Will Shaving Before Laser Hair Removal Result in Coarse Hair?

When undergoing laser hair removal treatments, it is important
that you NOT wax or pluck the hair 4-6 weeks before starting treatment and
in between each treatment session. The reason for this is that the laser
can only be effective if there are hairs in the follicles within your
skin. If you pull the hair out of the follicle as with waxing or
plucking, the laser cannot deliver the desired heat energy to the follicle
because it needs a hair as its target. Therefore, you can see now how the
follicles need to have a hair target in them in order for the laser to
damage the hair follicle. The goal of laser hair removal is to treat the
hair follicles so that they will not produce more hair.

You were told correctly to shave between the treatments because shaving
cuts the hair at the level of the skin and leaves the hair below the skin
in the follicle. If you are concerned with seeing a "moustache" between
sessions then you can just shave more often. As your treatments progress,
the hair will be greatly reduced in count and in texture.

Lasers used for hair removal rely on a beam of high intesity light (Light Amplification by Stimulated Emission of Radiation) focused to a specific wavelength (pigment) and target. Important to note that hair grows in cycles or phases (anagen, telogen and catagen) or "growing", dorment, or transitional. Hair in different parts of the body grow at different rates, and also go through growth phases/dormency at different rates.

Lasers are only effective if the hair is in the active growth phase--it doesnt kill the hair in dorment or transitional phases. Therefore, each laser treatment kills only those hairs in active growth phase (only a percentage of all hairs present in a particular area) and therefore requires multiple treatments over time to get an appreciable result.

Shaving is recommended between treatment because the process of shaving does not throw off the growth cycle process, as does plucking and electrolysis. As such, more hairs will be in active growth phase when you get your treatments. If you pluck or undergo electrolysis, hairs in active growth phase are disrupted in their cycles and my throw off the number of hairs that will be in active growth when it is time for your next treatment with the laser. This results in less effective treatment and more required treatments to get to the desired reduction in hair growth.