Hyperpigmentation Explained: Why Dark Spots Form and How to Fade Them

Dark spots. Sun damage. Melasma. Post-inflammatory hyperpigmentation. These terms are often used interchangeably, but they have different causes, different behaviours, and respond differently to treatment. Getting clear on which type you're dealing with is essential before you invest in anything.

The biology of pigmentation

All hyperpigmentation starts with melanocytes, the cells in your basal layer that produce melanin, the pigment that gives skin its colour. Melanocytes produce melanin in response to triggers: UV radiation, inflammation, or hormonal changes.

The melanin is then transferred to surrounding keratinocytes (skin cells) and distributed upward through the epidermis. When this process is disrupted or overactivated, you get an uneven distribution: patches, spots, or diffuse discolouration.

Know your type

Post-inflammatory hyperpigmentation (PIH) is the dark mark left behind after skin trauma: a healed pimple, an insect bite, a graze. It's caused by melanin overproduction triggered by inflammation and typically sits in the epidermis. It's the most common type in darker skin tones, and the most responsive to topical treatment.

Sun damage (solar lentigines) are the flat brown spots that accumulate over years of UV exposure, particularly on the face, hands, and chest. They represent areas of melanocyte hyperactivation. These are largely preventable (SPF) and treatable.

Melasma is a more complex, hormonally-driven form of hyperpigmentation presenting as symmetrical patches, typically on the cheeks, upper lip, and forehead. It's significantly more common in women and is strongly triggered by UV exposure, pregnancy, and oral contraceptives. Melasma is the most difficult type to treat because it has both an epidermal and dermal component; deep pigmentation doesn't respond as readily to topical agents. It also recurs without consistent sun protection.

Ingredients with clinical evidence

Hydroquinone (2–4%) is the most studied depigmenting agent available. It inhibits tyrosinase, the enzyme responsible for melanin synthesis. Effective at fading all types of hyperpigmentation, but long-term use requires caution and medical supervision at 4%+. Available OTC at 2% in many countries.

Azelaic acid (10–20%) is a dicarboxylic acid that selectively targets overactive melanocytes without affecting normal skin cells. Prescription-strength (20%) has strong evidence for melasma and PIH, and is one of the safest options for darker skin tones and during pregnancy.

Kojic acid (1–4%) is derived from fungi and is another tyrosinase inhibitor with good tolerability. Often paired with other actives for additive effect.

Vitamin C (L-ascorbic acid) works via multiple pathways: antioxidant activity that prevents UV-triggered melanin production, and direct interference with melanin synthesis. Most effective as a preventative and for mild to moderate PIH.

Tranexamic acid (2–5%) is a relative newcomer with impressive clinical data, particularly for melasma. It works by blocking the interaction between keratinocytes and melanocytes that triggers excess melanin production. Available topically and (prescription) orally.

Niacinamide (5–10%) doesn't inhibit melanin production, but does inhibit its transfer to keratinocytes, effectively reducing the amount of pigment that reaches the skin surface. A versatile supporting ingredient.

Sun protection is the foundation, not optional

Any pigmentation treatment will be undermined without diligent, daily SPF use. UV exposure perpetually restimulates the melanocytes you're trying to quieten. Broad-spectrum SPF 50, reapplied every two hours during sun exposure, is the baseline. For melasma specifically, physical blockers (zinc oxide, titanium dioxide) are preferred as they also protect against the visible light that can trigger this condition.

Patience, expectations, and when to see a professional

Epidermal pigmentation can take 3–6 months to meaningfully improve with consistent topical treatment. Dermal pigmentation (as in deep melasma) may require professional intervention: chemical peels, laser (with care in darker skin tones), or oral tranexamic acid. If OTC treatments aren't moving the dial after three to four months, a dermatologist consultation is worthwhile.

All content on the ae skincare blog is for informational purposes only and does not constitute medical advice. For persistent or complex skin concerns, we recommend consulting a dermatologist.