What the Fitzpatrick scale is
The Fitzpatrick scale describes how skin responds to UV in six grades — from phototype I (very fair, always burns, never tans) to phototype VI (very dark, never burns). Originally used to set doses in phototherapy, today it is a reference point for light-based treatments.
Phototype is assessed from the history (reaction to sun) and a visual look at unexposed skin, for example on the inner arm.
Why phototype matters with light
Lasers and IPL work by selective photothermolysis — energy is absorbed by melanin. The more melanin in the epidermis, the higher the risk that energy meant for the follicle or vessel is absorbed in the skin surface and causes a burn or pigment change.
For darker phototypes, longer wavelengths, longer pulse durations and strong cooling are usually chosen, and energy is set more cautiously and verified with a test.
Phototype, hair colour and contrast
In laser hair removal, the contrast between light skin and dark hair matters, as does the melanin content of the hair itself. Grey, light-blond and red hair contain little eumelanin, so they respond poorly regardless of skin phototype.
So phototype is assessed together with hair colour and thickness, the body area and previous hair-removal methods.
Limits of the scale
The Fitzpatrick scale is subjective and does not account for ethnic background or a tendency to post-inflammatory hyperpigmentation. Two people with 'phototype III' can react differently. It also says nothing about the current state of the skin — a fresh tan temporarily raises risk regardless of the baseline phototype.
Using phototype in qualification
In practice, phototype is one input into the parameter decision, alongside hair colour and thickness, tanning history, photosensitising drugs, tendency to pigment and the reaction to a test patch. It does not replace the test or observation during a series.
Summary
The Fitzpatrick phototype is a useful but incomplete indicator. Safe work with light combines phototype with hair assessment, history, a test patch and observation of the reaction. This is part of the laser hair removal and IPL/BBL courses at OG Academy.