PIH treatment doesn't stall because the actives aren't strong enough. It stalls because the protocol was built without the assessment that should precede it.
I see this consistently. A client arrives having used a tyrosinase inhibitor for four months with no visible change. The inhibitor was clinically appropriate. The protocol was not, because nobody confirmed the depth of the pigment, the Fitzpatrick type, or whether the underlying inflammation was still active. Starting treatment before those questions are answered is working downstream of the actual problem.
What PIH Is and Why It Matters for Protocol Design
Post-inflammatory hyperpigmentation is melanin deposition following an inflammatory episode in the skin. The inflammation triggers melanocytes to overproduce melanin, which transfers to keratinocytes and deposits in the epidermis. In some cases, particularly in darker Fitzpatrick types and following severe or prolonged inflammation, the pigment drops into the dermis.
Dermal PIH is significantly harder to treat than epidermal PIH. It responds more slowly to topical agents and may require device referral. The depth of the pigment is the first variable the protocol needs to account for.
The Davis and Callender 2010 review remains a key clinical reference on PIH epidemiology and treatment, particularly in skin of colour. The key documented finding: in Fitzpatrick III to VI skin, PIH is more common, more severe, and more persistent. Treatment thresholds, product concentrations, and timelines need to reflect this.
Assessing Pigment Depth Before Building the Protocol
The first clinical question is: where is the pigment?
Epidermal PIH reads as a well-defined, brown or tan mark. Under Wood's lamp examination, epidermal melanin is accentuated, because UV light increases the contrast between pigmented and non-pigmented skin. Dermal PIH reads as blue-grey under normal lighting and does not enhance under Wood's lamp in the same way, because the depth of the melanin diffuses the UV effect.
The practical assessment at consultation:
- Wood's lamp examination. Epidermal PIH accentuates. Mixed or dermal PIH does not. This changes the protocol.
- Fitzpatrick typing. Do this at the first consultation, not as an afterthought. The protocol appropriate for Fitzpatrick II is not appropriate for Fitzpatrick V. Using high-concentration actives without adjusting for skin type risks causing new PIH from the treatment.
- Age of the mark. Fresh epidermal PIH, a few weeks old, is more amenable to topical treatment than pigment deposited months or years ago.
- Status of the underlying trigger. PIH from acne that is still active cannot clear while new inflammation continues. The underlying condition is the primary clinical problem. The PIH is its consequence.
Building the Protocol: The Sequence That Matters
Control the trigger first. For PIH from acne, the protocol does not start with actives. It starts with managing the acne. NICE Clinical Knowledge Summaries on acne vulgaris are explicit that post-inflammatory pigment changes continue while ongoing inflammation occurs. A tyrosinase inhibitor applied to actively inflamed skin is running against the mechanism it is trying to interrupt.
SPF every day. This is step two in the sequence because without it the protocol cannot work. UV exposure re-stimulates the melanocytes responsible for the pigmentation. A client applying a tyrosinase inhibitor without daily SPF is working against the cause simultaneously. Broad-spectrum SPF 50, every morning, reapplied at midday in summer, is the foundation the rest of the protocol depends on. The NICE Clinical Knowledge Summary on melasma identifies photoprotection as central to management of acquired pigmentation for the same reason.
Tyrosinase inhibition. The primary topical target is the enzyme tyrosinase, the rate-limiting step in melanin synthesis. The strongest evidence supports azelaic acid (15 to 20 per cent), alpha arbutin, kojic acid, and tranexamic acid. For Fitzpatrick III to VI skin, azelaic acid is often the first-line choice: it has consistent evidence across skin types and a lower risk of paradoxical PIH than more aggressive inhibitors. Hydroquinone is effective but not first-line in higher Fitzpatrick types due to the risk of ochronosis with prolonged use.
Retinoids to accelerate turnover. Topical retinoids speed keratinocyte turnover, shedding pigmented cells faster than melanocytes can replace them. The evidence for tretinoin and adapalene in PIH is consistent. For practitioners without prescribing authority, retinol formulations have a role but a slower timeline. The combination of tyrosinase inhibitor plus retinoid is more effective than either alone.
Exfoliation, cautiously. Low-concentration AHAs support cell turnover and improve penetration of inhibitors. This is not a step to introduce until the client is tolerating the earlier steps without sensitivity. Irritation from an over-aggressive exfoliation triggers inflammation and can produce new PIH from the treatment. Less is more at this stage.
Timelines and Client Communication
NICE Clinical Knowledge Summaries are explicit that pigment changes from post-inflammatory causes are slow to resolve. The realistic timeline for epidermal PIH with a well-built protocol is twelve to twenty-four weeks. Dermal PIH takes longer and may require fractional resurfacing referral to achieve meaningful clearance.
Set this expectation explicitly at the consultation, and document it. A client who expects visible change in four weeks will conclude the protocol failed at week six. A client who understands the mechanism, knows why SPF is the foundation, and has a realistic twelve to twenty-four week timeframe will stay with the protocol and maintain it between appointments.
The single most common cause of protocol abandonment is not the product choice. It is an expectation that was never set correctly at the outset.
When to Refer
Refer to a dermatologist or specialist pigmentation clinic when:
- Dermal PIH is suspected and topical treatment has not produced a response after sixteen to twenty-four weeks.
- The pigmentation has features outside post-inflammatory change: irregular borders, colour variation within the mark, papular surface, or rapid change. Consider melanocytic lesions or other diagnoses.
- The client has Fitzpatrick V to VI skin with extensive PIH. Treatment-induced PIH from overly aggressive protocols is a documented risk in this population, and specialist input protects the client.
- Device referral for dermal PIH is indicated and sits outside your scope.
A confident referral is not a loss. It is the clinical step that protects the client and protects your reputation as a practitioner who knows the boundaries of what topical treatment can achieve.
For the full consultation framework, ingredient-by-ingredient breakdown by Fitzpatrick type, and treatment sequencing for post-inflammatory and acquired hyperpigmentation, Hyperpigmentation Decoded covers the assessment process and protocol design in the depth aesthetic practice requires.