How laser hair
removal works
Why it takes six sessions, and what is really happening under the skin
Almost every question we get about laser hair removal comes down to one thing nobody explains properly: hair grows in cycles. Once that makes sense, the rest does too.
This article is written in two parts. Part one is the plain-English version. Part two goes into the detail, for anyone who wants it.
Start here
What the laser is doing
A pulse of light passes through the surface of your skin and is absorbed by the pigment inside the hair follicle. That pigment turns the light into heat, and the heat disables the part of the follicle that grows new hair. The skin around it is cooled and left alone.
Why one session is never enough
At any given moment only a portion of your hair is actively growing. The rest is resting or shedding, and a follicle that is resting has little pigment in it for the laser to find. So each session treats the follicles that happen to be awake that day. Come back four to six weeks later and a different set is awake. That is the entire reason for the schedule.
What you will see, week by week
For about two weeks after each session the treated hairs sit in the follicle and then push out. It looks exactly like regrowth, and it is not: it is shedding. After that the area stays smooth for several weeks. By your third session most people have stopped shaving daily. By the sixth, what comes back is fine, sparse and pale.
What 'finished' looks like
A long-term reduction of around ninety percent is a realistic target for dark hair. Not zero hair forever. Anyone promising you that is overselling. What you get is skin you stop thinking about, with a maintenance session once or twice a year on hormonally driven areas.
The technical detail
Selective photothermolysis
The principle behind every hair-removal laser, described by Anderson and Parrish in 1983. Choose a wavelength absorbed more by your target than by the surrounding tissue, deliver it in a pulse shorter than the time the target takes to cool, and you heat the target while leaving its surroundings largely undisturbed. Everything else is engineering around that idea.
The hair cycle, properly
Anagen is the active growing phase, when the follicle is rich in pigment and attached to the stem cells that matter. This is the only phase where treatment is meaningfully effective. Catagen is a short transitional phase. Telogen is resting, when the hair is no longer connected to its blood supply. The proportion in anagen at any moment varies by body site: roughly 85 percent on the scalp, but only 20 to 30 percent on the legs and around 65 percent on the chin. That is why the face needs more sessions than the legs, and why the intervals differ by area.
Why the interval matters more than the number
Coming in every two weeks does not speed anything up. It treats the same dormant follicles twice and achieves nothing except cost. The interval is set to the length of the resting phase at that body site, which is why we space facial work at four weeks and legs at six.
Hormones and new follicles
Hair on the face, chin, neck and abdomen in women is frequently hormonally driven, by PCOS, thyroid changes, pregnancy or menopause. Treatment reduces the follicles that exist, but hormones keep recruiting new ones from follicles that were previously dormant. This is not treatment failure; it is the underlying cause continuing. These areas usually need a maintenance session once or twice a year. Legs, underarms and back rarely do.
Why shaving, and never waxing
Shave the area the day before: the laser needs the follicle intact and full of pigment, but a long hair above the skin only absorbs energy at the surface, where it causes discomfort and nothing useful. Waxing, threading and plucking pull the follicle out entirely, leaving the laser nothing to find. Four weeks with no waxing before your first session, and only shaving between sessions after that.
Good to know
How many sessions will I need?
Six to eight for most areas, four to six weeks apart. Facial and hormonally driven areas usually need maintenance afterwards.
Why is hair still there after my first session?
It is shedding, not regrowing. Treated hairs take one to two weeks to push out of the follicle. Do not pluck them; let them come away on their own.
Does it work on blonde, grey or red hair?
Not well. Light-based hair reduction needs pigment in the hair to work on. We will tell you straight at your consultation rather than sell you a course that will disappoint you.
Can I shave between sessions?
Yes, and you should. Shaving leaves the follicle intact. Waxing and plucking do not.
Thirty minutes, no pressure
We look at your skin properly
Your history, your concerns, what you have already tried and what your routine looks like now.
We tell you the truth
What will help, what will not, and what you may not need at all. If something else suits you better, we will say so.
You leave with a plan
Written, with clear pricing and no pressure. Whether you book is entirely up to you.
More from the journal
Laser hair removal on deeper skin tones
What actually matters, and why nobody gets turned away here
Before and after your first session
Everything to do in the two weeks either side, in one place
Six things people believe about laser that are not true
Including the one that costs people the most money