I am asked this question all the time!! It’s tricky to answer because it’s not at all obvious. The short answer is: the interval should track telogen duration, not anagen duration. Anagen tells you what you can kill today; telogen tells you how fast the next treatable cohort arrives. See what I mean?!?! The Merhag… Continue reading What is the ‘best’ time interval between laser/IPL hair removal sessions?
Month: July 2026
The physics of sunscreen, SPFs and the energy flow…
For many years we have been told a simple public health message: “Wear sunscreen, especially during the summer.” It is well-intentioned advice, but as a physicist I have always found it rather unsatisfying. Nature is rarely that simple, or linear (In fact, in this universe, ‘linear’ is the exception rather than the rule!). If we… Continue reading The physics of sunscreen, SPFs and the energy flow…
If a Nd:YAG laser can only produces 1064 nm light… where do all the other wavelengths come from?
It’s an excellent question. Most laser users know that a KTP crystal converts 1064 nm into 532 nm by “frequency doubling”. But what about the other wavelengths—585 nm, 650 nm and the various colours advertised by some manufacturers? Is the laser somehow producing entirely new wavelengths? Well… yes. But not quite in the way many… Continue reading If a Nd:YAG laser can only produces 1064 nm light… where do all the other wavelengths come from?
Paradoxical Hypertrichosis and Synchronised Growth – revisited
Two things get muddled constantly in laser and IPL hair removal, and the confusion has inflated one of the most over-reported “side effects” in the field. The line is actually simple: Synchronised growth happens where you treated. Paradoxical hypertrichosis (PH) happens where you didn’t. That single distinction settles most of the argument. The trouble is… Continue reading Paradoxical Hypertrichosis and Synchronised Growth – revisited
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