TL;DR
PIH is the dark mark left after skin heals from acne, insect bites, or heat rash; in Malaysia and Indonesia the intense UV and year-round humidity make these marks darker and slower to fade.
- Trigger
- Acne, scratches, mosquito bites, burns
- Why worse in tropics
- UV index 11–13 amplifies melanin after injury
- Skin type
- Fitzpatrick IV–V (most SEA skin) heals with more pigment
- Fade time
- 3–24 months without treatment
The direct answer
Post-inflammatory hyperpigmentation (PIH) is excess melanin deposited where skin was inflamed — most often after acne, a mosquito bite, or heat rash heals.
In tropical Malaysia and Indonesia, UV index routinely reaches 11–13, so any healing spot keeps receiving melanin-stimulating light, turning a faint mark into a stubborn dark patch.
Why it lingers in MY & ID
- Year-round high UV means almost no "low-sun" recovery window.
- High humidity drives more acne and fungal rashes, creating new inflammation cycles.
- Darker baseline skin (Fitzpatrick IV–V) has more active melanocytes, so pigment is both stronger and longer-lasting.
What shortens the fade
Daily broad-spectrum SPF 50+, stopping picking at spots, and a routine with tranexamic acid or niacinamide are the three levers that reliably speed clearance.
FAQ
Is PIH permanent?
No. PIH is excess pigment in the skin, not scar tissue. With sun protection and active ingredients it fades, though darker marks can take over a year.
Why are my marks darker after a holiday at the beach?
UV exposure after inflammation re-triggers melanin production in the healing area, deepening the mark. Strict sunscreen is essential during the fade.
Does skin tone affect PIH?
Yes. Fitzpatrick IV–V skin, common in Malaysia and Indonesia, produces more pigment after injury, so marks appear faster and last longer.