Melasma, Sun Spots, and Post-Inflammatory Dark Spots: What Is the Difference?

"Dark spots" is a description, not a diagnosis. Three different things get called that, and they behave differently.

Melasma shows up as fairly even patches, usually on the face, and it comes back. Post-inflammatory hyperpigmentation (PIH) is what's left behind after something inflamed or injured the skin. Sun spots track years of light exposure.

An article can't tell you which one you have. Only an exam can.

What "dark spots" covers

Any patch of skin holding extra melanin. Doctors call it hyperpigmentation, and the umbrella is wide.

A global expert group published a consensus in December 2025 that shows just how wide. Ten dermatologists reviewed 152 papers and issued recommendations across seven different groups of pigment disorders, from melasma and PIH to freckles, darkening around the eyes, and darkening in the body folds. Every recommendation needed at least 75% agreement to make the cut.

These conditions are common. A global survey cited in that consensus found that half the people asked reported having one of the six most common pigment problems. Only 38% recognized sun exposure as harmful and protected themselves year-round.

Same brown patch, different causes, different timelines, different plans.

What melasma usually looks like

Fairly even patches on the face, and a strong tendency to return.

Dermatologists grade it with the modified Melasma Area and Severity Index (mMASI). It captures how large and how dark the patches are, and lower is better. The consensus puts a score of 4 or below in the mild category and anything above 4 in the moderate to severe range. It also sets a target for first-line treatment: at least a 30% drop in that score within 8 to 12 weeks.

Light drives melasma, so the consensus recommends sun protection factor (SPF) 50 or higher with ultraviolet A (UVA) protection. For regular outdoor exposure, it advises about a quarter teaspoon for the whole face and reapplication at least twice a day.

One disclosure on that paper. The publication lists Beiersdorf grant 001/2025. Beiersdorf, a skincare company, also provided editorial help and reported no role in the design or the data, and several authors report fees from Beiersdorf and other companies.

What is post-inflammatory hyperpigmentation?

PIH is the darkening skin leaves behind after inflammation or injury heals.

A 2024 review looked at PIH in skin of color. Its abstract and Results section use inconsistent study, participant, and face-involvement counts, so I am not treating those totals as settled. Among cases with a known trigger, 89% followed an inflammatory skin condition, and acne accounted for 97% of those.

The most useful piece of that review tracked people who got no treatment at all. Out of 346 untreated people, not one cleared completely. Sixty-two percent had partial pigment reduction, 4% had partial size reduction, and 33% did not respond. In a smaller group of 55, the average time to resolution was 68 days.

So untreated PIH often fades on its own, at least partly. Complete clearing without treatment didn't happen in this pool.

Sun spots

Solar lentigines, usually called age spots or sun spots, are darkened spots that track long-term light exposure.

The American Academy of Dermatology's patient page discusses creams and lotions plus clinician procedures, and recommends a dermatologist exam before treating an age spot. The procedures include laser therapy, controlled freezing, microdermabrasion (a machine that buffs off the surface layer), and chemical peels. In one study it cites, about 40% of patients saw their age spots disappear completely with microdermabrasion alone. Half saw them disappear when it was paired with a chemical peel. In another study on that page, 47% of peel patients had their spots fade by half.

One limit on that page: it covers age spots only. It doesn't discuss melasma, and it doesn't mention cysteamine.

When does a spot need an exam?

Any spot that's new, changing, bleeding, painful, or just bothering you.

The American Academy of Dermatology (AAD) puts it bluntly: what looks like an age spot can turn out to be skin cancer. They recommend a skin exam by a board-certified dermatologist before treating age spots at all.

Telling melasma from PIH, either one from a sun spot, and any of them from something serious takes an in-person look. So does grading severity with a scored tool. If you're unsure what a spot is, that uncertainty is your reason to book the appointment.

What Illuminate Rx is

Illuminate Rx 10% Cysteamine Pigment Corrector Complex is a cosmetic cream. Its carton reads 10% Cysteamine, Pigment Corrector Complex, and Advanced Skin Lightening, and the ingredient panel also lists glycolic acid, retinol, and two forms of vitamin C.

The directions: apply once daily to dry skin for 30 minutes, wash off, moisturize, and use broad-spectrum SPF 30 or higher during the day. Not for use during pregnancy or breastfeeding.

A cosmetic product doesn't diagnose anything, and it isn't a substitute for the exam described earlier. My search found no PubMed-indexed paper or ClinicalTrials.gov record through August 16, 2026 that names or tests Illuminate Rx. One note on the PIH review above, since people quote it loosely: its only cysteamine evidence was a single case report, and one case can't support a claim about how well anything works.

Next step

Read the linked documents below, and take any diagnosis question to a board-certified dermatologist in person. If a spot is new, changing, bleeding, or painful, book that exam before you try any product on it.