What is the difference between a medium and a deep peel?
Depth is the difference. A 2018 review by Stanford dermatologists divides peels by how far the wound goes: superficial peels stay in the epidermis, medium-depth peels take in the whole epidermis and the upper part of the dermis (the papillary dermis), and deep peels reach the middle of the dermis. The depth depends on the chemical, its strength, how many layers are applied and the skin itself, and it rises with the cumulative dose. That is why the same acid can sit in more than one band. The page on chemical peels in Malaysia sets out the three bands and the superficial peels, so this article stays with the two deeper ones.
For medium-depth peels the review names 35 to 50% TCA, or 70% glycolic acid, usually after a primer such as Jessner solution or solid carbon dioxide. For deep peels it names the Baker-Gordon formula: phenol diluted to 50 to 55%, with croton oil to break down the surface and a detergent. Pure phenol on its own acts only to medium depth, because it forms a plug of denatured protein that stops it going further.
What does a TCA peel do, and what is the downtime?
TCA (trichloroacetic acid) is the usual medium-depth agent. DermNet NZ gives its concentration as usually 20 to 35% and describes the treatment as painful, with swelling, redness and crusting for the next week or so. It can improve skin texture, blotchy pigment, freckles and sun-damage spots. Fine wrinkles and some acne scars look less obvious afterwards, but it has no effect on deep furrows.
The 2018 review adds the timeline. Redness intensifies and peaks at 4 to 5 days, and exfoliation is complete in 10 to 14 days. It lists fine lines, sun damage, superficial pigment such as melasma, and superficial acne scars as the uses. DermNet NZ advises waiting 3 to 6 months before repeating a moderate-depth peel.
Strength matters. The review says TCA above 50% as a single agent has fallen out of favour because of dark or pale marks, scarring and infection, and combining a primer with a lower strength (for example Jessner solution then 35% TCA) gave comparable results to the old 50% peel with a more even depth.
What does a phenol-croton oil peel do?
A phenol peel injures the skin to the middle of the dermis, and DermNet NZ describes it as effective for surface wrinkles and also for deep furrows, which a TCA peel does not reach. The skin afterwards is pale and smooth, sometimes waxy and mask-like. The 2018 review names moderate to severe sun-ageing with deep furrows as the setting where it was designed to be used.
The recovery is a wound. Within 24 to 48 hours the whole surface skin dies back, with oozing and crusting, the swelling can be severe enough to close the eyes, and new skin does not start to form until day 3 or 4 and continues for 14 days or longer. The review says a deep peel belongs in an ambulatory surgical setting, with sedation and intravenous fluids.
Both DermNet NZ and the review say deep peels are used far less than they were. The review notes that lasers have largely replaced them because a laser controls depth more precisely and avoids the toxicity of phenol.
What are the risks of these peels on Asian skin?
The risks rise with depth and with skin tone. DermNet NZ says peels are most often used in Fitzpatrick skin types I to III, and that types IV to VI have an increased risk of dyspigmentation (darker or paler patches), hypertrophic scars and keloids, so a peel must be done cautiously and with full consent. A 2018 review of peel patient selection puts it more firmly: avoid deep peels in skin types III to VI.
For medium-depth peels, the dark patch is the usual problem. In a small study from a dark-skinned population, 15 patients had Jessner solution followed by 35% TCA for acne scars. Nine had temporary post-inflammatory hyperpigmentation, all were free of noticeable pigment three months after the last peel, and those who stayed clear were of light brown complexion. Improvement was seen in all but one patient, yet only one reached more than 75% clearance, and the four patients with mainly pitted and deep scars did least well.
Phenol has a different pigment problem. A review of peels in Asians says it has rarely been used there because of hypopigmentation, a pale patch attributed to damage to the pigment cells or to deep scarring of the dermis. Its cutaneous effects also include hypertrophic and keloid scars and prolonged redness. Herpes simplex (a cold sore) can reactivate after a medium or deep peel, which is why a history needs treatment beforehand. The article on cold sores before peels, filler and lasers explains this.
Why does phenol need heart monitoring?
Because phenol is absorbed through the skin and reaches the circulation. The 2018 review calls it highly arrhythmogenic, meaning it can set off abnormal heart rhythms, and says it is broken down by the liver and excreted by the kidneys. For that reason it recommends sedation, intravenous hydration to lower the blood level, and cardiac monitoring, and says anyone with a history of heart rhythm problems, or liver or kidney dysfunction, should not have a phenol peel. DermNet NZ describes the heart rhythm disturbances as potentially fatal, and a review in Asians lists fatal arrhythmias, liver and kidney toxicity and breathing depression.
A table in the 2018 review lists cardiotoxicity or arrhythmia as seen in 34 to 50% of patients after a deep peel. It is a figure from a review table and not from a trial, and the reviewers do not say how severe those rhythm changes were, so it is a reason for monitoring and says little about the risk of a fatal event. TCA is different: it neutralises itself on the skin and is not absorbed into the bloodstream, even at high strength.
Who should not have a medium or deep peel?
A patient-selection checklist in the 2018 acne-peel review lists the reasons to wait or decline: current minocycline (it makes skin sensitive to light and raises the chance of dark patches), an active or past infection such as herpes simplex, radiation to the head or neck, a history of thick or keloid scars, a weakened immune system, major facial surgery in the past six months, unrealistic expectations, and pregnancy, which it says to avoid. The articles on keloid-prone skin and on treatments that wait during pregnancy cover two of these in more depth.
Isotretinoin is a debated item. The same review says there is a notion that people taking it should avoid medium and deep peels for 6 to 12 months, and also that a systematic review found insufficient evidence to delay peels; it concludes that doctor and patient must weigh the risk. For phenol, the heart, liver and kidney exclusions above are added.
Who is allowed to perform these peels in Malaysia?
Not everyone who can do a facial. The Ministry of Health guideline for registered medical practitioners restricts general practitioners to non-invasive and minimally invasive procedures. Superficial peels are listed as non-invasive, medium-depth peels as minimally invasive, and deep peels as invasive procedures, listed under dermatologists. DermNet NZ likewise says a dermatologist or plastic surgeon usually performs moderate to deeper peels.
The practical check is the same for any procedure: confirm the doctor on the MMC register and the credentialing for the procedure. The guide to who can perform aesthetic procedures in Malaysia explains the registers.
How is TCA CROSS for icepick scars different?
TCA CROSS (chemical reconstruction of skin scars) uses the same acid in a different way. A review in Asians describes applying 60 to 100% TCA with a sharp-tipped wooden applicator into the base of the scar, sparing the normal skin around it, so that repeated application thickens the dermis and lifts the scar. It treats individual scars and not the whole face, so there is no sheet of peeling skin.
The evidence is mostly small and open-label. In studies using 100% TCA on Fitzpatrick skin types IV and V, the authors reported excellent results in more than 70% and good in 20% after four sessions, with no scarring or lasting pigment change in the larger study, and one case each of temporary pale and dark patches in the pilot. In a split-face trial of 20 patients, CROSS and a fractional laser did not differ significantly for icepick scars, the laser did better for rolling scars, and CROSS left redness for longer. The practical reading is that the scar type decides the tool.
TCA CROSS is one of the acne-scar options at The Retreat Clinic, alongside subcision and filler as needed, chosen by scar type. The article on icepick, boxcar and rolling acne scars shows how the types are told apart and what each needs.
Why is a deep peel rarely the first choice?
Because the wound is large and the margin for error is small. The review says lasers have largely replaced deep peels, with lower rates of scarring, and DermNet NZ says phenol is rarely used on the face now. For a medium-depth peel, the question is whether the finding in front of the doctor is one that a milder, repeatable option cannot reach. A deeper wound is a bigger bet on healing well, and on Asian skin the chance of pigment change is why most reviews steer towards lighter options first.
