Most people start treating dark spots without knowing what kind of pigmentation they're dealing with. The products go on. The routine gets built. And when nothing improves, the assumption is that the products aren't strong enough.
More often, the problem is that the wrong type of pigmentation is being treated with the right approach for a different type. Melasma and post-inflammatory hyperpigmentation (PIH) look similar on the surface. They both appear as darker areas on the face. But they're driven by different mechanisms, they respond to different strategies, and treating one like the other is one of the most common reasons pigmentation stalls or gets worse.
What Each One Actually Is
Post-inflammatory hyperpigmentation (PIH) is a mark left behind by a specific event. A breakout heals and leaves a dark spot. A mosquito bite fades but the discolouration stays. A patch of eczema resolves but the skin beneath is darker than the surrounding area. In each case, there was a trigger, the skin responded with inflammation, and the inflammation caused melanocytes to deposit excess pigment in that area.
PIH is tied to a moment. Once the trigger is gone, the mark is essentially a stain that fades as the skin renews itself. It may take weeks or months depending on depth and skin tone, but the process is generally moving in one direction.
Melasma is different in almost every way that matters for treatment. It doesn't need a pimple, a scratch, or a sunburn to appear. It tends to show up as larger, more diffuse patches, often symmetrical, across the cheeks, forehead, upper lip, or bridge of the nose. Some people describe a mask-like pattern.
What drives melasma is internal. Hormonal shifts (pregnancy, contraceptive changes, perimenopause), heat exposure, visible light, and stress can all activate it. It cycles. It worsens in summer and may partially fade in winter without disappearing. It responds to triggers that are harder to remove than a breakout. And critically, the melanocytes involved in melasma aren't just overproducing pigment in response to a single event. They're in a state of ongoing hyperactivity that persists even after visible improvement.
That persistence is what makes melasma so frustrating and why the treatment approach needs to account for it.
How They Compare
| PIH | Melasma | |
|---|---|---|
| Pattern | Scattered spots, traceable to specific events | Symmetrical patches, often both cheeks, forehead, upper lip |
| Trigger | Specific: acne, injury, irritation, sun damage | Systemic: hormones, heat, visible light, stress |
| Behaviour | Relatively stable once formed, fades over time | Cycles with seasons, hormones, and heat exposure |
| Response to aggressive treatment | Usually improves | Often worsens (rebound effect) |
| Typical fading timeline | 4 to 12 weeks with consistent treatment | 3 to 6+ months, often requires ongoing management |
Why Treating Melasma Like PIH Makes Things Worse
Most over-the-counter brightening products are designed for PIH. They exfoliate, accelerate cell turnover, and work on the surface layers where post-inflammatory pigment sits. For a straightforward dark mark left behind by a breakout, that approach can be effective.
Melasma doesn't respond to that logic. Because the melanocytes driving melasma are already in a hyperactive state, aggressive topicals can push them further. Strong acids and frequent peels create inflammation. Inflammation signals melanocytes to produce more pigment. The patch you were trying to fade becomes darker.
The cycle is predictable. A strong treatment produces short-term improvement as the surface layers shed. The pigment looks lighter for two to three weeks. Then it returns darker than before because the inflammatory response from the treatment reactivated the melanocytes underneath. The instinct is to try something stronger. The stronger treatment creates more inflammation. The cycle deepens.
This isn't a failure of effort or commitment. It's the wrong framework applied to the wrong problem. Once you understand that melasma is driven by melanocyte hyperactivity rather than residual pigment from a past event, the logic shifts. The goal with melasma is to calm and manage, not to strip and accelerate. That backfire and rebound dynamic is one of the biggest reasons melasma feels impossible to treat when the approach is wrong.
How to Tell Which One You Have
If you're not certain which type you're dealing with, these patterns can help. Neither list is a diagnosis, but they narrow the field.
Signs that point toward melasma
- Symmetrical patches: both cheeks match, or there are matching areas on the forehead
- Upper lip shadow that darkens and lightens, sometimes in rhythm with your cycle
- Timing linked to hormonal changes: pregnancy, starting or stopping contraception, perimenopause
- Seasonal cycling: worse in summer, partially fades in winter without disappearing entirely
- Rebound pattern: peels or aggressive treatments produced temporary improvement followed by darker return
Signs that point toward PIH
- Individual spots you can trace to a specific breakout, injury, bite, or irritation
- Marks concentrated in areas where you typically break out (jawline, chin, cheeks)
- Gradual fading over time without cycling or seasonal fluctuation
- No connection to hormonal changes or heat exposure
- Responds predictably to consistent brightening treatment
If your pattern doesn't fit neatly into either list, it's possible to have both simultaneously. Melasma as a background condition with PIH layered on top from breakouts or irritation is common. A dermatologist can often distinguish them by examination, and a Wood's lamp can help determine how deep the pigment sits, which affects the approach.
Why This Distinction Changes Everything
Knowing which type you have doesn't just affect product choices. It changes the entire strategy.
PIH is a fading problem. The pigment is there, it needs to clear, and the question is how to support that clearing process while preventing new marks from forming. Consistent topicals, sun protection, and time are usually enough. The timeline for PIH fading depends on depth and skin tone, but progress tends to move in one direction once the right routine is in place.
Melasma is a management problem. The pigment is being actively produced by melanocytes that remain hyperactive. Clearing the surface without addressing the drivers means it returns. The strategy shifts from "fade the mark" to "reduce melanocyte reactivity and manage the triggers that keep them active." That involves gentler topical approaches, broader trigger management (including heat and visible light, not just UV), and internal support for the hormonal and inflammatory factors that sustain it.
Getting the type right isn't a minor detail. It's the difference between a routine that compounds progress over time and one that keeps resetting itself every few weeks.
Where to Go from Here
If your pattern points toward PIH, the path is relatively straightforward. The right ingredients targeting the right stage of the pigment process, structured into a consistent routine, will handle most of the work.
If your pattern points toward melasma, the approach needs to be broader and more patient. Understanding your trigger profile comes first, because you can't manage what you haven't identified. From there, a prevention framework built around relapse reduction matters more than any single product, and the treatment options look different when the goal is long-term management rather than one-time clearing.
Whichever type you're dealing with, the fact that you now know the difference puts you ahead of most people still cycling through products wondering why nothing sticks.
