Melasma vs. Post-Inflammatory Hyperpigmentation: How to Tell Them Apart and Treat Each
Melasma and PIH look similar but have different causes and need different treatments. Here's how to tell them apart and what actually works.
Both melasma and post-inflammatory hyperpigmentation (PIH) show up as dark patches on the skin, but they come from different mechanisms and respond to different treatments. Getting the distinction right can save months of trying the wrong approach.
What Is Melasma and Why Does It Keep Coming Back?
Melasma is a chronic pigmentation disorder driven by a combination of UV exposure, hormonal shifts, and genetic predisposition 1. The patches are typically symmetrical, appearing on both cheeks, the forehead, the upper lip, and the chin. They tend to be larger, with irregular but well-defined borders, and often worsen in summer or during hormonal events like pregnancy or starting oral contraceptives.
What makes melasma difficult is that it is hard to clear for good. Its pathogenesis is multifactorial: melanocytes activate inappropriately, melanin accumulates in both the epidermis and dermis, vascularization increases, and the basement membrane is altered 1. Even after treatment, pigment can return with the next sun exposure, which is why SPF is less a suggestion and more the foundation of any melasma management plan.
Up to 90% of people who develop melasma are women. Among pregnant women specifically, prevalence ranges from 15% to 50% 1.
What Is Post-Inflammatory Hyperpigmentation?
PIH is the dark mark left behind after skin inflammation resolves. A breakout heals, eczema clears, or a minor wound closes, and the melanocytes at that site overproduce pigment during the repair process 3. The result is a flat, discoloured patch that sits exactly where the trigger was: the same spot, the same shape, roughly the same size.
Unlike melasma, PIH is not hormonally driven and it does not appear symmetrically across the face. It is one consequence of one event. The good news is that PIH fades on its own over time in most cases, though that timeline can stretch to months or even years depending on depth and skin tone 2.
PIH disproportionately affects people with deeper Fitzpatrick skin types (III to VI). Research shows that 65% of African American, 53% of Hispanic, and 47% of Asian acne patients develop PIH after breakouts 2.
Melasma vs. PIH: How to Tell Them Apart
The comparison below captures the key diagnostic differences. If you are still unsure after using this, that is a reason to get a dermatologist's assessment.
| Feature | Melasma | Post-Inflammatory Hyperpigmentation |
|---|---|---|
| Cause | UV exposure, hormones, genetics | Skin inflammation or injury |
| Location | Cheeks, forehead, upper lip (bilateral) | Wherever the trigger occurred |
| Pattern | Symmetrical across the face | Asymmetrical, matches the injury site |
| Borders | Irregular but defined | Follows the shape of the original lesion |
| Triggers | Sun, hormones, heat | Acne, eczema, cuts, procedures |
| Self-resolves | Rarely without ongoing SPF | Often yes, but slowly |
| Depth | Epidermal, dermal, or mixed | Usually epidermal; dermal in deeper injuries |
Why the Distinction Changes How You Treat It
Treating melasma without consistent, broad-spectrum SPF is close to futile: UV exposure is the primary ongoing trigger, and any depigmenting work is partially undone by each unprotected exposure. The same is broadly true for PIH, where sun exposure can deepen and extend the marks, but PIH does not require the same relentless hormonal management.
For melasma, a typical protocol layers three types of action: blocking ongoing UV, interrupting melanin synthesis (with ingredients like niacinamide, azelaic acid, or kojic acid), and accelerating cell turnover. Hydroquinone at 4% concentration has long been the standard topical, though formulation and duration matter and it should not be used indefinitely without guidance 4.
For PIH, the same depigmenting actives apply, but the treatment can be simpler because the trigger is no longer active. Topical retinoids have good evidence for acne-induced PIH specifically, with partial improvement seen in up to 85% of participants in systematic review data 2. All actives in both categories require daily SPF and a patch test before wider use.
When to See a Dermatologist
Persistent pigmentation, any mark that does not improve over three to six months, or anything resembling melasma should be assessed by a dermatologist. This is particularly important for deeper, dermal melasma, which does not respond well to standard topical-only approaches and may need combination procedures. A professional can also rule out other causes of facial pigmentation, including drug reactions and post-laser PIH.
Ingredients That May Help Both Conditions
Several topical ingredients have evidence for reducing excess pigmentation in both melasma and PIH 3 4:
- Niacinamide: Reduces melanosome transfer to keratinocytes, well-tolerated, low irritation risk.
- Azelaic acid: Works on tyrosinase (the enzyme behind melanin production) and has anti-inflammatory properties. Useful for PIH where active acne is also present.
- Kojic acid: Tyrosinase inhibitor; may help reduce the appearance of surface-level pigmentation.
- Vitamin C (ascorbic acid): Antioxidant that may interrupt melanin oxidation. Light-sensitive, so formulation matters.
- Topical retinoids: Accelerate cell turnover, helping fade pigment faster. Start low, go slow, and use SPF every morning.
None of these are fast. Expect four to eight weeks before seeing measurable change.
Use This in Your Routine
Not sure whether you are dealing with melasma, PIH, or something else? The Skin Bliss Face Scanner can detect pigmentation patterns across different areas of the face, flag potential concern types, and help build a personalised routine targeted at your specific skin profile. Use it before committing to a treatment approach: scan.skinbliss.app.
FAQ
Can you have melasma and PIH at the same time?
Yes. Both can coexist, particularly in people with acne-prone skin who also have hormonal or UV triggers. A breakout can cause PIH in a spot that overlaps with a melasma patch. The treatment priorities stay the same: daily SPF, then layered depigmenting actives.
Does melasma ever go away on its own?
In some cases, melasma linked to pregnancy or oral contraceptives may fade after the hormonal trigger is removed. But UV-driven melasma rarely resolves without active management. Without consistent SPF and targeted actives, most people see gradual worsening over time.
Is PIH permanent?
Epidermal PIH is not permanent. It can fade without treatment, but the timeline depends on skin tone and how the skin was injured. Dermal PIH (where pigment sits deeper) takes significantly longer and may need professional treatment. Consistent SPF slows additional darkening while the skin heals.
Why does PIH affect darker skin tones more severely?
In skin with more baseline melanin, the melanocytes are already producing pigment at a higher rate. Any inflammatory signal can trigger overproduction more easily, leading to more intense and longer-lasting marks. This is not a problem to prevent at the level of skin type; it is a reason to treat inflammation quickly and protect with SPF every day 2.
Can I use hydroquinone for both melasma and PIH?
Hydroquinone at 4% concentration is used for both, but it should be used under professional guidance, for defined treatment periods (typically not continuously beyond three months without assessment), and always with SPF. Extended unsupervised use carries a small risk of a rebound effect called ochronosis 4.
Sources
- Artzi O, et al. "The pathogenesis of melasma and implications for treatment."
- Mar K, et al. "Treatment of Post-Inflammatory Hyperpigmentation in Skin of Colour: A Systematic Review."
- Anvery N, et al. "Management of post-inflammatory hyperpigmentation in skin of color: A short review."
- Thawabteh AM, et al. "Skin Pigmentation Types, Causes and Treatment: A Review."
