Chemical Peels: Types, Depth, and Risks

A chemical peel is the controlled application of an acid solution to the skin, causing precisely measured damage to the surface layers. This triggers a regenerative process: the exfoliation of dead skin cells is accelerated, fibroblasts are activated, and collagen and elastin synthesis is enhanced. As a result, the skin becomes smoother, its texture is evened out, and the appearance of age spots and fine wrinkles is reduced. Unlike scrubs, peeling works not through mechanical friction, but by chemically dissolving the bonds between epidermal cells. [1]

The depth of action depends on the composition and concentration of the solution, exposure time, and skin preparation. In professional dermatology, peels are classified as superficial, medium, and deep, depending on whether the damage reaches only the epidermis, the upper dermis, or deeper layers. The deeper the peel, the more pronounced the effect, but the higher the risk of complications and the longer the recovery time. [2]

Chemical peels are used for more than just "radiant skin." They are used to treat the effects of photoaging, acne and post-acne scars, melasma, actinic keratosis, and several other dermatological conditions. In some cases, peels are considered as part of a comprehensive treatment plan, along with topical treatments, systemic medications, and laser procedures. [3]

The mechanism of action of different acids differs slightly. Alpha hydroxy acids primarily weaken the bonds between keratinocytes and improve exfoliation, beta hydroxy acids dissolve sebum and penetrate deeper into pores, and trichloroacetic acid causes protein coagulation and deeper dermal remodeling. However, for the patient, this is always a controlled chemical burn, meaning the procedure requires precise calculations and adherence to technique. [4]

It's important to understand that a chemical peel is a medical or paramedical procedure, not simply a "cosmetic mask." Superficial peels in salons can be performed by a trained cosmetologist under the supervision of a physician, but medium and deep peels are the responsibility of a dermatologist or plastic surgeon. This is emphasized in modern reviews and consensus statements on chemical peels. [5]

Table 1. Main objectives of chemical peeling

Task	What changes are possible?
Refresh dull skin	More even tone, slight "radiance"
Reduce fine wrinkles	Partial smoothing, smoother relief
Correct post-acne	Softening the edges of scars, leveling the surface
Lighten age spots	Reducing the appearance of melasma and post-inflammatory spots
Treat acne	Reduction in the number of comedones and inflammatory elements

Main types of chemical peels

Peels are divided into three groups based on their depth of action. Superficial peels work within the epidermis, reaching the basal layer. They provide a gentle effect and a short recovery period. Medium peels reach the papillary dermis and allow for the correction of more severe photoaging, post-acne scars, and actinic keratosis. Deep peels reach the reticular dermis and are used for severe skin damage, but are associated with high risks and are performed only in conditions similar to an operating room. [6]

Based on their composition, there are several groups of preparations. Alpha hydroxy acids (glycolic, lactic, mandelic, and others) are more often used for superficial peels and can be used in courses. Beta hydroxy acids, primarily salicylic acid, are effective for acne and seborrheic skin. Trichloroacetic acid is often the basis for medium-depth peels. Phenolic compounds are used for deep procedures and require cardiac monitoring and very strict patient selection due to phenol's cardiotoxicity. [7]

Combination solutions also exist, such as Jessner's solution, which combines salicylic acid, lactic acid, and resorcinol in an alcohol base. These mixtures are often used as a standalone superficial peel or as a first step before trichloroacetic acid for more uniform penetration. Combination protocols allow for a lower concentration of each component and a reduced risk of complications while maintaining effectiveness. [8]

The choice of peel depth and composition depends on the skin phototype, the severity of the problem, the presence of concomitant diseases, and the patient's readiness for the recovery period. For example, for melasma and post-inflammatory hyperpigmentation in patients with dark skin, gentle superficial courses are more often chosen than aggressive single medium-depth procedures. For pronounced perioral wrinkles or severe manifestations of photoaging, medium-depth and deep peels may be considered, sometimes in combination with surgical techniques.

For patients, the practical conclusion is: "the deeper, the more aggressive." Superficial peels typically require a course of several treatments, but provide gentle rejuvenation and minimal downtime. Medium and deep peels are often performed one-time or at longer intervals, producing a more noticeable effect, but require long-term care and place greater strain on the skin and body. [9]

Table 2. Classification of chemical peels

Criterion	Option	Examples of acids	Peculiarities
By depth	Surface	Glycolic, lactic, salicylic	Short rehabilitation
By depth	Median	Trichloroacetic acid of moderate concentration, combined solutions	Pronounced effect, 7-10 days of care
By depth	Deep	Phenolic compounds	High risk, long recovery
By composition	Alpha hydroxy acids	Glycolic, lactic, almond	Lightening, relief leveling
By composition	Beta hydroxy acids	Salicylic	Acne, oily skin

Indications, contraindications and patient choice

Chemical peels are used for superficial wrinkles, signs of photoaging, melasma and other pigmentation disorders, post-acne scars, some forms of acne, and actinic keratoses. With the right depth of treatment and care, you can achieve a noticeable evenness of tone and texture, a reduction in the number of age spots, and a smoothing of scars. However, peels are rarely the only treatment method; they are often combined with topical therapy and sunscreen. [10]

An important aspect of planning is assessing the Fitzpatrick phototype and the degree of photoaging using various scales. Patients with fair skin have a relatively lower risk of post-treatment hyperpigmentation than those with a darker phototype. For dark skin and a fresh tan, current recommendations recommend gentle regimens, preliminary preparation, and particularly strict photoprotection. Alternative methods should be considered if the risk of complications is high. [11]

Absolute contraindications to most peels include active bacterial, viral, or fungal infections on the face, severe dermatitis, open wounds, a tendency toward keloid scarring, severe wound healing disorders, uncontrolled diabetes, severe immunodeficiency, and unrealistic patient expectations. Pregnancy and lactation are considered contraindications for medium and deep peels, and superficial procedures during this period are assessed individually. [12]

Important limitations include recent use of systemic retinoids, particularly isotretinoin. Recent reviews indicate that deep and medium peels require a long interval after completion of therapy, while for superficial procedures, the issue is decided on an individual basis, taking into account the dose and duration of the course. Peels should also be used with caution in people with active psoriasis, atopic dermatitis, and systemic connective tissue diseases. [13]

Patient selection for deep phenol peels is particularly strict. Phenol has been reported to be cardiotoxic, with risks of arrhythmia and toxic effects on the liver and kidneys. Therefore, such procedures require cardiac monitoring, intravenous hydration, and the exclusion of patients with severe cardiac, hepatic, or renal disease. In modern practice, deep phenol peels are performed much less frequently and only in specialized centers.

Table 3. Who is suitable for chemical peeling and who is not

Situation	Peeling is usually acceptable.	Peeling is not recommended
Photoaging, fine wrinkles	Superficial and medium peels	Deep ones - only for strict indications
Acne and post-acne	Superficial peels, especially with salicylic acid	For active skin infection
Melasma and pigmentation	Gentle surface courses with preparation	If it is not possible to observe photoprotection
Tendency to keloids	Only very superficial protocols or refusal	Medium and deep peels
Pregnancy and lactation	The issue is decided individually; it is preferable to avoid aggressive procedures.	Medium and deep peels

Preparing skin for chemical peeling

The preparatory stage begins with a detailed medical history and skin examination. The doctor will determine the duration and severity of the problem, previous treatments, tolerance to cosmetics, and the presence of herpes, acne, rosacea, allergies, and systemic diseases. Particular attention is paid to medications, including retinoids, immunosuppressants, anticoagulants, and photosensitizing drugs. If necessary, treatment adjustments are discussed with other specialists.

Many protocols include "pre-peel" skin preparation. Several weeks before the procedure, the patient begins using gentle preparations containing alpha hydroxy acids or retinoids as prescribed by the doctor, unless contraindicated. This helps smooth the stratum corneum, improve the penetration of the main solution, and accelerate healing. At the same time, sun exposure is strictly limited, and a high-factor sunscreen is prescribed.

For melasma and severe pigmentation, lightening agents based on hydroquinone or alternative ingredients are often additionally prescribed. They are used before and after peels to reduce the risk of post-inflammatory hyperpigmentation and improve the final result. It is important to strictly follow your doctor's recommendations regarding the duration of treatment and application schedule, as some bleaching agents require limited use.

Patients with recurrent herpes on the lips or face are almost always prescribed a prophylactic course of antiviral medications before medium and deep peels. This significantly reduces the risk of painful breakouts during the healing stage, when the skin's barrier function is weakened. In some cases, a short course of antibiotics is also considered if there is an increased risk of bacterial complications.

Cosmetic and lifestyle restrictions prior to the procedure include avoiding aggressive peels, scrubs, waxing, and threading for several days, limiting alcohol and smoking, and choosing gentle cleansing and moisturizing products. During the consultation, the expected sensations during and after the peel, the recovery period, and the need for temporary abstinence from tanning beds and the beach are discussed in detail. Informed consent is required. [14]

Table 4. Basic elements of preparation for peeling

Preparation step	Why is this necessary?
History taking and examination	Evaluation of indications, risks and contraindications
Medication adjustments	Reduced risk of poor healing and complications
Use of acids and retinoids according to the scheme	Smoothing of the stratum corneum, better penetration
Lightening therapy for pigmentation	Prevention of hyperpigmentation
Herpes prevention	Preventing painful breakouts

How is a chemical peel performed by a doctor?

On the day of the procedure, the skin is cleansed of makeup and impurities, and if necessary, additional degreasing is performed with special solutions. Eyes are protected with special shields or intraocular lenses, and hair and clothing are covered. Depending on the depth of the peel, local anesthesia is applied in the form of a cream, cooling, or, for more serious procedures, sedation under medical supervision.

The solution is applied to specific areas of the face using cotton applicators, brushes, or sponge applicators. The doctor evaluates the skin's reaction based on the color and degree of redness, as well as the appearance of the characteristic "frost" caused by the trichloroacetic acid. For superficial peels, the exposure time is minutes, while for medium and deep peels, the procedure is more thorough, with the depth of action monitored based on clinical signs. The contact time and number of layers are strictly regulated.

With superficial peels, after achieving the desired effect, the solution is neutralized with water or special compounds, followed by the application of soothing and moisturizing agents. Medium protocols are more aggressive, causing significant redness and swelling, followed by crusting. Deep phenol peels are performed in stages, treating individual areas of the face at intervals, with infusion therapy and cardiac monitoring.

An important part of the procedure is patient safety and comfort. Fans and cooling, soothing compresses, and mild painkillers are used. The doctor explains in advance which sensations are considered normal and which require immediate attention: sharp pain, a strong burning sensation, or an unusual reaction in one area. This feedback helps promptly adjust parameters and reduce the risk of complications. [15]

After the procedure, the skin is covered with protective agents. The patient receives detailed verbal and written aftercare instructions, a list of permitted and prohibited products, information about follow-up appointments, and signs that require an unscheduled visit. For medium and deep peels, several follow-up visits are scheduled to assess healing and detect complications early. [16]

Table 5. Stages of professional chemical peeling

Stage	Content
Preparation on the day of the procedure	Cleansing, degreasing, eye and hair protection
Anesthesia	Cream, cooling, or medicinal sedation
Application of the solution	Time and clinical signs of depth control
Neutralization	Rinsing or special neutralizing compounds
Application of protective agents	Soothing ointments and gels
Briefing	Care recommendations and follow-up visit schedule

Recovery and care after chemical peeling

After a superficial peel, mild redness, a feeling of tightness, and minor peeling, reminiscent of a sunburn, are typically observed. These symptoms last from one to several days, after which the skin appears fresher and smoother. With repeated use of superficial treatments, the effect accumulates and becomes more noticeable. [17]

Medium peels are accompanied by more pronounced swelling, redness, crusting, and flaking. Complete epithelialization usually takes about 7-10 days, while residual erythema may persist longer. During this period, it is extremely important to carefully follow the aftercare instructions, avoid removing crusts yourself, and avoid using makeup until cleared by your doctor.

Deep phenol peels offer the longest recovery period. Crusting and severe redness may persist for weeks, while persistent erythema can last for months. Patients should be prepared for temporary restrictions in social and professional activities. Therefore, such procedures are performed only for serious indications, and the patient's psychological readiness is discussed in advance. [18]

Basic skincare during the recovery period includes using gentle cleansers without harsh surfactants, regularly applying healing and moisturizing creams, and avoiding scrubs and harsh sponges. Strict sun protection is essential from the first few days and continues for months: daily use of high-factor sunscreen, renewing the layer throughout the day, and physical protection with hats and sunglasses. [19]

A doctor may additionally recommend lightening agents, courses of low-concentration acids, or other procedures to maintain the results, but only after the skin's barrier function has been fully restored. Signs of complications, such as blisters, purulent discharge, severe pain, severe itching, or uneven darkening of areas, require immediate attention rather than self-medication. [20]

Table 6. Approximate recovery times depending on the depth of peeling

Type of peeling	Epithelialization	Erythema	Overall period of visible recovery
Surface	1-3 days	Up to 3-5 days	About 1 week
Median	7-10 days	Up to several weeks	2-4 weeks
Deep phenolic	More than 10 days	Up to several months	Up to six months and longer

Possible complications and safety of the procedure

Even when performed correctly, chemical peels can cause side effects. Expected side effects include redness, swelling, a burning sensation, dryness, peeling, and temporary increased skin sensitivity. These side effects usually resolve without consequences if aftercare instructions are followed. They are clearly described in the procedure manuals and are considered part of the normal healing process. [21]

More serious complications include post-inflammatory hyperpigmentation, hypopigmentation, persistent erythema, worsening acne or rosacea, milia formation, and bacterial and herpes infections. The likelihood of such problems increases in patients with a darker skin type, with improper skin care regimens and schedules, failure to adhere to sun protection, or the use of aggressive products during the recovery phase. [22]

The most serious complications include scarring, severe pigmentation changes, and the toxic effects of phenol during deep peels. Research shows that the risk of such complications is closely related to the physician's experience and adherence to the procedure. With phenol peels, cardiotoxicity and stress on the liver and kidneys are also considered, so heart rate monitoring and proper infusion therapy are essential. [23]

Key measures to prevent complications include proper patient selection, adequate skin preparation, careful procedure execution, strict photoprotection, and regular follow-up examinations. Recent consensus guidelines on chemical peels emphasize the importance of standardized protocols, specialist training, and patient education about the real risks, not just the benefits. [24]

It's helpful for patients to be aware of the "red flags" that require immediate medical attention: a sharp increase in pain, the appearance of blisters with cloudy fluid, clearly defined dark brown or whitish areas, severe swelling of the eyelids and difficulty opening the eyes, and a significant deterioration in well-being. Timely intervention can often stop complications at an early stage. [25]

Table 7. Common complications of chemical peeling

Complication	How does it manifest itself?	What do they usually do?
Post-inflammatory hyperpigmentation	Darkening of treated areas	Lightening agents, strict photoprotection
Hypopigmentation	Areas of lighter skin	Long-term observation, sometimes camouflage
Infection	Pain, pus, crusts with an unpleasant odor	Urgent medical attention, local or systemic therapy
Scarring	Compacted areas, unevenness	Treatment by a dermatologist, sometimes hardware methods
Long-lasting erythema	Redness lasts longer than expected	Gentle care, vascular procedures if necessary

Chemical peeling at home: limits of permissibility

Interest in at-home acid treatments has skyrocketed, with a plethora of products marketed as "at-home peels." These can be safe when chosen and used correctly, but are not equivalent to professional medium- and deep-cleansing treatments. At-home peels should contain low concentrations of alpha and beta hydroxy acids and follow manufacturer-provided directions for use. [26]

Dermatologists warn that highly concentrated solutions of glycolic, salicylic, lactic, and especially trichloroacetic acid are not intended for home use. In a number of countries, regulators and professional societies are raising concerns about the risk of severe chemical burns, scarring, and long-term pigmentation changes associated with home use of such compounds, especially those purchased online without quality control. [27]

Homemade acid-based treatments should be introduced gradually: start with low frequency of use, test on a small patch of skin, and combine with good moisturizing and sun protection. It's not recommended to use multiple aggressive active ingredients simultaneously, such as acid peels with retinoids and benzoyl peroxide, to avoid overloading the skin and damaging the barrier. [28]

It's important to realistically assess your goals. If you're looking for a light evening of tone and texture, low-acid products can be useful for home care, provided they're used judiciously. However, if you're dealing with severe wrinkles, deep scars, or complex pigmentation issues, attempting to "do a professional peel at home" is dangerous and more likely to lead to complications than savings. In such cases, it's best to discuss the issue with a dermatologist. [29]

Finally, with any acid skincare regimen, the key principle remains the same: the more intense the exfoliation, the more rigorous the sun protection. Even with gentle home remedies, the skin becomes more sensitive to UV rays, and ignoring sunscreen negates the benefits and increases the risk of pigmentation. [30]

Table 8. Chemical peeling at home: what is acceptable and what is not

Action	Safety assessment
Products with low acid concentrations according to the instructions	Acceptable with careful approach
Buying professional trichloroacetic acid solutions for home use	Dangerous, high risk of burns
A simultaneous combination of acids, retinoids and rough scrubs	High risk of barrier damage
Ignoring sunscreen	Significantly increases the risk of pigmentation
Trying to do a medium or deep peel yourself	This is unacceptable; a doctor's work is needed.