Reviewed November 11, 2026
Exfoliating Dark Spots: What Works on Post-Inflammatory Marks
Post-inflammatory hyperpigmentation is melanin left behind after inflammation, and it fades when you speed up the turnover of the pigmented cells while stopping new inflammation. Glycolic and lactic acid help, at low strength, two to three times a week, but they only work if you wear sunscreen every day, because UV darkens the mark faster than the acid fades it. The FDA warns that AHAs increase sun sensitivity during use and for one week after stopping, so the sunscreen is not optional, it is the treatment.
The dark mark a breakout leaves behind is not a scar. It is melanin, made in excess while the skin was inflamed, sitting in the top layers waiting to shed. That distinction matters, because a scar needs a different fix entirely, while a pigment mark responds to the most boring routine in skincare: gentle exfoliation, sun protection, and time.
The mistake is reaching for the strongest acid first. A high-strength glycolic peel on skin that just finished breaking out can trigger the exact inflammation that made the mark, and the mark comes back darker. The fix for pigment is slow and steady, which is the opposite of what the marketing promises, and the reason most people quit before it works.
Which acids help, and at what strength
Glycolic acid is the usual pick, because its small molecule penetrates well and speeds the shedding of pigmented cells. Lactic acid is the gentler alternative, and the better one for darker skin tones, because it carries a lower risk of triggering more pigment while it works. Start at 5 to 8 percent, two or three times a week, and only raise the strength if the skin stays calm for a month. The studies that showed improvement used 8 percent glycolic or lactic acid creams over 22 weeks, which is the timeline to expect, not two weeks.
Salicylic acid helps indirectly, by keeping new breakouts from forming, and no new breakout means no new mark. It does not fade an existing mark the way an AHA does. Use it for prevention, not for correction, and never layer it with a strong AHA on the same night. The two together strip the barrier faster than either one alone, and a stripped barrier makes pigment worse.
Why sunscreen is the actual treatment
UV light stimulates the same melanocytes that made the mark, so a pigmented spot exposed to sun without protection darkens faster than any exfoliant can fade it. This is the step people skip because it does not feel like treatment, and it is the step that decides whether the routine works at all. A broad-spectrum SPF 30 or higher, applied every morning and reapplied if you are outside, is the baseline.
The FDA's guidance on AHAs is specific: they increase sun sensitivity during use and for one week after you stop. That means the sunscreen matters even on the days you skip the acid. If you are not willing to wear sunscreen daily, do not start an acid for pigment. You will make the mark worse and blame the product.
The timeline, and when to stop
Expect visible fading in eight to twelve weeks, and meaningful fading in four to six months. That is slow, and it is honest. Pigment sits in layers, and each layer has to shed before the next one shows. Anyone promising a fade in two weeks is selling a peel strength that belongs in a clinic, not a bathroom.
Stop and see a dermatologist if the mark is raised, changing shape, bleeding, or has a border that looks different from your other marks. Most pigment marks are harmless, but a changing spot is not a cosmetic problem, and no exfoliant is the right answer for it. Also stop if the skin around the mark starts darkening instead of lightening, which is a sign the routine is causing the inflammation it was meant to fix.
Related reading
Two earlier posts on this site cover ground “Exfoliating Dark Spots: What Works on Post-Inflammatory Marks” builds on: AHAs and Sunscreen: Why the Photosensitivity Warning Is on the Label, How Often Should You Exfoliate? Frequency Is Set by Strength, Not by Habit, and Body Exfoliation for Keratosis Pilaris: The Arms-and-Legs Routine That Works.
Frequently asked questions
How long does it take for exfoliation to fade dark spots?
Expect visible fading in eight to twelve weeks and meaningful fading in four to six months, because pigment sits in layers that shed one at a time. Studies showing improvement used 8 percent glycolic or lactic acid creams over 22 weeks, so the timeline is months, not weeks.
Which acid is best for post-inflammatory hyperpigmentation?
Glycolic acid is the usual pick for its small molecule and penetration, while lactic acid is the gentler choice and better for darker skin tones, where stronger acids carry a higher risk of triggering more pigment. Start at 5 to 8 percent, two to three times a week.
Do I really need sunscreen when using acids for dark spots?
Yes, it is the treatment, not an extra. UV stimulates the melanocytes that made the mark, so an unprotected spot darkens faster than the acid fades it. The FDA warns AHAs increase sun sensitivity during use and for one week after stopping, so wear broad-spectrum SPF 30 or higher every morning.
Can exfoliating make dark spots worse?
Yes, if the exfoliant is too strong or used too often. Over-exfoliation causes inflammation, and inflammation triggers more melanin, which darkens the mark. If the skin around the spot starts darkening, stop the acid and let the barrier recover before trying a gentler strength.