It is important to note that these studies utilized a variety of IPL devices on various skin areas, and used patients with varying hair and skin types. Thus the results are not directly comparable. In evaluating these results it is also important to remember that even a reduction of 75% indicates that 25% of the hair regrew after treatment. Permanent hair removal in these studies, as defined by the FDA, means the "long-term, stable reduction in the number of hairs regrowing after a treatment regime". The number of hairs regrowing must be stable over time greater than the duration of the complete growth cycle of hair follicles, which varies from four to twelve months by body location.
[11] No treatment to date has shown the ability to permanently eliminate all hair growth, however many patients experience satisfaction with a significant and permanent reduction.