Page 108 - Chapter 3 - An Introduction to Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
Should we use longer pulses to reduce the pain in LHR?
We need to apply a certain amount of energy to achieve the desired result. The pulsewidth determines the power of this energy.
A short pulse will induce a higher peak temp in the epidermis – more pain. So, if we use a longer pulse, with the same energy (fluence) will it be less painful since the peak temp, and rate of increase is lower?
Figure 53 – The same applied total energy can induce either high or low peak temperatures, depending on the time taken to apply it – note all the blue shapes represent the same total energy
We are trying to ensure that the epidermal cooling rate is faster than the epidermal heating rate. If this succeeds, then the peak temperature in the basal layer and the pain will be reduced.
The cooling rate depends on the cooling efficiency - ice packs are best, with gel on the skin!
The heating rate depends on the fluence and pulsewidth (power density).
________________________________________________________________________ 108 Chapter 3 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2022