Melanin and Pigmentation: What Gives Skin Its Color (and Why Marks Linger)

Melanin decides your skin tone, how you react to the sun, and why a pimple can leave a dark mark that lasts for months. It is also one of the most misunderstood things in skincare. Here is what it actually is, what controls it, and what that means for your routine.

What Melanin Is and Where It Is Made

Melanin is the pigment in your skin. It is made by cells called melanocytes, which sit in the deepest layer of the epidermis. They produce it inside small packets called melanosomes, which are then passed along to the surrounding skin cells^[1]. The key enzyme in the process is tyrosinase, and it helps build two kinds of melanin: darker eumelanin and lighter pheomelanin^[1].

What Sets Your Skin Tone

There is no single "skin tone gene". More than 150 genes affect skin color, directly or indirectly^[1]. In a study that compared skin color measurements with skin biopsies across different ethnic groups, the total amount of melanin in the epidermis was the main determinant of how light or dark skin looked, and the size of the melanosomes also played a smaller role^[2]. Variants of one gene in particular, MC1R, are linked to fair skin, greater sensitivity to UV and higher skin cancer risk^[3].

A note on the sources: the skin color study was carried out by researchers at Unilever Research. It was published in a peer-reviewed journal, but you should know who ran it.

Built-In Sun Protection, With Limits

Melanin absorbs UV, and more of it means more natural protection. In one classic comparison of skin samples, about five times as much UV reached the upper dermis of Caucasian skin as reached that of Black skin. The protection comes from more than the amount of melanin: how the melanosomes are packaged and spread through the epidermis matters too^[4]. That fits with the lower rates of skin cancer seen in people with darker skin, although researchers note that the exact role of melanin in photoprotection is still debated^[5].

Natural protection is not complete protection, and it does not stop pigmentation problems. UV exposure turns up most of the signals that increase melanin production^[1], which is why sun exposure darkens skin and why sun protection stays on the list of first-line care for dark marks even in skin that is rich in melanin^[6].

The Trade-Off: Vitamin D

The same filtering that protects skin also reduces how much vitamin D it makes. In a small 1982 study, one standard dose of UV raised vitamin D levels up to 60-fold in lightly pigmented volunteers but made no significant difference in heavily pigmented ones^[7]. It was only five people, so treat it as an illustration, not a rule. If you are concerned about your vitamin D, ask your doctor about a blood test rather than skipping sunscreen.

Why Marks Linger

Melanocytes also react to inflammation. After a pimple, bite, or irritation, they can produce extra melanin in that spot, leaving a flat dark mark called post-inflammatory hyperpigmentation. It tends to affect darker skin more often and more severely, and dark marks are among the most common reasons people with darker skin see a dermatologist^[6]. We cover the difference between sun spots, acne marks and melasma in Hyperpigmentation: Sun Spots vs Acne Marks vs Melasma.

What This Means for Your Routine

• Wear sunscreen every day. It matters at every skin tone, and it is the first thing recommended for dark marks.
• Do not pick or scrub. Inflammation is what switches melanin production on after a pimple, so the calmer you keep the area, the less pigment it makes.
• Treat marks early and gently. Start one pigment-targeting product at a time, and stop if your skin stings or turns red, since irritation can darken marks.
• Be patient. Pigment fades over months, not days.
• Get changing spots checked. A mark that grows, changes shape or color, or bleeds is a reason to see a dermatologist.