For our lightsheer diode laser, we suggest eight or more treatments to provide long term hair reduction for most patients. Some need less and others need more.
You should not think of "a number of sessions needed" to reduce hair growth. More sessions are needed in the beginning (around 3-4 for the body and 5 for the face). After that, the sessions should be spaced out significantly in order to touch up areas from time to time. It does depend on the person and type of skin so a darker skinned patient may need more sessions. Also, if a patient has excessive hair growth due to a hormonal imbalance, more sessions may be needed. Consult your doctor so he or she can examine the areas that you would like treated for your best options.