I've dealt with PIH from acne for most of my adult life. Dark marks that would sit there for months after a spot cleared, sometimes longer. The marks always bothered me more than the actual breakouts. Here's what I've found that actually shifts them.
Types
PIH -- the kind I know best -- is the dark mark left after inflammation. Acne, a picked spot, a rash -- anything that triggers inflammation. Skin with more melanin tends to produce more pigment in response.
Sun spots come from cumulative UV exposure. Flat, brown, mostly on the areas that see the most sun. They get darker without protection and don't go anywhere on their own.
Melasma is harder to manage than the other two. Forehead, cheeks, upper lip -- usually those areas. Hormonal trigger -- pregnancy, contraceptives. Get it under control and a few unprotected days in the sun can set it off again.
What I Use
SPF has to come first. UV triggers melanin production every day. No brightening ingredient can outwork unprotected sun exposure.
For the actual brightening work, I rely on a few things that act through different pathways. Niacinamide is the one I've had longest -- it blocks the transfer of pigment into surrounding skin cells, gentle enough for daily use, and it stacks well with everything else. I added tranexamic acid after I started getting some hormonal patches. It works differently -- it interrupts the signal between cells that starts melanin production in the first place. Both daily.
The Ordinary Niacinamide 10% + Zinc The Inkey List Tranexamic Acid Serum
Alpha arbutin is what I reach for on post-acne marks and sun spots. It inhibits the enzyme that makes melanin, without the concerns that come with hydroquinone. Safe long-term. Azelaic acid I use when I'm also dealing with congestion -- it targets overactive melanocytes and is anti-inflammatory, which makes it genuinely useful when the two problems overlap.
The Ordinary Alpha Arbutin 2% + HA Paula's Choice Azelaic Acid Booster
Vitamin C goes on in the morning under SPF. I find it better at preventing new spots than fading old ones. A retinoid a few nights a week handles cell turnover -- moves pigmented cells to the surface faster, shortening how long each mark sits. If you're newer to retinoids, the retinol beginner guide is worth reading first.
TruSkin Vitamin C Serum Differin Adapalene Gel 0.1%
Glycolic acid a couple of evenings a week, in support -- helps things shed and penetrate.
The Ordinary Glycolic Acid 7% Toning Solution
Routine
I keep the morning simple -- vitamin C, niacinamide, moisturiser, SPF. The SPF doesn't get skipped.
Evenings I cleanse, sometimes a glycolic or lactic toner, then one of my actives -- tranexamic acid, alpha arbutin, or azelaic acid, whichever I'm rotating -- then retinoid, moisturiser.
One thing at a time, spaced a few weeks. A compromised barrier won't absorb any of this properly -- and you can't tell what's working if you start five things at once.
Timelines
Fresh PIH -- marks from the last few months -- usually shifts in 8-16 weeks if you're consistent. Older marks that have been sitting for a year or more take 4-6 months minimum.
Sun spots are similar -- usually 3-6 months. Old, stubborn spots sometimes need a peel or laser on top.
Melasma takes the longest. Six to twelve months at minimum, and you're not curing it -- you're managing a condition with an ongoing trigger. Hormonal changes and unprotected sun can bring it back within days.
See a Derm If
Melasma not budging after 3-4 months on topicals. Pigmentation that looks unusual in shape or distribution. If you want to add laser or prescription treatments. If you have a deeper skin tone and are considering hydroquinone -- the risk calculation warrants professional input.
FAQs
Why isn't it fading?
Usually the SPF. UV kicks off melanin production every day -- without it, nothing else gets traction. After that, not enough time, or the wrong ingredient for the type. Melasma and PIH don't respond to the same things.
Vitamin C or niacinamide?
Both if you can. They do different things. If it's one or the other, niacinamide -- gentler and works across more issues.
Budget options?
Yes. Niacinamide, alpha arbutin, and azelaic acid are all available effectively for under £15. A basic SPF 30 is as protective as an expensive one. SkinCeuticals vitamin C and prescription tretinoin are upgrades, not requirements.