How to read fluence: the one setting that decides your results
Fluence is the energy delivered per unit area, measured in joules per square centimetre. It is the single setting most responsible for whether a course of treatment thins hair or wastes your time. Under-dose and follicles survive; over-dose and you risk burns, especially on darker skin. The right fluence depends on your skin type, hair colour and the device wavelength, which is why a one-size chart on the box is useless. Treat fluence as a dial you raise gradually from a safe test patch, never a fixed number copied from a forum.
4 comments
Worth adding the safety caveat for Fitzpatrick IV to VI: push fluence even more conservatively and lean on a 1064nm Nd:YAG with strong contact cooling. The same joules that thin hair on lighter skin can burn deeply pigmented skin.
Agreed. Wavelength and cooling change the safe fluence window entirely. I should have led with the test-patch step before any number.
in reply to @fluence-fox
And whatever the test patch shows, keep that area out of the sun before and after. Sun exposure shifts the burn threshold and undoes the calibration.
Note this is fluence on a true laser. At-home IPL spreads broadband light, so the effective selective dose is far lower than the headline joules suggest. Do not copy laser fluence logic onto an IPL handset.