The theoretical explanations behind laserassisted hair removal seem logical. However, questions do remain. It is very difficult to predict the ideal patient and ideal treatment parameters for each patient. Even the same patient may respond differently to the same parameters on two different treatment sessions.
It is impossible to estimate the exact amount of energy absorbed by each hair follicle after laser irradiation owing to skin nonhomogene-ity, multilayering, and anisotrophic physical properties of hair growing at different angles in relation to the laser impact. In addition, because growing hair depths vary between 2 and 7 mm depending on the body location, laser absorption characteristics will vary depending on the anatomic site. Finally, the percentage of anagen and telogen hairs varies from site to site, from person to person, and from season to season. It is not even clear whether the treatment of anagen as compared to catagen or telogen hairs even matters.
Many studies now show the hair follicle to be an incredibly resilient structure, regrowing after a seemingly lethal injury. It is the delivery of adequate fluences, optimizing wavelengths, and pulse durations, while reducing unwanted epidermal injuries that leads to the optimal treatments of pigmented hair. Unfortunately, the treatment of unwanted light or white hairs remains a challenge.
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