Multiple treatment sessions with intense pulsed light (IPL)/laser have been shown to provide long-term reduction of hair. In general, 6 to 8 IPL/laser treatment sessions have been shown to give up to 80-90 % of no hair regrowth. After 6-8 sessions, the rest of hair that persists and grows is the left 10-20% and this hair is normally very thin and not well visible. If patient wants, he/she can do a few more treatment sessions in order to get even better results. Afterwards, patient may need one treatment session every 6 or 12 months in order to get rid of the little thin and slightly visible hair that will grow very slowly and not be a major disturbance for the person. As such, we can achieve to get permanent no hair growth results but no one can ever stop the very thin hair to grow for ever as this process of hair growth depends on the biological programming of hair growth in the living skin for a whole life-time. Fully stopping hair growth will be possible only if we will find out how to stop biological programming of hair growth in the depth/thickness of our skin.

The number of sessions depends on various parameters, including the area of the body treated, skin color, coarseness of the hair, reason for hirsutism and sex. Coarse dark hair on light skin is easiest to treat. Hair on darker skin is harder to treat. Finer hair is only sometimes affected. Certain areas (notably men's faces) may require considerably more treatments to achieve desired results. In addition, since hair grows in several phases (anagen, telogen, catagen) and laser or IPL can only affect the currently actively growing follicles in the anagen phase, several sessions are needed to eliminate hair growth in all phases of growth. 

It's also important to note that laser or IPL does not work well on light-colored hair and most fine vellus hair ("peachfuzz") as the lack of pigmentation in the hair does not allow the light energy from the laser/IPL to be absorbed by the hair and cause hair destruction.

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Vellus hair, colloquially referred to as 'peach fuzz' or 'bum fluff' is short, fine, light-colored, and barely noticeable hair that develops on most of a person's body from his/her childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital areas, the navel and scar tissue. The density of hair – the number of hair follicles per area of skin – varies from person to person. Each strand of vellus hair is usually less than 2 mm (1/13 inch) long and the follicle is not connected to a sebaceous gland.

Vellus hair is most easily observed on children and adult women, as they generally have less terminal hair to obscure it. Vellus hair is not lanugo hair. 
Lanugo hair is a much thicker type of hair that, in human forms, normally grows only on fetuses. 

Vellus hair is differentiated from the more visible terminal or androgenic hair, which develops only during and after puberty, usually to a greater extent on men than it does on women.

Production
Vellus hair replaces lanugo hair on a human fetus at 36 to 40 weeks of gestation. The growth cycle of vellus hair is different from the growth cycle of terminal hair At puberty, the androgen hormone causes much of the vellus hair to turn into terminal hair and stimulates the growth of new hair in the armpit and the pubic area. In men, this change in vellus hair occurs on the face and the body.

Function
Vellus hair is a thermal insulation for the body. This insulation regulates body temperature. The function of vellus hair on sweat is that of a wick. While a skin pore is open, sweat wets a strand of vellus hair. The sweat on the external part of the strand evaporates. More sweat wets the external part of the vellus strand and then evaporates. This process is perspiration. There are similarities in vellus hair and intermediate hair. Neither a vellus strand nor an intermediate strand has a distinct medulla. Hormones in the body cause the hair follicle to change a strand of vellus hair into a strand of intermediate hair. This process occurs at puberty.

Complications
The unusual growth of vellus hair is a side effect of some types of disease and some types of mental disorder. An abundance of vellus hair can develop from an increase in the production of the cortisol hormone in a person with Cushing's syndrome. Anorexia nervosa increases vellus hair. Vellus hair can also be found in men with male pattern baldness or hirsutism. Hormonal fluctuations in pregnant women cause foetal vellus hair to change to terminal hair. The terminal hair is usually shed after the birth of the baby upon the return of the hormones to the normal levels.