Aesthetics

Chemical peels: superficial, medium and deep

A chemical peel is a controlled chemical wound, and the depth of that wound decides everything else. A superficial peel stays inside the epidermis and heals in 1 to 7 days, a medium peel destroys the full thickness of the epidermis and reaches the upper dermis over 7 to 14 days, and a deep peel taken to the mid reticular dermis needs 14 to 21 days of healing and total sun avoidance for 3 to 6 months. Depth also sets the acid, the concentration, the pigment risk and, under the proposals for England, who is allowed to do it at all.

What peel depth actually means

Every peel works the same way: a caustic agent denatures protein, the damaged layer separates and the tissue underneath repairs itself. What separates a 20 minute appointment from a fortnight indoors is how far that damage is taken. Light peels cause a localised injury inside the epidermis. Medium peels pass through the full thickness of the epidermis and the papillary dermis into the upper reticular dermis. Deep peels reach the mid reticular dermis, and taken past that they scar.

Depth is not printed on the bottle. It follows from the agent, its concentration, the number of passes, the contact time and how the skin was prepared. Concentration and contact time trade against each other, and 3 layers of a superficial acid are not the same as 1 pass of a medium strength one.

Practitioners read depth as it happens by watching the frost, the whitening that follows denaturation. Level 1 frosting is patchy with mild redness and belongs to a light peel. Level 2 is an even white coat over visible redness and marks a medium peel. Level 3 is a solid white plaque with almost no redness showing through, and that is a deep peel. Anyone who cannot describe the endpoint they are aiming for is not controlling depth.

The acids behind each depth

Very light peels use 10 to 20 percent trichloroacetic acid, low strength glycolic or salicylic acid, or retinoic acid. Light peels use 20 to 30 percent trichloroacetic acid, Jessner's solution or 30 to 50 percent glycolic acid, and reviews add 10 to 30 percent lactic acid, 40 percent mandelic acid and 30 percent salicylic acid. Jessner's solution is a fixed recipe of 14 g salicylic acid, 14 g resorcinol and 14 g of 85 percent lactic acid made up to 100 mL with ethanol.

Medium depth is usually reached by combination rather than by one strong acid. Jessner's solution or 70 percent glycolic acid goes on first and 35 percent trichloroacetic acid follows, which reaches the depth of the older 50 percent trichloroacetic acid peels with fewer dyschromias and scars. Neither first coat is a medium peel on its own. The English licensing consultation describes medium peels as trichloroacetic acid between 35 and 50 percent, sometimes with glycolic, pyruvic or salicylic acid. Glycolic acid keeps working until it is neutralised with 5 percent sodium bicarbonate or cool saline, while salicylic acid is neutralised by the skin's own lipoproteins.

Deep peels mean trichloroacetic acid above 50 percent, or phenol with croton oil. The classic formula blends 88 percent phenol with soap, croton oil and water to a working strength near 50 to 55 percent. Croton oil is the epidermolytic agent and the main driver of depth. Because phenol is absorbed, the face is treated one small section at a time, each taking about 15 minutes.

Downtime, sessions and the first fortnight

A superficial peel heals in 1 to 7 days. The skin is red, and once the redness settles a fine scaling can run for another 3 to 7 days. Makeup usually goes back on the same day or the next, and the surface is fully re-epithelialised within 7 to 10 days. Because each pass is shallow, they are sold as a course, and 3 to 5 peels every 2 to 5 weeks is a common plan.

A medium peel takes 7 to 14 days. The skin is red and swollen, swelling gets worse for the first 48 hours, eyelids can puff, blisters may form and break, and the crust lifts over 7 to 14 days. Antiviral tablets are usually taken for 10 to 14 days and camouflage makeup becomes possible after 5 to 7 days.

A deep peel is surgery in all but name. It is done under general anaesthesia in a surgical setting, the area is bandaged, and healing runs 14 to 21 days with 4 to 6 soaks a day and ointment for the first 14 days. Re-epithelialisation does not begin until day 3 or 4 and continues for 14 days or longer, and most people plan 2 to 3 weeks at home. Redness lasting months is a recognised outcome, a deep peel is done once and not repeated, and no result is permanent because skin keeps ageing.

Who should not have one

Some rules apply at every depth. Active infection in the treatment field, an open wound, a known allergy to the agent and current isotretinoin all stop the appointment. For medium and deep peels the list grows: isotretinoin within the past 6 months, pregnancy or breastfeeding, psoriasis, atopic dermatitis, rosacea in flare, connective tissue disease, poor wound healing, recent facial surgery or resurfacing, uncontrolled diabetes, immunosuppression, long term glucocorticoid use, smoking, previous radiotherapy to the area and any tendency to keloid scarring.

Cold sores matter more than people expect, because a peel hands the virus an open field. A history of herpes simplex is not a bar, but antiviral cover starts 1 to 2 days before the peel and runs until the skin has closed, generally 10 to 14 days. Mention isotretinoin even if you stopped years ago, and name every previous procedure on the face, including anything that damaged the skin barrier recently.

Phenol carries its own list. It is absorbed through the skin, it is highly arrhythmogenic, it is processed by the liver and cleared by the kidneys, so a cardiac arrhythmia or liver or kidney disease rules it out. One review reports cardiotoxicity or arrhythmia from that absorption in 34 to 50 percent of people given a phenol peel, so heart and blood pressure monitoring during the procedure, intravenous fluids and liver and kidney function tests beforehand are not optional. If you are pregnant, nothing deeper than a superficial peel belongs on the table, and the proposed English scheme sets a minimum age of 18 for the procedures it covers.

Pigment, sun and who may work at which depth

Light peels are considered suitable across all 6 Fitzpatrick skin types, but depth and pigment do not mix. Types 3 to 6 carry a higher risk of post-inflammatory hyperpigmentation and patchy colour, and a history of raised scarring raises it further. That argues for a practitioner who treats darker skin every week, not against peels. Pigment also goes the other way: medium and deep peels can leave skin permanently lighter, and on darker skin treated without that experience the colour change can be permanent. A pre-peel plan of 2 to 4 weeks, often tretinoin 0.025 to 0.05 percent, makes depth more predictable, and 2 to 4 percent hydroquinone before and after is used where pigment is the main concern. Much of the published evidence comes from small split face studies at single centres, and before and after photographs are not evidence.

Sun protection afterwards is part of the treatment, and direct sun is avoided completely in the first days, with sunscreen and a wide brimmed hat for weeks to months. After a medium peel that means total avoidance until the skin has healed. After a deep peel the standard instruction is total sun avoidance for 3 to 6 months, then daily sunscreen. Tanning beds, picking at scabs and makeup applied before the skin closes work against the aftercare, and infection follows from ignoring it. Our guide on how much sunscreen the face needs covers the amount.

Who may work at which depth is still being settled. The 2023 consultation on licensing non-surgical cosmetic procedures in England proposed 3 tiers. Superficial peels that destroy only viable epidermis sit in green, open to any licensed practitioner meeting agreed standards. Medium peels sit in amber, where a practitioner who is not a regulated healthcare professional needs oversight from a named one. Deep and phenol peels sit in red, restricted to regulated healthcare professionals in premises registered with the Care Quality Commission. It closed on 28 October 2023 and is not yet law, so the register you check and the questions you ask still do the work.

What to settle before you book

Frequently asked

How do I know which depth I am being sold?

Ask for the agent, the concentration and the number of passes, and ask which layer of skin it is meant to reach. Superficial peels stop in the epidermis, medium peels are typically 35 to 50 percent trichloroacetic acid into the upper dermis, and deep peels use phenol.

How long before I look normal again?

Roughly 1 to 7 days after a superficial peel, 7 to 14 days after a medium peel and 14 to 21 days after a deep peel. Redness can persist for months after the deeper two, and that is expected rather than a complication.

Can I have a peel if I have taken isotretinoin?

Not while you are on it. Use within the past 6 months is a reason to avoid medium and deep peels, so tell the practitioner even if you stopped years ago.

Are peels safe on darker skin?

Light peels are considered suitable for all 6 Fitzpatrick types, but types 3 to 6 have a higher risk of post-inflammatory hyperpigmentation, and medium and deep peels can also leave the skin permanently lighter. Choose a practitioner who treats darker skin routinely and expect a priming plan of 2 to 4 weeks.

How strict is the sun rule?

Strict. Direct sun is avoided completely for the first days at any depth, a medium peel needs total avoidance until the skin has healed, and a deep peel needs total sun avoidance for 3 to 6 months before daily sunscreen takes over.

Can I do one at home?

Peels sold for use at home have caused serious injuries, and in the United States the Food and Drug Administration advises buying and using a peel only under the supervision of a licensed, trained provider such as a dermatologist. Depth is the one thing you cannot judge on your own face.

Sources

• Chemical Peels, StatPearls · Peer reviewed reference chapter hosted by the National Library of Medicine; source for the depth classification, the agents and concentrations at each depth, frosting levels 1 to 3, priming with tretinoin and hydroquinone, the contraindication lists including isotretinoin within 6 months, and post-peel sun advice.
• A practical approach to chemical peels, a review of fundamentals and a step by step protocol · Journal of Clinical and Aesthetic Dermatology review via PubMed Central; source for the lactic, mandelic and salicylic acid concentrations, the Jessner's solution recipe, the combination medium peels of 70 percent glycolic acid or Jessner's solution with 35 to 50 percent trichloroacetic acid and their wider safety margin, re-epithelialisation of 7 to 10 days superficial and from day 3 or 4 after a deep peel, antiviral cover started 1 to 2 days before and run for 10 to 14 days, and the report of cardiotoxicity or arrhythmia in 34 to 50 percent of phenol patients.
• Chemical peels, frequently asked questions · American Academy of Dermatology patient information; source for healing of 1 to 7, 7 to 14 and 14 to 21 days, the course of 3 to 5 peels at 2 to 5 week intervals, the 2 to 4 week pre-peel plan, the 48 hour swelling peak, makeup after 5 to 7 days and at least 14 days, the 4 to 6 daily soaks and 14 days of ointment, general anaesthesia for a deep peel, a deep peel being performed only once, persistent redness for months, lighter skin colour after medium and deep peels, and the 3 to 6 months of sun avoidance after a deep peel.
• Chemical peels, overview · American Academy of Dermatology overview; source for what peels are used to treat and for the United States Food and Drug Administration warning it carries, that some peels sold for use at home are causing serious injuries and a peel should be bought and used only under the supervision of a licensed, trained provider.
• The licensing of non-surgical cosmetic procedures in England, consultation document · Department of Health and Social Care consultation that closed on 28 October 2023; source for the green, amber and red tiers, the definitions of superficial, medium and deep peels, the monitoring requirement for phenol and the proposed minimum age of 18.

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This guide is for general information. It does not replace advice from a dermatologist, physician or qualified practitioner, or an examination.