Page 38 - Chapter 3 - Laser/IPL Hair Removal
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Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
When the fluence is increased to 20 J/cm2 the pain receptors are more likely to be triggered in all skin colours for each wavelength – but the Nd:YAG is still the least likely to do so until skin colour 4 (Figure 9).
Figure 9 - Epidermal peak temperatures for four wavelengths at 20 J/cm2
At 20 J/cm2 even light-coloured skins will experience pain at the lower wavelengths – this is simply because melanin absorbs more strongly as the wavelength drops towards 400nm.With a 30 J/cm2 (Figure 10) pain is even more likely to occur in all skin colours with all wavelengths.
Figure 10 - Epidermal peak temperatures for four wavelengths at 30 J/cm2
Obviously, higher fluences induce pain more easily than lower ones. But, the wavelengths are also important, as can be seen in all three figures above. In each case, surface skin cooling must be applied to mitigate the high temperatures which occur in the basal layer.
________________________________________________________________________ 38 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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