Hyperpigmentation: Is It Fading? A Sunscreen and Monthly Photo Log

Item	Detail	Basis
How much to apply	SPF is measured using 2 mg per cm². Most people apply only 1/4 to 1/3 of that, so protection drops to about 1/4	Korean Dermatological Association, sunscreens · society
How often to reapply	Apply 20 to 30 minutes before outdoor activity and reapply every 2 to 3 hours. The association suggests about SPF 15 for daily life and SPF 30 or higher outdoors	Korean Dermatological Association, sunscreens · society
When to judge	Melasma takes at least 2 months to show a response and needs 6 months or more	Korean Dermatological Association, melasma · society
How often to compare	A trial of two groups with dark marks after acne (60 and 63 people) got different results at 12 and 24 weeks	2024 PMID 38685118 · A
Habits to log	Too much sun and squeezing or scratching were named as risk factors	2021 PMID 34880967 · B

When can you start judging whether a mark is fading?

Don’t judge after a week or two. Wait at least two months and compare photos taken a month apart. The Korean Dermatological Association says melasma takes at least 2 months to show a response and needs a care period of 6 months or more.

The conclusion can even flip depending on when you look. In a 2024 randomized trial that split patients aged 13 to 35 with dark marks after acne into two groups (60 and 63 people) and followed them for 24 weeks, the overall severity score differed clearly between groups at 12 weeks but was similar by 24 weeks. That’s why this guide’s log has columns at 1, 2, 3 and 6 months.

How much sunscreen should you use, and how many times a day?

More than you think, and on days you’re outside for a long time, reapply every 2 to 3 hours. According to the Korean Dermatological Association, SPF is measured by applying 2 mg per cm² (about 30 ml, or roughly 1 ounce, for the whole body), but people actually apply only 1/4 to 1/3 of that, so they get only about 1/4 of the protection.

A 10-minute walk to school and a half-day weekend outing are different conditions. In Korea, the association suggests about SPF 15 for everyday life and SPF 30 or higher for outdoor activities, and its melasma guidance calls SPF 30 or higher desirable. On days with a lot of sun time — a lunchtime walk, a desk by the window, driving — marking how many times you reapplied makes it easier to match against next month’s photo.

Why do marks last for months after you squeeze a pimple?

Squeezing or scratching has been reported to increase dark marks after acne, and once color is left behind, it fades on a timescale of months. In a 2021 observational study that pooled data from acne patients, 80% or more had dark marks after acne, and risk factors were being female, darker skin tone, severe acne, too much sun, and squeezing or scratching.

That study included many people with darker skin types, so its rates can’t be applied the same way to everyone. Still, if you log the days you touched your face and the days you spent a long time in the sun separately, you can see which one lines up with the spots that darkened in your photos.

With marks and new pimples at the same time, where should your routine focus?

Focus on sticking to three things every day — cleanser, moisturizer and sunscreen — and get new pimples managed separately by a dermatologist. In the 24-week trial above, both the group that used a prescription topical medicine and the group that didn’t used these three skin care steps throughout, and participants said the skin care helped reduce irritation and keep them on track.

A 2021 study that used sunscreen together with a moisturizing cream also reported less UV-induced redness and pigment change (the number of participants isn’t given in the abstract). In a 2026 trial, 20 people with darker skin types applied a finished sunscreen for 20 days, and on day 8 the pigmentation score where it was applied was about 30% to 53% lower than on untouched skin. Both studies tested finished formulas, so neither result can be credited to any single ingredient.

Monthly photo and sunscreen log

Point in time	Photo conditions	Days with sunscreen / days reapplied	Days with a hat or umbrella	Days you squeezed or picked	New pimples	Mark color vs. baseline
Start date	e.g., 9 a.m., living room window, arm’s length	—	—	—	___	Baseline photo
1 month	Same as start	___ / ___ days	___ days	___ days	___	Darker / similar / lighter
2 months	Same as start	___ / ___ days	___ days	___ days	___	Darker / similar / lighter
3 months	Same as start	___ / ___ days	___ days	___ days	___	Darker / similar / lighter
6 months	Same as start	___ / ___ days	___ days	___ days	___	Mark whether you need a visit

Take photos of your bare face with phone filters and retouching turned off. If you had a week with a lot of sun — a summer vacation, a school field day, a hike — leave a note next to that month.

When does a dermatologist need to see the marks?

• If your same-conditions photos show the color unchanged or darker after 6 months, bring your log to a dermatologist.
• If a mark spreads and gets bigger, or looks like a spot with an uneven shape or border, have a dermatologist check it.
• If new pimples keep coming up and leaving a mark each time, it’s better to get the acne itself managed by a dermatologist first.
• If wide patches across both cheeks darkened during a pregnancy or while taking birth control pills, it may be melasma, so consider an appointment.

Where these facts come from

• According to the Korean Dermatological Association’s sunscreen guidance, SPF is measured at 2 mg per cm², but people actually use 1/4 to 1/3 of that, so apply sunscreen generously and reapply every 2 to 3 hours.
• A 2024 phase 4 trial (PMID 38685118) followed two groups with dark marks after acne (60 and 63 people) for 24 weeks; both used a cleanser, moisturizer and sunscreen, and the difference in overall severity score was clear only at 12 weeks.
• In a 2026 randomized trial of 20 people with darker skin types (PMID 41240206), the pigmentation score on day 8 was about 30% to 53% lower where sunscreen was applied than where it wasn’t.