Sun protection after treatment in Busan Seomyeon, and why it decides the result.

Patients who report that a laser did not work have frequently undone it themselves in the four weeks afterwards. This is not a lecture — it is an explanation of the mechanism, so the instruction becomes something you understand rather than something you were told.

Why does sun matter more after treatment than before?

Because treated skin is primed to produce pigment. Any inflammation signals melanocytes to increase melanin production, and UV is itself a pigment trigger — so exposure onto skin that has just been lasered stacks two signals rather than one. The result is post-inflammatory hyperpigmentation appearing two to four weeks later, which then takes months to clear. This is the mechanism behind almost every case of a pigment treatment that appeared to fail — see PIH risk on Asian skin.

Which treatments need strict protection, and for how long?

Anything touching pigment or the epidermis. Pico toning and melasma treatment need it from the moment you leave and indefinitely for melasma specifically. Fractional resurfacing and acne scar work need it from the moment flaking stops, for at least four weeks and sensibly beyond. Mole removal sites need it until the pink has faded, which is two to three months.

Which treatments do not require it?

Botox, filler and energy lifting carry no pigment risk, because none of them injures the epidermis. Ordinary sun protection applies for ordinary reasons, but there is no treatment-specific window. Boosters sit in between — no pigment risk, but injection points benefit from a day or two of not being baked while they settle.

Is SPF50 enough on its own?

For UV, yes. For melasma and for pigment-prone skin, not quite — and this is the part most patients have never been told. Visible light, particularly the blue end, drives melanocyte activity independently of UV, and conventional chemical sunscreens do not block it. Tinted mineral formulations containing iron oxides do. If you are treating melasma or you are prone to PIH, a tinted mineral sunscreen is meaningfully better than a higher SPF number.

How much and how often?

More than people apply, and reapplied. The tested amount is roughly a teaspoon for the face and neck, which is considerably more than most people use, and reapplication every two to three hours of daylight exposure. Applying half the amount does not give half the protection — the relationship is worse than linear. This is duller advice than choosing a product, and it matters more.

Does winter change anything?

It reduces the requirement without removing it. UV is lower in a Korean winter but not absent, and visible light is unchanged year-round. Winter is genuinely the better season for pigment work and resurfacing for exactly this reason — less ambient UV, less sweat, easier compliance. Late autumn through early spring is when we would rather schedule a course if your travel allows it.

What if I am travelling somewhere sunny?

Then say so before treatment rather than after, because it changes the recommendation. Flying into strong sun days after pigment work is the worst available timing, and treating tanned skin on arrival is a contraindication rather than a caution. Where a sunny leg of the trip is unavoidable, we would rather move you to a treatment that does not depend on sun avoidance — boosters or lifting — than start something that will undo itself.

What happens if I slip up once?

Usually nothing dramatic. A single unprotected hour is not the same as four weeks of casual exposure, and the response is cumulative rather than triggered by one lapse. What causes problems is a pattern — skipping reapplication daily, or a beach day in the fortnight after treatment. If it happens, resume properly rather than concluding the course is ruined, and mention it at the next session so settings can account for it.

What else compounds the risk?

Heat independently of light, which surprises people. Saunas, hot yoga, cooking over a stove and hot showers directed at the face all raise skin temperature enough to stimulate pigment production — this matters most for melasma, where heat is a recognised trigger alongside UV and hormones. Patients who protect diligently from sun and sit in a jjimjilbang twice a week are working against themselves.