Laser/IPL Hair Removal – How many follicles do we kill each treatment?

All hair follicles grow according to a cycle – ‘anagen, catagen, telogen’. The follicle germative cells promote anagen hair growth at consistently regular intervals resulting in periods of active growth, followed by inactivity. The duration of these periods depends on the which part of the body is being considered. I created a computer model to… Continue reading Laser/IPL Hair Removal – How many follicles do we kill each treatment?

What is the ‘best’ interval between hair removal sessions (after treatment by lasers or IPLs)? Part 2.

I wrote a blog post back in September 2021 discussing my thoughts on the how to determine the optimum interval between laser/IPL hair sessions. It proved very popular amongst my readers. But, as soon as I posted it I began to doubt my own conclusions. Back then I suggested that we should wait for an… Continue reading What is the ‘best’ interval between hair removal sessions (after treatment by lasers or IPLs)? Part 2.

How strongly are different laser wavelengths absorbed in melanin and blood?

These days we use a wide variety of lasers and IPLs to treat various targets in the skin. Two major targets are hair and blood vessels. But how much of the laser/IPL light is actually absorbed by these targets? Using data from two very clever scientists (Steve Jacques and Scott Prahl) it is relatively easy… Continue reading How strongly are different laser wavelengths absorbed in melanin and blood?

Thick and thin hair – how much light energy do they actually absorb during photothermal treatments?

How thick is a hair? Well, according to some research by physicist, Brian Ley (they do all the best research!!!), it ranges between 17 and 181 microns in diameter (see his results here). That is between 0.017 and 0.18 mm. So, that means that their cross-sectional areas [A = pi x (radius)2] are between 0.0000023 and 0.00026 square… Continue reading Thick and thin hair – how much light energy do they actually absorb during photothermal treatments?

Laser Tattoo Removal – wavelengths and anisotropy

I’ve just made a couple of little animations looking at the differences between the laser wavelengths we use for tattoo removal and how anisotropy comes into play. You might be surprised at what actually happens in the skin. Anisotropy is rarely discussed in the laser tattoo world, yet it has significant effects on treatment outcomes.… Continue reading Laser Tattoo Removal – wavelengths and anisotropy

Light penetration into skin and the subsequent temperature rise

Where does light go when it enters the skin? Well, it’s actually quite complicated! Some of it reflects off the skin surface, some is absorbed in the melanin (basal layer), some penetrates through to the fatty tissue, while some is turned around and escapes back into the air. The follow slideshow gives a simple explanation… Continue reading Light penetration into skin and the subsequent temperature rise