair can stay up to six years in the anagen phase of growth. Unfortunately, only 20% of all your body hair (or of all hair on the target area) will be in the anagen phase at any point in time. This explains why one session will be able to remove up to 20% of hair. The thing is, it is close to impossible to know which hair precisely is in the anagen phase of growth and how long it's been in it. Thus, it is also impossible to say which hair follicle was removed and which was not.
3. How many sessions will be required?
The number of laser hair removal sessions a patient will need depends on many factors: age, genetics, medical issues, prescribed medication being taken, and hormonal factors. If you are about to start your first laser hair removal treatment, you are eligible for a free consultation with a laser technician who will be able to assess roughly how many sessions you will need.
People who have been waxing for years may need less sessions. Indeed, even though waxing is not a permanent hair removal method, it impacts long-term growth. After years and years, waxing damages the hair follicle and people will notice less hair. Regardless of past hair removal experience, some people will need just six sessions for a particular area while other may need more.
Although laser hair removal works on dark skins and fair hair, they are still more difficult to target. Thus, it is possible that they may require more sessions. Hormonal areas such as the face and bikini will also require more laser hair removal sessions than non-hormonal areas like the legs. It is common that after 3 to 4 sessions, at least 50% of the hair has been treated and removed.
Since 20% of body hair is targeted during each session, and depending on each patient's hair growth cycle, they may also need more or less laser hair removal sessions.
4. How long should I wait between laser hair removal sessions?
There are several reasons why you need to wait between laser hair removal sessions. The first one is that you need to let your skin rest and regenerate after a laser treatment. Indeed, UV rays are quite aggressive to the skin and too much of it could lead to skin damage.
The second reason is follicle regeneration. Indeed, some follicles will be more resistant than other to laser. Thus, they may need more than one session to be irreversibly damaged. When a hair follicle is not completely out of service, it will regenerate and be able to grow new hair again. Repetitively targeting resistant follicles will not leave them enough time to regenerate.
The third reason is of course the hair growth cycle that is different for each patient, for each area of the body and for each body hair as well. A hair can be in the anagen phase of growth for up to six years. However, how do we know which hair is in which stage and for how long it's been in that particular stage? It's impossible to know.
Waiting six weeks between laser hair removal sessions gives time to body hairs that were not in the anagen phase to enter it. Again, since 20% of hair is in the right stage at any point of time, some will leave it while other will enter it as you go for your next session.
5. What skincare routine should I apply in between sessions?
Depending on the size of the area you treat during your laser hair removal session, the appointment can last from ten minutes (i.e. underarms) up to an hour and a half (i.e. full body). The laser will heat up the skin around the hair a bit as well so it is possible that you experience redness and irritation. However, those should be gone within a few hours.
Immediately after your session and within the next seventy-two hours, you must avoid very hot showers, the swimming pool, the gym or any physical activities that may heat up the skin. Indeed, the heat of the laser stays under the skin for up to twenty-four hours. Avoid direct sunlight and wear SPF 50 if you expose yourself to the sun.
A few weeks after your initial treatment, you may notice less hair growth and maintenance. Indeed, the follicles shed the hairs that were in the anagen phase and that were successfully targeted. Hairs that were not in this phase will start or continue to grow.
You may exfoliate your skin a week after your session of twice a week until a few days before your next appointment. Indeed, exfoliating leaves the skin a bit sensitive. Refrain from waxing or plucking. Doing so would remove the hair along with the root leaving nothing to target during your next session. Indeed, a completely new hair needs at least six weeks to fully grow.
You may shave between laser hair removal sessions but know that shaving stimulate hair growth. Wait at least ten days after your previous session. You will have to shave again a day before your next appointment.