How chemical peels work
A chemical peel applies an acid solution to the skin to dissolve the bonds between cells and remove a controlled thickness of tissue. As that tissue is shed, the skin regenerates, and the deeper the peel, the more of the dermis is stimulated to remodel. The principle is centuries old; what has changed is the precision with which agents and concentrations are matched to a specific depth.
Depth is everything. It defines what the peel can treat, how long recovery takes, and how much risk it carries. Peels are therefore classified by how far into the skin they act, from superficial peels that affect only the epidermis to deep peels that reach the mid-dermis.
The variables a practitioner controls are the acid used, its concentration, the number of coats applied, and the contact time before neutralisation. Two clinics using the same named acid can deliver very different peels by changing these. That is why the name on the bottle tells a patient far less than the depth being targeted.
Skin preparation before the peel matters as much as the peel itself, particularly at medium depth and in darker skin. Priming the skin for a few weeks beforehand with agents such as a retinoid or a tyrosinase inhibitor can even out the response, reduce the risk of pigment disturbance, and improve the final result. A clinic that books a medium peel with no priming and no discussion of skin type is skipping a step that the evidence and the specialist literature treat as standard practice.
Superficial peels
Superficial peels act on the epidermis alone. The common agents are alpha-hydroxy acids such as glycolic and lactic acid, beta-hydroxy acid (salicylic acid), and low-concentration trichloroacetic acid.
These are the workhorses of skin maintenance. They improve dullness, mild pigmentation, congestion and the earliest fine lines, and they are the class most suited to a course of regular treatments. Salicylic acid, being oil-soluble, is particularly useful for oily and acne-prone skin. The trade-off is that a single superficial peel produces a subtle result; the benefit is cumulative across a course.
Downtime is minimal, typically some light flaking and redness for a few days. This is the class most people mean when they book a peel, and it is the safest across all skin types.
Because a single superficial peel does little on its own, these are best understood as a maintenance treatment rather than a one-off event. A course of several peels spaced two to four weeks apart, combined with a sensible home regimen, is where the value lies. Patients who expect a single superficial peel to transform their skin have been sold the wrong expectation, and the reasonable practitioner frames it as one part of an ongoing routine.
Medium-depth peels
Medium-depth peels penetrate to the upper dermis, most commonly using trichloroacetic acid at higher concentrations, sometimes combined with other agents to control the depth. They address moderate pigmentation, actinic damage, fine to moderate wrinkles and some acne scarring.
A medium peel is a genuine medical procedure with a genuine recovery period, not a lunchtime treatment, and it should be treated as such.
The result is more pronounced than a superficial peel, and so is the recovery. Expect several days of visible peeling, redness and crusting, with the skin looking worse before it looks better. This class sits at the point where practitioner experience starts to matter a great deal, because pushing a medium peel slightly too deep changes both the result and the risk profile.
Judging the endpoint of a medium peel is a genuine clinical skill. The practitioner watches for a colour change in the skin, described in the literature as frosting, which signals how deep the acid has acted. Reading that endpoint correctly, and neutralising at the right moment, is the difference between a controlled result and an overtreatment. This is not something a protocol on a page can substitute for, and it is the strongest argument for choosing an experienced operator for anything beyond superficial depth.
Deep peels
Deep peels reach the mid-dermis, historically using phenol-based solutions. They can produce dramatic improvement in deep wrinkling and significant photodamage, with results that can last for years. They also carry the highest risk of any peel: prolonged recovery, permanent lightening of the treated skin, scarring, and, with phenol specifically, potential cardiac effects that require monitoring during the procedure.
Deep peels are performed far less often than they once were, partly because ablative laser resurfacing now covers much of the same ground with arguably more control. A patient offered a deep peel should understand it as a procedure closer in seriousness to surgery than to a facial, requiring appropriate medical oversight.
The permanence of a deep peel cuts both ways. The results genuinely can last years, which is part of the appeal, but the permanent lightening of the treated skin means the result has to blend with untreated areas, and a full-face approach is often needed to avoid an obvious demarcation line. This is skilled, high-stakes work, and it is one of the few aesthetic procedures where the seriousness of the downside justifies genuine caution about who performs it and where.
| Class | Typical agents | Reaches | Downtime |
|---|---|---|---|
| Superficial | Glycolic, lactic, salicylic, low TCA | Epidermis | 1, 3 days |
| Medium | Higher-concentration TCA | Upper dermis | 5, 10 days |
| Deep | Phenol | Mid dermis | 2, 3 weeks plus |
Fitzpatrick type and pigment risk
The Fitzpatrick scale classifies skin by how it responds to sun, from type I (always burns, never tans) to type VI (deeply pigmented, never burns). It is central to peel safety because the deeper the peel and the darker the skin, the greater the risk of post-inflammatory hyperpigmentation and, at the deep end, permanent hypopigmentation.
For higher Fitzpatrick types this does not rule out peels. It shifts the safe zone. Superficial peels, careful priming of the skin beforehand, and conservative choices are the sensible approach, and aggressive deep peeling in darker skin is generally avoided. This is one of the clearest examples in aesthetics of why a practitioner's judgement about who not to treat matters as much as their technique. General advice from the British Association of Dermatologists on pigmentation and sun protection is directly relevant here.
Downtime, cost and choosing
The single most useful question a patient can ask is not which acid, but what depth and what recovery. A clinic that answers precisely, with a realistic account of how the skin will look during the peeling phase, is demonstrating the right kind of caution.
UK pricing in 2026 runs from roughly £90 to £200 for a superficial peel, £250 to £600 for a medium-depth peel, and considerably more for a deep peel performed with appropriate oversight. Our wider guide to what aesthetic treatments cost in the UK in 2026 sets these in context. Where a peel is deep enough to count as a medical procedure, the setting and the practitioner's registration matter, a point covered in our explainer on what an aesthetic clinic actually means in UK law.
Timing is worth planning too. Because peeled skin is vulnerable to sun, the sensible window for a medium or deep peel is autumn or winter, when exposure is easier to avoid during the vulnerable healing weeks. Booking an aggressive peel immediately before a summer holiday is a common and avoidable mistake.
Finally, sun protection is not optional aftercare, it is part of the treatment. Freshly peeled skin is vulnerable to pigmentation if exposed, and the result of a well-judged peel can be undone by a fortnight of unprotected sun. Daily broad-spectrum sunscreen, reapplied properly, is the single cheapest thing a patient can do to protect an investment in any resurfacing treatment.