Brown spots, melasma, post-inflammatory hyperpigmentation: Identify them correctly before treating them

Not all brown spots tell the same story. Some result from years of cumulative sun exposure; others appear within a few weeks following a hormonal surge; still others leave a mark where a long-gone pimple once was. Three different mechanisms, three spots that look alike to the naked eye—and yet they are not treated in the same way.

Three spots, three distinct origins

The MSD Manual defines hyperpigmentation as a localized darkening of the skin associated with excessive melanin production, triggered by several possible mechanisms. Solar lentigo is a well-defined brown spot that appears on areas most exposed to the sun after years of cumulative exposure. Melasma, on the other hand, is a more diffuse and often symmetrical form of hyperpigmentation that affects the forehead, cheeks, or upper lip and results from a combination of hormonal and sun-related factors. Finally, post-inflammatory hyperpigmentation appears after a skin lesion—such as an acne breakout or irritation—exactly where the skin was damaged.

How Melanin Is Actually Formed

These three types of spots share the same underlying cellular mechanism: overactivation of tyrosinase, the key enzyme that triggers melanin synthesis in melanocytes. When exposed to a stimulus—such as UV rays, inflammation, or hormones—these cells produce more melanin and transport it to the skin’s surface, where it forms the visible spot. It is this common mechanism that explains why certain active ingredients, without directly affecting melanin production itself, can influence spots that have different underlying causes.

Three spots, three stories—but one thing in common: the sun, which always triggers the same reaction.

The sun and hormones: two common driving forces

These three types of dark spots often share a common trigger: UV exposure, which directly stimulates melanin production. Melasma also has a significant hormonal component, frequently associated with pregnancy or hormonal birth control. Post-inflammatory hyperpigmentation depends mainly on the severity of the initial lesion: the more severe it is, the more likely the residual mark is to be visible and take a long time to fade, particularly on darker skin tones.

Why Sun Protection Remains the Most Important Step

A study published on EM Consulte showed that sunscreen that also protects against visible light—and not just UV rays—significantly reduced melasma flare-ups compared to UV protection alone. For other types of skin spots, the recommendation remains the same at a minimum: daily sun protection, even on cloudy days, remains the most important factor in preventing existing spots from darkening and new ones from appearing.

This helps even out your complexion without rushing

Beyond sun protection, consistency is more important than intensity. Certain active ingredients known for their effect on skin tone evenness work gradually, over several weeks, by slowing the transfer of melanin to the skin’s surface. Conversely, using multiple exfoliating or brightening ingredients in the hope of speeding up results often weakens the skin barrier—which can perpetuate the inflammation that is the very cause of certain post-inflammatory dark spots.

Niacinamide & Biotech Serum — VIBRE PARIS

It is this philosophy of consistency—rather than immediate results—that guided the formulation of the niacinamide serum—one step among many, never a substitute for daily sun protection, a concept we’ve already explored in our article on cosmetic overload.

Identifying the exact nature of a spot before taking action can prevent a lot of disappointment: a solar lentigo, melasma, and a post-inflammatory mark do not require the same amount of time or exactly the same approach to fade.

Sources

• MSD Manual (Professional Edition) — Clinical Classification of Pigmentation Disorders and Associated Mechanisms
• Merck Manuals (Consumer Edition) — Definition, Triggers, and Management of Melasma
• EM Consulte (medical publishing platform) — study on the effectiveness of extended photoprotection in melasma