“Permanent Hair Reduction”
Another confusing definition. In 1998, the US Food and Drug Administration (FDA) began allowing some manufacturers of hair removal lasers and flash lamps used for epilation to use the term “permanent hair reduction” which the agency defines as: The long-term and stable reduction in the number of hairs regrowing after a treatment regime. The number of hairs regrowing must be stable over a time greater than the duration of the complete growth of the hair follicles, which varies from 4-12 months according to body location. Permanent hair reduction does not necessarily imply the elimination of all hairs in the treatment area. For clearance purposes, FDA requires that hair counts be measured at3, 6, 9, and 12 months following the last treatment.
The hair follicle begins at the bulb, which is found in the subcutaneous layer of the skin. The bulb is surrounded by a matrix that keeps the hair follicle alive. A thickened area of the root sheath which lies just above the bulb is called the bulge. The bulge contains stem cells that are necessary for regeneration of the hair follicle. The bulb and the bulge are considered the “cellular center” of the hair follicle. Keep in mind the goal of hair removal is to cause permanent thermal damage to the hair follicle, bulb, and bulge so it will no longer grow hairs.
Lasers and IPLs have three chromophores which are blood, this includes some veins and some sun damage (some sun damage turns red instead of brown), water, pigment or melanin hyperpigmentation. Melanin is concentrated in the hair shaft and upper part of the bulb but may also be found in the bulge. This is important because melanin is the chromophore which absorbs he laser light and generates heat which I delivered in into the bulb and bulge destroying the follicle. Blonde hair has no pigment which is why it is not treatable with laser hair removal.
