Chemical peels are used to create an injury of a defined skin depth with the aim to stimulate collagen and epidermal regeneration, enhancing the texture and appearance of the skin whilst creating a more evenly distributed melanin

The benefits of chemical peels are numerous with the prime goal to enhance the clinical appearance of the skin. They serve to address inflammatory and non-inflammatory acne lesions as well as acne scarring. They also manage pigmentary disorders such as photoageing and inflammatory dermatoses. In addition, they restore skin moisture, stimulate collagen and elastin, and reduce the quantity and quality of fine lines and wrinkles. In essence, they play an integral role in the overall skin rejuvenation and youthful appearance.

Table 1: The benefits of chemical peels in aesthetics and dermatology

Acne	Scars	Post acne pigmentation	Acne Vulgaris	Comedonal acne	Acne excoriée
Pigmentation	Facial melanoses	Post-inflammatory hyperpigmentation	Lentigines	Freckles	Melasma
Aesthetic	Fine lines and wrinkles	Photoageing	Dilated pores	Superficial scars
Epidermal	Actinic Keratoses	Seborrheic Keratoses	Sebaceous hyperplasia	Milia	Warts

The term peeling originates from the English word to peel = to come off in sheets or scales, to shed the outer layer, or to strip off.

This process involves the application of a chemical agent to the skin leading to the controlled destruction of part or all of the epidermis through chemoexfoliation which is then followed, by an organized regeneration of the skin.

A brief history of chemical peels

Chemexfoliation, has been used for centuries to improve signs of ultraviolet light-induced sun damage.

In fact, chemical peels have been used since ancient times and were first described in Egyptian medicine in 1150 BC. In ancient Egypt, Cleopatra used sour milk, which is now known to contain lactic acid. This practice was also described in ancient Greek and Roman literature.

In 1874, Ferdinand Von Hebra, a dermatologist from Vienna applied chemical peels for the treatment of melasma, whilst in 1882, in Hamburg, Paul G. Unna demonstrated the properties of salicylic acid, resorcinol, trichloroacetic acid (TCA) and phenol on the skin. The use of phenol was developed in France after the First World War.

In the 1940s, Eller and Wolff from the United States provided the first systematic description of the use of phenol, salicylic acid, resorcinol, and dry ice for the treatment of scars. Whilst in England, Mac Kee applied the use of phenol to treat scars but did not publish his results until 1952.

Common peeling agents in aesthetic and clinical practice

Chemical peels are routinely applied in everyday practice to manage and maintain skin health and address skin disease. Commonly used acids include,

Alpha hydroxyl acids (AHA) such as lactic, glycolic, and mandelic to name a few. These acids provide humectant benefits, reduction in hyperkeratinization, inhibition of melanogenesis, and promote collagen synthesis in the skin. Mandelic acid has the added benefit of antibacterial properties and is therefore useful for acne-prone skin.

Beta hydroxyl acids (BHAs) such as salicylic acid (SA), is an aromatic carboxylic acid that is lipophilic keratolytic in nature with the ability to dissolve follicular impactions thereby reducing acne lesions. Its benefits are attributed to its effective anti-inflammatory and exfoliating properties.

A derivative of SA, β-lipo hydroxy acid (LHA, up to 10%) provides chemoexfoliation at lower concentrations with the added benefit of anti-inflammatory, antifungal, and anticomedonic properties. LHA has an additional fatty acid chain which makes it more lipophilic than SA with regards to its mode of action and keratolytic effect. Therefore, penetrates with ease into the sebaceous follicle but less deeply into the skin than glycolic or salicylic acid. In essence, it targets the follicle and the epidermis with a PH of 5.5, similar to normal skin, therefore, a more tolerable experience for the patient. Similar to SA, it is also self-neutralizing.

Pyruvic acid is an alpha-keto acid that delivers superficial exfoliating action similar to salicylic acid, with a lesser degree of lipophilicity. However, it is also partially hydrophilic therefore exhibiting features similar to glycolic acid. It is commonly applied as a superficial peeling agent for the treatment of inflammatory and comedonal acne but is not as effective as salicylic acid. It is used in the treatment of acne vulgaris and associated disorders of excess sebum production due to greater lipophilic properties and ease of penetration through the lipid barrier. It is also used in the management of mild photoaging and superficial hyperpigmentation. Although pyruvic acid displays similar properties to salicylic acid, it is not self-neutralizing and is similar to glycolic acid, where neutralization is required.

TCA is a caustic peeling agent that coagulates skin proteins. Observation during the treatment is vital when assessing the end point of action. The PH and the depth of penetration are concentration-dependent. Therefore, becomes more acidic and penetrates deeper with increasing concentration. TCA is a versatile peeling agent commonly applied to improve fine lines, wrinkles, smooths skin texture, and acne scarring as well as in the treatment of actinic keratosis and melasma.

Retinol is one of the most popular peels in my practice. Retinol is converted to retinoic acid in the skin to encourage cellular turnover and normal skin shedding to reveal brighter glowing skin. Retinoids suppress melanin production, stimulate the production of collagen and discourage hyperkeratinization within the follicle. They also increase water content in the epidermis. Their overall advantage of being safe for all skin tones.

Phenol is also known as carbolic acid or hydroxybenzene (C6H5OH) derived from coal tar. It is a hydrophobic, aromatic alcohol, with cytotoxic, antiseptic, and analgesic properties. It functions as a protoplasmic poison by altering cell membranes, deactivating enzymes, and producing insoluble proteinates.

Resorcinol is a caustic agent from the phenols group, with different properties. It serves as an exfoliant and is applied in the form of solutions or ointments, with concentrations ranging from 10-70%, it is also incorporated with other chemical peel preparations.

The modified Jessner’s solution was the first documented blended acid peel with chemoexfoliating and keratolytic properties used for the treatment of acne, dyschromia, and extrinsic aging. The modified Jessner’s solution is often administered due to its ease of use, lower risks, and uniform depth with the advantage of being suitable for most skin tones.

Other peeling agents include arbutin, L-ascorbic acid (vitamin C), azelaic acid, citric, tranexamic acid, glutathione, Kojic acid, lactic acid, and phytic acid where some have antioxidant properties and serve to suppress melanin production whilst promoting evenly distributed skin tone.

Classification of chemical peels

Chemical peels are classified by the depth of penetration and mode of action as well as the treatment objective. Applying the appropriate depth determines the overall success of the treatment whilst minimizing the risk of complications.

Very superficial peels function to remove the stratum corneum at a depth of 0.06 mm, superficial peels induce epidermal exfoliation of the granular layer to the basal layer at a depth of 0.45 mm, medium depth peels target the papillary dermis at a depth of 0.6 mm and deep peels penetrate the mid reticular dermis at a depth of 0.8 mm.

Figure 1: Visual representation of the intended depth of chemoexfoliation demonstrating the depth of penetration. Superficial peels penetrate the epidermal layers; medium-depth peels cover the entire epidermis and a portion of the papillary dermis; deep peels penetrate the mid-reticular dermis.

Clinical Applications

Superficial peels are beneficial in the treatment of mild discoloration and patchy skin, acne, and post-inflammatory pigmentation. rejuvenating effects are predicted between three to five days.

They exert their beneficial effecs mode through exfoliation and an increase in dermal collagen to achieve radiant, luminous and rejuvenated skin.

Medium-depth peels on the other hand are indicated in the treatment of dyschromia, such as solar lentigines, multiple keratoses, superficial scars, pigmentary disorders, and textural changes. The treatment involves a longer healing process where full epithelialization is achieved in seven days.

Deep peels are used to address photoaging, deep or coarse wrinkles, scars, and in some cases precancerous skin lesions. Deep peels lead to the denaturation of surface keratin and other proteins in the dermal and epidermal layers of the skin making their journey to the reticular dermis with the objective to potentiate collagen regeneration. Epithelialization resumes within five to ten days where a significant healing time of two months or more may be required.

Superficial peels are generally considered safe in the skin of colour whilst caution must be applied when considering medium-depth peels. It is strongly advised that deep peels are not performed on the skin of colour.

However, it is always important to assess skin of colour through an in-depth consultation as what may be superficial can behave as medium depth and therefore patient selection and assessment are paramount.

Peel intensity

There are a number of contributing factors to peel intensity. These include the status of the skin at the time of the treatment, for example, is the skin prepped? It may be essential to prep or prime the skin especially the skin of colour prior to treatment, with the use of ingredients such as hydroquinone, retinoid, vitamin C, and sunscreen. Peel intensity may also be influenced by the amount of peel applied, the number of layers, the concentration used, the time left on the skin, and the location and thickness of the area treated, for example, the face or body.

Table 2 Classification of chemical peeling agents based on concentration and depth of tissue injury.

TYPE		DEPTH OF PENETRATION	POTENTIAL SIDE EFFECTS
Superficial	· • AHAs such as glycolic (30–50%), lactic (10–30% or mandelic (40%) · • BHAs such as salicylic acid (30%) · • AKAs such as pyruvic acid (50%)	Intraepidermal and DE junction disruption possible	Post-inflammatory pigmentary alterations, erythema, pruritus, burning, superficial desquamation/epidermolysis
Medium	· • Salicylic acid (>30%, multilayer application) · • Glycolic acid (70%, with or without pretreatment primer such as Jessner’s solution) · • TCA (30–50%, monolayer application, with or without pretreatment primer such as Jessner’s solution)	Full thickness epidermis into the papillary dermis	Post-inflammatory pigmentary alterations, superficial bacterial or fungal infection, reactivation of HSV, scarring, milia, acneiform eruption, greater thickness desquamation/epidermolysis
Deep	· • TCA (>50%,	Full thickness epidermis, papillary dermis, and mid-reticular dermis	Post-inflammatory pigmentary alterations, secondary bacterial or fungal infection, reactivation of HSV, scarring, milia, acneiform eruption, cardiotoxicity/arrhythmia (due to systemic absorption of phenol, seen in 34–50% of patients), hepatotoxicity, nephrotoxicity

The importance of priming the skin prior to a chemical peel

Priming or prepping the skin prior to performing a chemical peel can yield a number of benefits such as creating an even and better distribution of the peel at the time of treatment, reducing the risk factors such as hyperpigmentation, reduces the wound healing time, thereby aiding skin recovery. It also creates positive skincare maintenance habits.

Combination treatments with rejuvenating agents have shown to deliver impressive results for various skin concerns such as photoaging.

Considerations with chemical peels:

Detailed knowledge of skin anatomy and the mechanism of the wound healing process is vital for safely treating the skin.

An in-depth consultation and patient assessment with detailed medical and patient history are paramount prior to a chemical peel treatment to assess suitability whilst adhering to the exclusion criteria.

The consultation also serves to explore the patient’s ideas and concerns including evaluation of psychological aspects to determine the motivation and goal emphasizing realistic expectations, particularly in social media-focused patients. A clear description of the treatment should be covered during the consultation which includes the treatment procedure, undesirable side effects, recovery time as well as aftercare instructions. The patient must be provided with information regarding the risks as well as the benefits of the treatment to establish informed consent.

Contraindications to chemical peels include

History of allergic reaction to the peeling agent, or any known past or present allergies
Active skin infections such as viral, fungal, and bacterial
Open wounds
Skin conditions with pre-existing inflammatory dermatosis such as psoriasis, atopic dermatitis
Non-adherent patient with regards to aftercare instructions
Medication with photosensitising properties. The use of isotretinoin within six months previous to the attended chemical peel treatment.
Unmet and unrealistic patient expectations

It is important to consider patients with abnormal scarring and Keloids, atrophic skin, patients with immunosuppression, uncontrolled diabetes, as well as patients with Fitzpatrick III-VI as they may be prone to pigmentation or dyschromatopsia.

Complications of Chemical Peels

There are a number of factors that may determine the risk of a complication. This includes

Product selection
The procedure was performed.
The depth of the peel in relation to the skin concern or skin colour
Inappropriate patient selection
The skill of the practitioner.

Such complications include pigmentary changes, post-inflammatory, hyperpigmentation or more persistent and very difficult to treat hypopigmentation (loss of colour), bacterial infections such as Staphylococcus, Streptococcus, Pseudomonas), viral (herpes simplex), fungal skin infections, allergic reactions, milia, acneiform eruptions, demarcation lines, and scar formation. Product and patient selection and robust adherence to aftercare instructions including the use of sunscreen can minimize the risk of complications.

The rise in popularity of blended peels

Blended or combination peels have gained an increase in popularity due to their ease of application, decreased risks, and increased recovery enabling a wider demographic of patients to be treated. Combination peels can yield a higher and earlier therapeutic response with a cost-effective approach that enables ongoing maintenance leading to greater patient satisfaction.

Combination peels are not a new concept as the Jessner’s Peel was developed by Max Jessner, MD, in 1860. The appeal of Jessner’s Peel was the use of different substances that combined caustic, metabolic, and toxic effects.

So, what is the deal with a blended peel?

Blended peels are a collection of acids at lower concentrations and advanced formulations with medium-depth penetration. Blended peels are more controlled in their penetration than straight acid peels. They are formulated at lower percentage concentrations, enhanced delivery systems, melanogenesis inhibitors, antioxidant ingredients, and hydrating and rejuvenating agents making them an all-inclusive peel for all skin tones. Their formulations enable them to create and deliver clinical outcomes with a lower risk of inflammation or complications.

There are a number of blended peels on the market. These include the VI peel, The Perfect Peel, the BioRePeel Cl3, and PRXT33 to name a few.

The VI Peel portfolio, for example, is made of medical-grade peels which penetrate the papillary dermis resulting in specific regenerative changes. All VI Peels preparations are self- neutralizing with light to the medium depth of penetration depending on the application technique.

I love this peel as it is safe for all skin tones

The peel is formulated for all skin tones to address skin concerns with a percentage of acids of <15%. They also do not require pre-treatment of the skin. However patient assessment is advisable.

An efffective peel for all skin tones

All VI Peels are formulated using synergistic blends of TCA, phenol, retinoic acid, and salicylic acid at lower individual concentrations. This combination allows the VI Peel to penetrate the dermis without the destruction or longer healing time that a straight acid would incur yet, achieving the desired outcome. The blended VI Peel formulations have added nutrients such as antioxidant vitamin C, in addition to ingredients for pigment suppression and acne control, allowing the peels to address conditions that stand alone may not be suitable.

Once the treatment is completed, the patient is armed with an aftercare kit to ensure successful and safe completion of the treatment.

The Perfect Peel adopts a similar approach to the VI peel where an aftercare kit is also provided. However, their hero ingredient is Glutathione. According to the manufacturers, combining glutathione into a medium-depth peel is an effective mechanism for allowing it to penetrate at depths to induce its antiageing and skin harmonizing properties

The BioRePeelCl3 on the other hand adopts a different mechanism of action and formulation. The BioRepeel is a biphasic peel. The hydrophilic phase consists of 35% trichloroacetic acid, salicylic acid, tartaric acid, citric acid, and lactobionic acid. It is also formulated with ascorbyl glucoside, riboflavin, and amino acids: arginine, glycine, proline, and hydroxyproline. In addition to gamma-aminobutyric acid (GABA). The lipophilic phase includes a natural moisturizer squalane and isopropyl myristate that functions as a delivery vehicle. Although BioRepeel is formulated with a high percentage of TCA (50% for the body formulation) the side effects are minimal. This is due to the formation of trichloroacetate salt maintaining the action of TCA whilst minimizing adverse effects.

The penetration of the product is also facilitated by isopropyl myristate, which serves as a vehicle due to its hydrophilic and lipophilic portion improving the permeability into the skin. The Biostimulating complex increases cellular turnover, and dermal fibroblast, thereby, leading to the production of collagen, especially type III and I.

This powerful peel is one of the most versatile peels in my practice as I can also combine microneedle with this peel in the same session to supercharge collagen induction and it is suitable for all skin types

The multifunctional peel like no other

PRXT33 is a biorevilalisation peel, with a similar method of application to the BioRepeel. However, PRX-T33 combines 33% trichloroacetic acid with hydrogen peroxide to produce what the manufacturers term a new type of peel. The mechanism of the action of oxygenated water combined with the TCA minimizes the aggressive effects of peeling (frost or exfoliation of the dermis), stimulating the dermis non-invasively.

The advantage of blended peels is that they can create an exfoliating effect whilst rejuvenating the skin. The added nourishing ingredients eliminate the need for acid neutralization which is not possible with single-use peels. Utilizing multiple acids that are blended together at lower percentages enhances clinical outcomes and reduces the risk of undesirable effects. In addition, their formulations lend themselves favourably to combination therapies and some may be performed in the same appointment session. A multimodality approach can address a multitude of skin concerns thereby, increasing patient satisfaction. However, it is worth noting that prior to adopting a multimodality approach, confidence in successfully treating the patient with a standalone blended peel should be accomplished.

Conclusion:

Chemical peels are a staple part of the cosmetic practitioner’s toolbox, they are popular, relatively inexpensive, and generally, a safe method in the right professional hands to treat a multitude of skin disorders with rejuvenating and skin-refreshing benefits. In addition, combining chemical peels with other resurfacing and rejuvenation procedures can provide a synergistic approach with favourable outcomes tailored, to the patient individual skin goals.

It is vital that chemical peel treatments are performed by trained professionals with an in-depth knowledge of skin anatomy as their purpose is to induce controlled trauma and therefore, with untrained and inexperienced hands, chemical peels may lead to skin damage.

Consideration of potential complications and contraindications is paramount prior to commencing the treatment. Patient selection and in-depth consultation with a detailed medical history and appropriate skin priming are vital for a predictable and safe outcome. Checking the patient’s understanding with regards to the importance of aftercare instructions and a skincare regimen including the daily use of broad-spectrum sun protection plays an integral role in the treatment outcome.

The versatility, safety, controlled and predicted outcomes of blended peels position them favourably in an ever-glowing aesthetic industry where patient expectations and time constraints are factors. The blend of ingredients that are formulated with unique delivery systems and ease of use, creates a powerful tool for skin transformation thereby increasing patient satisfaction and retention. Their formulations enable combination therapies to be performed in the same treatment session freeing time for both practitioner and the patient.

Achieving healthy, beautiful skin for patients is the ultimate goal of all aesthetic practitioners. Skin peeling treatments add tremendous value to skin health. However, they need to be supported by an effective skincare routine. It is vital for me to educate, enable and empower all my patients to own their skin journey by providing them with a complete care solution for their skin health.

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Derm Refine