A questionnaire about sunburn, repurposed
Thomas Fitzpatrick developed the classification in the 1970s to guide ultraviolet A dosing for psoralen plus UVA therapy in psoriasis, so a phototherapy dose could be set without burning the patient.
The original questions were about sunlight rather than lasers. A patient was asked how their skin reacted to 45 to 60 minutes of early summer noon sun at northern latitudes between 20 and 45 degrees, how painful the resulting sunburn was, and how much tan appeared within a week. Types V and VI, covering darker skin, were added later.
That is worth sitting with in a clinic three degrees north of the equator, where noon sun is a daily fact and nobody is being dosed for psoriasis. The instrument reached laser medicine because nothing better arrived.
Why melanin changes the arithmetic
A laser works by putting energy into a target that absorbs it, and for most pigment work that target is the unwanted pigment. Melanin in the epidermis absorbs laser energy too, and it sits above everything else, in the way.
Clinical reference sources put it plainly: melanin in the epidermis acts as a chromophore, absorbing more laser energy and increasing the risk of adverse events from injury to the epidermis, and the risk of hyperpigmentation or hypopigmentation after a procedure is higher in Fitzpatrick types IV through VI.
That is the whole reason skin type appears anywhere near a treatment plan. More pigment at the surface means more energy intercepted before it reaches the target, and more heat where nobody wanted it. The consequence is rarely dramatic. It usually looks like a mark that darkens after the treatment meant to lighten it, the mechanism set out in why dark marks after acne linger longer in richly pigmented skin.
What changing the settings actually means
The phrase gets used loosely, so here is what sits behind it, as principle rather than protocol. When skin holds more pigment, a plan generally moves towards gentler energy delivered with more care for the surface, favouring the target over the layer above it. The skin is often prepared beforehand and cooled around the treatment, with less appetite for a fast result and more tolerance for a slow one.
What this article will not do is give you a number. Not a fluence, not a wavelength, not an interval. A setting has no meaning detached from the diagnosis, the device, the area and the person in the chair, and a figure carried in from an article is more often used to argue with a doctor than to understand one. The useful version of this knowledge is directional: it tells you what a careful plan looks like from the outside, and lets you notice when one does not.
It also explains something patients find counterintuitive. A treatment that is working properly in more pigmented skin often feels underwhelming on the day. Restraint is the technique.
The scale is weakest exactly where this clinic works
A 2026 editorial in Cutis, on the limitations of Fitzpatrick skin type as a proxy for skin colour and race, is blunt about the problem. The scale is often used beyond its intended purpose, does not adequately capture variability in baseline pigmentation, undertone or inflammatory response, and those limitations are especially pronounced in phototypes IV to VI, which the editorial describes as encompassing highly heterogeneous populations. It adds that treatment decisions, including laser settings and assessment of pigmentary risk, are often guided by Fitzpatrick type despite the variability within each group, that the scale correlates poorly with measured constitutive skin colour, and that recognising erythema is harder in darker skin where the familiar visual cues are less apparent.
Types IV to VI describe most of the people who walk through this door. The tool is at its least reliable in precisely the range where it is asked to do the most work.
An older problem sits underneath it. The classification was always partly subjective, resting on what a person remembers about burning and tanning, and reference sources note that people with skin of colour report fewer painful burns or tanning episodes. A number derived from a memory of sunburn is a thin thing to hang an energy setting on.
One trial, in the skin this country actually has
A randomised, assessor-blinded melasma trial gives a useful picture. Its participants were Fitzpatrick types III to IV, type IV predominating, closer to the population here than most published laser research manages.
Two of the three arms were picosecond lasers. They differed in wavelength, in pulse duration and in their result at the end of the study, which is a reminder that a category name on a treatment list can cover two different machines. Post-inflammatory hyperpigmentation occurred in one patient in each of the three arms, roughly 5 per cent, and settled on its own within one to six months.
Read that carefully rather than comfortably. It happened inside a controlled trial, with selected patients and a published protocol, so it is not a rate to expect from any treatment anywhere, and it does not mean pigment always settles by itself. It means a treatment aimed at pigment can produce pigment in this range of skin, and a plan has to account for that. The reasons pigment returns even when nothing went wrong are set out in why pigmentation comes back.
What a doctor does with a scale that is not good enough
The Cutis editorial ends where an honest article has to end. Fitzpatrick skin type should be used for what it was designed for, estimating ultraviolet response, with additional descriptors and a more detailed assessment of pigmentation alongside it. Objective alternatives exist, spectrophotometry and melanin index assessment among them, limited by the equipment required and their feasibility in routine practice, and none has achieved widespread adoption.
There is no replacement to announce, and any clinic claiming its own method beats the scale should be asked for the evidence. What happens instead is that the type becomes one input among several. How the skin behaved after previous treatments. How it responded to a scratch or an old insect bite. What the pigment actually is, since the picosecond laser used here is only ever the answer to a diagnosis already made.
None of which is settled from a photograph or a message. What a first consultation decides is mostly this: what the problem is, and how much room there is to work in.
A scale invented to dose sunlight has ended up carrying more weight than it was built for. Knowing that is a reason to treat the number as the beginning of the conversation rather than the end of it.
