We answer this question several times a week. Many people think that after one laser hair removal treatment that all the hair will be gone forever. Unfortunately this isn’t the case.
First a bit of hair biology 101 – every hair on your body goes through three phases.
- First is the growth stage. In this stage the hair is actively growing and getting longer. In this phase there is rich blood supply in the hair follicle to feed the hair growth. It is the length of this phase which determines the length of the hair. On your scalp this phase can be prolonged which is the reason you can grow long hair, whereas on your arms this phase can be much shorter, so the hair grows less than an inch, then stops.
- The second phase is where the hair stops growing. the blood supply pulls back from the follicle, but the hair follicle holds onto the hair for some time.
- Finally the follicle lets go of the hair and it falls out. The follicle will remain in this dormant stage for some time, then the blood supply will return and will start growing a new hair.
The process above repeats over and over for a single hair follicle.
Now lets look at how the laser works. The laser light penetrates the skin and encounters the dark hair in the follicle and heats it up. If it is in the growth phase the blood supply is in close proximity to the hair in the follicle and the blood is heated and cauterized. This then disables the hair follicle so it can’t grow another hair. But if the follicle is in the 2nd or 3rd phases above, then the hair heats up, but the blood supply isn’t there so nothing happens.
At any one time you may have about 20% of your hair follicles in the growth phase. So if you did laser once, you might reduce the amount of hair by 20%. Do it twice and you might thin it by 40%, etc. So in theory five treatments should eliminate all the hair. But in reality the timing of your hair growth cycle is variable and unknown, so one follicle might sneak its growth phase in between two treatments. So then typically seven treatments will be required.