Photoaging is driven by cumulative UV exposure. UVA and UVB cause DNA damage and oxidative stress in keratinocytes and melanocytes, leading to upregulated melanin production and irregular distribution—visible as sunspots, mottled tone and sometimes actinic lesions. 

Post-inflammatory hyperpigmentation (PIH) occurs when inflammation (e.g., acne, eczema, procedures) triggers cytokines and mediators that stimulate melanocytes to overproduce melanin or release it abnormally into surrounding keratinocytes.

Variations

• Epidermal vs dermal pigment: epidermal pigment (more superficial) is usually easier to treat.

• Skin phototype: darker skin has more reactive melanocytes and is more prone to PIH and rebound.

Severity & treatment approach

• Mild: topical pigment modulators + sun protection; light peels, gentle IPL/laser when appropriate.

• Moderate: combination of topicals, chemical peels, procedural treatments (IPL, microneedling/RF) and strict photoprotection.

• Severe/relapsing or melasma-like patterns: more cautious, slower protocols; lower-energy or fractionated devices plus conservative peels, always anchored in long-term topical and lifestyle management to avoid rebound.