By Gemifys
Post-inflammatory hyperpigmentation (PIH) — those stubborn brown or dark patches that linger after acne, irritation, or years of sun exposure — is one of the most common reasons people stick with a tretinoin routine for months or years. It’s also one of the most common places where progress seems to stall: the marks fade for a while, and then… they just don’t get any lighter, no matter how consistent the routine is.
If that sounds familiar, you’re not doing anything wrong. Pigmentation that plateaus partway through treatment is a well-documented pattern, and there are a few reasons it happens — along with some evidence-based next steps worth discussing with a dermatologist.
Why hyperpigmentation can stop responding
According to the American Academy of Dermatology (AAD), dark spots can take many months to fade even with consistent treatment, and some pigment — particularly pigment that has settled deeper in the skin (dermal, rather than just epidermal) — responds much more slowly to topical treatments like tretinoin and azelaic acid than more superficial discoloration does. This is sometimes described as the difference between epidermal and dermal melasma-type pigmentation, and it’s a large part of why two people using the same routine can see very different results.
Ongoing sun exposure is another major factor. AAD guidance on sun protection and pigmentation notes that even brief, unprotected sun exposure can re-trigger melanin production in areas that are already prone to it, effectively resetting progress — which is why daily broad-spectrum sunscreen is considered a non-negotiable part of any hyperpigmentation routine, not an optional add-on.
What tends to help when progress stalls
- Reassess sun protection first. The Mayo Clinic notes that consistent, daily use of broad-spectrum SPF 30+ is one of the few interventions with strong evidence for both preventing new pigmentation and helping existing pigmentation fade over time.
- Layer in an antioxidant. Topical vitamin C has some research support for brightening and evening tone when used alongside routines like tretinoin and azelaic acid, per a review in the Journal of Clinical and Aesthetic Dermatology, though results vary by formulation and individual skin.
- Give it more time — but set a checkpoint. The AAD notes that fading dark spots can realistically take 6 to 12 months of consistent treatment. If there’s been no visible change over a couple of months despite good adherence, that’s a reasonable point to loop in a dermatologist rather than just continuing to wait.
- Ask about in-office options. For pigmentation that has plateaued on topicals alone, dermatologists may discuss options such as chemical peels or certain laser/light-based treatments. These carry their own risk profile (including, ironically, the risk of triggering more pigmentation in some skin types) and should only be pursued under professional guidance.
A note on routine complexity
Combining azelaic acid and tretinoin, as many people do, is generally considered reasonable by dermatologists, but stacking multiple active ingredients can sometimes cause low-grade irritation that itself contributes to pigmentation (a cycle sometimes called “irritation-induced PIH”). If a routine includes several actives, a dermatologist can help identify whether any of them might be working against the goal rather than for it.
This article is for general education only and is not a substitute for personalized medical advice. If hyperpigmentation isn’t improving despite a consistent routine, or if you’re unsure which ingredients are right for your skin, please consult a board-certified dermatologist — they can assess your specific skin and history and recommend next steps that are appropriate for you.
