Two instructions show up constantly in pre-treatment protocols, and read side by side they look like a contradiction.
The first: stop your retinoid before microneedling or a peel. The second: prime the skin with a retinoid before a peel, particularly in darker skin types.
Both are standard. Both are in wide clinical use. New practitioners tend to pick one, follow it consistently, and quietly assume the other camp is wrong. They’re not, and understanding why is the fastest route to a sequencing protocol that actually holds up.
The contradiction is a timescale problem
Priming and pausing operate weeks apart and do completely different jobs.
Priming happens in the weeks before treatment. A review of cosmetic procedures in patients with skin of colour describes it plainly: pretreatment conditioning with a melanogenesis inhibitor such as topical hydroquinone 4 percent twice daily, or a topical retinoid such as tretinoin, starting two to four weeks before the peel. The point is to get the melanocytes settled and epidermal turnover moving before you injure the skin on purpose. It is not a same-week intervention.
Pausing happens in the days before treatment, and its job is completely different: don’t arrive with a compromised barrier and active irritation on the day someone plans to create controlled injury.
So the sequence isn’t “retinoid or no retinoid.” It’s prime for several weeks, then pause for several days, then treat. Those two instructions were never in conflict. They were separated by three weeks, and the conflict only appears when you compress a protocol into two bullet points on an aftercare sheet.
The evidence behind these two instructions is very uneven, and it’s worth saying so. The priming side is reasonably well supported. The pausing side is mostly clinical convention: the published advice ranges from three days to two weeks with no strong trial behind any particular number, and most of what circulates online traces back to other clinics’ handouts rather than to data. Treat the pause window as a sensible precaution with a soft evidence base, not as a rule with a citation behind it. Our retinol calculator covers what a reasonable ongoing routine looks like by strength, which is the thing that actually determines how much of a pause a given client needs.
Depth: the variable that decides everything else
The most useful microneedling data of the last few years is a split-face design, because it removes the patient as a variable.
El-Domyati and colleagues ran a split-face comparative study published in the International Journal of Dermatology on 14 patients with atrophic post-acne scarring, treating one side at 2.5mm and the other at 1.5mm, six sessions at two-week intervals. The deeper side did significantly better, at p = 0.02, on both clinical and histological assessment.
That result is easy to over-read. It says deeper worked better for atrophic acne scars in that population. It does not say deeper is better generally, and running 2.5mm on someone booked for general skin quality is how you convert a low-risk treatment into a downtime problem, or worse in the wrong hands.
The counterweight is what 1.5mm alone achieves. An earlier objective evaluation from the same group, published in the Journal of Clinical and Aesthetic Dermatology, took ten patients at 1.5mm, six sessions at two-week intervals, and measured the tissue rather than asking people how they felt about it. Epidermal thickness went from 63µm to 80.2µm. Collagen type I reached 78.2 percent, type III 74.3 percent, newly synthesised collagen 19.5 percent, all statistically significant against baseline.
So 1.5mm is not a token depth. It produces measurable remodelling. The 2024 study says that for a specific indication you can do better by going deeper, not that shallower does nothing. Our microneedling depth calculator maps depth to indication and to the experience level a given depth actually requires, which is the second half of that decision and the half that gets skipped.
The 2015 study also pinned down the timeline, which is the thing most consultations get wrong: mild improvement at one month, good improvement at three. A client who expects visible change after session one isn’t being unreasonable. She’s been told something wrong, probably by a before-and-after photo with no timestamp on it, and correcting that belongs in the consult rather than in a disappointed message at week two.
Intervals: two weeks or four?
Both studies above used two-week intervals. Plenty of protocols use four. Neither is wrong, and the choice tracks depth more than anything else.
Shallower work at two-week intervals is well tolerated and is what the collagen data above came from. Deeper work needs the barrier to be genuinely back before you go again, and “genuinely back” is longer than “looks fine.” When practitioners get into trouble stacking sessions, it’s usually because the visible erythema resolved and got read as complete healing.
The peel literature leans longer. The sequential protocol described below used four-week intervals throughout, and for pigment-driven indications that spacing is doing real work: you’re waiting to see whether post-inflammatory pigmentation shows up before you decide what to do next. If the next session is already booked before you have that answer, the calendar is making the clinical decision.
Fitzpatrick changes the whole calculation
This is where sequencing stops being about efficacy and starts being about not causing the exact problem you were treating.
The background risk is genuinely large. Up to 92 percent of patients at Fitzpatrick IV and above develop post-inflammatory hyperpigmentation after ablative CO₂ resurfacing. That figure is for an aggressive modality, but it sets the direction: in higher phototypes, the pigment response to injury is the main event you are managing, not a footnote.
Superficial work is much safer, and it’s worth knowing by how much. The skin-of-colour review reports a complication rate of 3.8 percent for superficial peels across Fitzpatrick III to VI, with type VI most prone to side effects and complications resolving within eight months.
The most instructive recent data is a retrospective review published in the International Journal of Women’s Dermatology by Maruma and colleagues, covering 40 melasma patients who were 77.5 percent Fitzpatrick V, with type IV and VI making up the rest. The protocol ran progressive glycolic acid at 20, 30, then 40 percent from week 0 to week 8, followed by progressive TCA at 15, 30, then 40 percent from week 12 to week 20, at four-week intervals, with modified Kligman’s cream and SPF 50 started four weeks before the first peel.
The numbers:
- No scarring at all, across 40 patients at phototypes historically considered high risk for exactly that.
- Post-peel pigmentation changes in 12.5 percent for the glycolic phase and 32.5 percent for the TCA phase, all temporary and resolved within two to four weeks.
- Irritation in 77.5 percent (glycolic) and 95 percent (TCA), with burning near-universal.
- Melasma recurrence in 70 percent by twelve weeks after treatment stopped.
The headline is that high-concentration acids turn out to be survivable at phototypes historically treated as too risky for them, provided you spend four weeks priming first and step the concentration up rather than opening at strength. That proviso is doing all the work.
The pigmentation numbers deserve to be said out loud in a consultation rather than buried in a consent form, especially since TCA carried roughly triple the pigment risk of the glycolic phase. And then there’s the recurrence figure, which is the one I’d quote to anyone who thinks a peel series is a cure. Seventy percent, within twelve weeks of stopping. Melasma gets managed, not finished, and a protocol that ends at the last peel has quietly planned for relapse.
Our chemical peel calculator takes Fitzpatrick type and concern and shows where a given acid and depth land, including the ones you should route to a physician rather than perform. If your menu is drifting toward medium-depth work, it’s worth checking that against provincial scope rules too, which we cover in the med spa opening checklist and the pillar guide to running a profitable esthetics business.
Test spots
For medium-depth peels the skin-of-colour review suggests a test spot: a small volume of the exfoliating agent along the jawline or under the chin, one week before full-face treatment.
A week, not a day. The reaction you’re screening for is pigmentary, and pigment takes days to show. A test spot read at 24 hours tells you about immediate irritation and almost nothing about the risk you were actually worried about, which makes it a scheduling ritual rather than a screening test.
The order, end to end
Putting the evidence together into something you can put on a protocol sheet:
- Four weeks out. Start priming where indicated, particularly Fitzpatrick IV and up: a retinoid, a melanogenesis inhibitor, and daily SPF that the client actually uses. This window is not optional in higher phototypes, and it is the single highest-leverage step in the whole sequence.
- One week out. Test spot for medium-depth peels. Read it at a week.
- Three to seven days out. Pause retinoids and other exfoliating actives, scaled to the strength they’ve been using and the depth you’re about to go. Soft evidence, sensible precaution.
- Treatment day. Depth chosen from indication rather than from what the client asked for. Document what you actually did.
- Between sessions. Two weeks for shallower microneedling, four for deeper work and for anything pigment-driven where you need to see the PIH answer before committing to the next session.
- Reintroduction. Actives come back when the barrier is back, not when the redness has gone.
- Maintenance. Especially for melasma, where seven in ten recur within three months of stopping.
Charting it, because the protocol only exists if it’s recorded
All of the above assumes the next practitioner knows what the last one did. Frequently they don’t, because the record says “microneedling, tolerated well.”
The fields that make a series work are unglamorous: depth in millimetres, number of passes, areas treated, device, the pre-treatment instructions actually given, and what the skin did afterward. For peels: agent, concentration, number of coats, frost level if relevant, neutralisation, and downtime observed. Without depth and concentration in the record, there’s nothing to escalate from, and session four is a guess wearing a protocol’s clothes.
This is the same problem we’ve written about on the injectable side of charting, and the fix is the same: give the numbers their own fields instead of hoping they survive in a sentence. Zdrovia’s smart blocks put depth, concentration, and passes into structured inputs inside charting that still reads normally, so the next appointment starts from what was done rather than from what someone remembers. The pre-treatment side belongs on the intake form, and we’ve covered what that needs to capture in our guide to the esthetician client intake form.
The short version
- Priming and pausing are different instructions at different timescales, four weeks out versus a few days out, and they do not conflict.
- Priming has real support in higher Fitzpatrick types. The pause window is convention with thin evidence. Weight them accordingly.
- 1.5mm produces measurable collagen remodelling. Deeper beat shallower for atrophic acne scars specifically, not universally.
- Tell clients mild change at one month, good change at three. Session one is not a result.
- In Fitzpatrick IV and above, pigment is the main risk you’re managing. Prime, step concentrations up gradually, and test spot a week ahead for medium-depth work.
- Temporary pigmentation in roughly a third of TCA patients is a consent conversation.
- Melasma recurs in about 70 percent within twelve weeks of stopping. Plan maintenance from the start.
- Depth, concentration, and passes belong in structured fields, because you can’t repeat or adjust what you can’t reconstruct.
None of this requires new equipment. It mostly requires deciding your protocol in advance, writing down what you actually did, and resisting the urge to escalate on a schedule instead of on a skin response.