What is melanin and where does it come from?
Melanin is a natural pigment produced by specialised cells called melanocytes, located in the deepest layer of the epidermis. Every person has roughly the same number of melanocytes regardless of skin tone — the difference in skin colour comes from how much melanin those cells produce and how it is distributed, not how many pigment cells are present.
There are two main types: eumelanin (brown-black pigment, the dominant type in medium to dark skin) and pheomelanin (red-yellow pigment, more dominant in fair skin and red hair). Most people produce a mix of both, and the ratio is largely genetic.
Why melanin production increases — and causes pigmentation
Melanocytes are triggered to produce more melanin by several factors: UV radiation (the most significant driver — melanin is the skin's natural defence against sun damage), hormonal changes (oestrogen and progesterone, which is why melasma is linked to pregnancy and the contraceptive pill), inflammation (any injury, breakout, or irritation can trigger localised overproduction), and genetics (Fitzpatrick Type IV–VI skin has naturally more reactive melanocytes).
When melanocytes are overstimulated in a localised area, they deposit excess melanin faster than it can be evenly distributed — creating a visibly darker patch. This is the underlying mechanism behind sun spots, melasma, and post-inflammatory hyperpigmentation. The type of pigmentation differs, but in every case, the root cause is the same: melanocytes producing too much melanin, too fast, in one spot.
Melanin and darker skin tones
Darker skin (Fitzpatrick Type IV–VI) contains more active, more reactive melanocytes than fairer skin. This provides genuine natural benefits — greater inherent UV protection and a lower (though not zero) skin cancer risk — but it also means darker skin responds more dramatically to any trigger. The same breakout, sunburn, or aggressive skincare product that leaves faint marks on fair skin can leave pronounced, longer-lasting pigmentation on darker skin.
This is why treatment for darker skin tones must be approached differently — gentler introduction of active ingredients, careful peel selection, and consistent visible-light-filtering SPF are essential to avoid triggering the very pigmentation response the treatment is meant to correct.