Chemical Peels for Skin Resurfacing

Anatomy and Physiology

A basic comprehension of the skin's layered structure is essential for understanding the various chemical peels and their depth of action.[4] The skin comprises 3 primary layers—the epidermis, the dermis, and the subcutaneous tissue, also referred to as the hypodermis.

Epidermis 

The epidermis is an avascular layer consisting of 4 distinct layers. Keratinocytes, which are primarily squamous cells, populate all layers except the stratum basale, where a single layer of cuboidal stem cells is present. These keratinocytes produce keratin—a crucial protein found in the skin, hair, and nails.

Stratum corneum: This is the most superficial layer that serves as a protective barrier comprising 15 to 30 layers of highly keratinized dead cells. These keratinized cells are continually shed and replaced by the underlying layers, contributing to the skin's renewal and protection.

Stratum granulosum: This layer contains squamous cells with a distinctive grainy appearance when examined under light microscopy, a characteristic result of increased keratin protein content.

Stratum spinosum: This layer comprises cells with prominent processes that interconnect through desmosomes, thereby maintaining the cohesion between squamous skin cells. Within this layer, Langerhans macrophage cells are interspersed.

Stratum basale: This layer is situated at the base of the epidermal layer and connects it to the dermis. Within this layer, melanocytes are responsible for producing melanin pigment, whereas Merkel cells are involved in sensory touch stimulation.

Stratum lucidum: This layer is located exclusively on the palms and soles of the feet and is situated deep to the stratum corneum.

Dermis 

The dermis is a connective tissue layer comprising various structures, including hair follicles, sebaceous glands, nerves, and blood vessels.

Papillary layer: This layer consists of finger-like projections known as dermal papillae, which intertwine with the stratum basale and connect the epidermal and dermal layers.

Reticular layer: This layer is situated beneath the papillary layer and is rich in elastin and collagen fibers. This layer provides the skin with its elasticity and tensile strength. The reticular dermis comprises upper, mid, and lower layers within this structural framework. 

Hypodermis

The hypodermis, also known as the subcutaneous tissue, is the deepest layer of the skin and is composed of loose connective tissue and adipose tissue.

Chemical peels are commonly classified as light, medium, and deep, depending on their depth of skin penetration. Light peels induce localized injury within the epidermis and are particularly effective for conditions such as acne and hyperpigmentation, and they also provide mild improvements in skin texture. Medium peels penetrate from the epidermis through the papillary dermis into the upper reticular dermis. These peels are suitable for addressing concerns such as hyperpigmentation, actinic keratoses, superficial acne scars, and shallow wrinkles. Deep chemical peels extend their effects into the mid-reticular dermis, rendering them valuable for addressing more profound issues such as severe acne scars and deep wrinkles.[5]

Indications

Effective execution of a comprehensive treatment plan and thorough patient evaluation during a chemical peel procedure can lead to safe, reliable, and satisfactory outcomes. Numerous indications support the use of chemical peeling as a skin resurfacing technique, which include acne vulgaris, melasma, postinflammatory pigmentation, lentigines, ephelides, enlarged pores, rhytides, rosacea, pseudofolliculitis barbae, acne scars, sebaceous keratosis, actinic keratosis, striae distensae, and deep wrinkles.[3][6][7][8][9]

Contraindications

Most precautions and contraindications primarily pertain to medium and deep chemical peels. Contraindications and precautions for all chemical peels include:[10][11]

• Active infection 
• Fitzpatrick skin types III to VI  
• Phenol-based peels in patients with renal or hepatic disease
• History of an allergic reaction to a peeling agent
• Open lacerations or wounds in the area of the peel
• Active treatment with isotretinoin
• Body dysmorphic disorder

Precautions and contraindications specific to medium and deep chemical peels include:

• Recent isotretinoin use within the past 6 months
• Pregnancy or breastfeeding
• Psoriasis
• Connective tissue diseases
• Atopic dermatitis
• Poor wound healing
• Recent facial surgery 
• Uncontrolled diabetes or immunosuppression
• Malnutrition
• Protein deficiency
• Chronic glucocorticoid use
• Smoking
• Prior exposure to radiation therapy
• A known predisposition to keloid formation

Equipment

The peeling agent is the primary and most crucial component when performing a chemical peel. The pKa represents the pH level at which 50% of the chemical is present in a free acid state. When selecting the type of peel, a lower pKa is associated with a more potent peel. Peeling agents are primarily classified into 2 categories—keratolytics and protein denaturants.[1] 

Keratolytics

Keratinolytics disrupt bonds between keratinocytes, forcing them to shed. The examples of a few keratolytic agents with their functions are listed below.

Glycolic acid: This alpha hydroxy acid (AHA) is mainly derived from fruits and is a member of the carboxylic acid family. In AHAs, the hydroxyl group is attached to the alpha position of the molecule. AHAs include glycolic acid from sugar cane, lactic acid from milk, and citric acid from citrus fruits. To cease its action during a peel, glycolic acid necessitates a neutralizing agent, such as sodium bicarbonate and water.

Salicylic acid: This beta hydroxy acid (BHA) features a hydroxyl group connected to the second carbon. Salicylic acid boasts higher lipophilicity than glycolic acid, allowing it to penetrate the skin more effectively. This lipophilic property makes salicylic acid an excellent option for acne treatment, as it can effectively permeate acne lesions and oily skin.

Jessner solution: This solution is a mixture of 14% resorcinol, 14% salicylic acid, and 14% lactic acid dissolved in ethanol. Jessner solution is primarily used for the treatment of acne and hyperkeratotic lesions.

Other keratolytic agents: Additional keratolytic formulations include 40% mandelic acid, a combination of 20% salicylic acid and 10% mandelic acid, 10% to 30% lactic acid, 40% to 70% pyruvic acid, retinoic acid, and resorcinol—a phenol derivative. 

Protein Denaturants 

Trichloroacetic acid (TCA): TCA is a widely used peeling agent, and its effects vary based on concentration, the number of applications during a session, and whether it is used in a solution. TCA primarily addresses photodamage, actinic keratoses, lentigines, fine rhytides, and superficial acne scars.

Phenol and croton oil: Phenol, a potent aromatic hydrocarbon, is often utilized in deeper peels, whereas croton oil is a vesicant and epidermolytic agent. The incorporation of croton oil enhances the depth and uniformity of the results. A blend of phenol 88%, hexachlorophene, soap, croton oil, and distilled water is combined to formulate the Baker-Gordon solution.[2] Phenol is commonly used to treat various conditions such as photodamage, rhytides, acne scars, xanthelasma, actinic keratoses, actinic cheilitis, and lip augmentation. 

The examples of common agents alongside their corresponding depth of effect are listed below.[5][12]

• Very light peels: They include agents such as 10% to 20% TCA, low-potency glycolic and salicylic acid, and retinoic acid.
• Light peels: They include agents such as 20% to 30% TCA, Jessner solution, and 30% to 50% glycolic acid.
• Medium peels: They include combinations such as 35% TCA with either Jessner solution or 70% glycolic acid.[5]
• Deep peels: They include TCA exceeding 50% and combinations of croton oil and phenol.

Although the specifics of each agent's mechanism of action are beyond the scope of this review, the fundamental principles are typically consistent. Chemical peels induce keratolysis, coagulation, and denaturation of proteins in both the dermis and epidermis skin layers. Peels that penetrate the basal layer containing melanocytes can effectively address uneven pigmentation. In contrast, those targeting the papillary or upper to the mid-reticular dermis contribute to the reduction of superficial rhytids due to the deposition of elastin and collagen.[5][12]

In the interest of patient safety, it is imperative to have resuscitation equipment readily available in a well-ventilated procedure room. Additionally, cardiac monitoring should be accessible when employing phenol, as it carries a risk of cardiotoxicity.

Other Necessary Equipment

To ensure a safe and effective chemical peeling procedure, several other essential equipment and materials are required, which include:

• Skin cleansing solutions, such as acetone or 70% alcohol
• Application tools, such as cotton-tipped swabs, gauze, or brush
• Receptacles or a small, stainless steel surgical bowl for peeling agents
• Neutralizing agents for glycolic acid peels
• Saline to flush eyes in the case of accidental exposure to non-phenol peeling agents
• Mineral oil to flush eyes in the event of phenol entry
• An electric fan or forced-air cooling unit 
• Gloves and appropriate personal protective equipment specific to the type of peel solution

Personnel

A clinician who has received training in applying and managing skin disorders necessitating chemical peeling can conduct this procedure in the presence of an assistant to provide support and assistance. If general anesthesia is administered for this procedure, an anesthesiologist must be present, and a specialized team must be on hand for cardiac monitoring, fluid administration, and advanced cardiac life support during a phenol peel procedure.[5]

Preparation

Before proceeding with this procedure, obtaining informed consent from the patient is essential. Furthermore, it is advisable to encourage photo documentation for preoperative and postoperative comparisons to maintain comprehensive medical records. Post-peel expectations should be discussed with the patient. In addition, it is imperative to conduct a complete history and physical examination of patients to rule out any contraindications for the procedure, as mentioned previously.

The initial step involves selecting the appropriate peel depth, considering the patient's skin type and the specific condition that requires treatment. A widely adopted system for classifying skin phototypes is the Fitzpatrick classification.[13] The Fitzpatrick classification system categorizes patients into 6 distinct skin types based on their reactions to sun exposure, as mentioned below.

• Type I: Individuals with white skin, blue eyes, freckles, and light hair. Their skin tends to develop sunburn with sun exposure and does not tan easily.

• Type II: Individuals with fair skin, light-colored hair, and hazel, green, or blue eyes. They can tan with some difficulty but are prone to frequent sunburn.

• Type III: Individuals with average skin, regardless of eye or hair color. They tend to tan gradually and sometimes face mild sunburn after sun exposure.

• Type IV: Individuals with brown skin who tan easily and rarely experience sunburn.

• Type V: Individuals with dark brown skin who tan very easily and seldom develop sunburn.

• Type VI: Individuals with black skin who rarely experience sunburn and tan effortlessly.

Generally, light or very light peels are suitable for all Fitzpatrick skin types. A female with fair skin and blue eyes is an ideal candidate for medium or deep chemexfoliation. However, it is crucial to be cautious with Fitzpatrick skin types III to VI patients, as they may be more susceptible to aberrant pigmentation or dyschromia.[14][15]

An alternative approach to categorizing skin is the Glogau classification, which evaluates photoaging, as mentioned below.[13]

• Type I: Individuals with minimal to no wrinkling but with early aging changes.

• Type II: Individuals with developing smile lines.

• Type III: Individuals with noticeable wrinkles even at rest.

• Type IV: Individuals with widespread and evident wrinkles.

Male patients often require special considerations due to their thicker skin, which can lead to less predictable peeling outcomes.[6] Pre-peel spot testing offers a reliable means of predicting outcomes. Although not a routine procedure, some clinicians choose to conduct pre-peel spot testing to assist in selecting the most suitable peel for the patient.

To ensure effective peeling, the clinician should initiate a priming process. This preparation should commence 2 to 4 weeks before the procedure and involves the application of a topical agent on the skin. This process thins the stratum corneum layer, thereby enhancing the depth of penetration.[11] A frequently prescribed priming agent is all-trans retinoic acid, or tretinoin, typically in the form of 0.025% to 0.05% cream. Alternative options encompass salicylic and glycolic acids at concentrations ranging from 5% to 10%. For patients at risk of hyperpigmentation, a 2% to 4% hydroquinone cream can be used before and after the procedure to decrease postinflammatory pigmentary reactions. This is achieved by targeting and inhibiting melanocyte tyrosinase. In cases where patients have a history of herpes simplex viral infection, considering a course of acyclovir is advisable, and some authors even routinely prescribe prophylactic antivirals as a precaution.[16]

Clinicians should emphasize the critical need for protection against UV rays both before and after the treatment. Patients should steer clear of procedures that could potentially traumatize the skin, such as dermabrasion and waxing, before undergoing a peel. On the day of the procedure, patients must cleanse their skin and abstain from applying any skincare or makeup products.[13]

Technique or Treatment

Before commencing the chemical peeling treatment, it is essential to cleanse the patient's skin using a degreasing agent, such as isopropyl alcohol or acetone, to eliminate residual makeup or debris.[5] The patient should be positioned supine, with the head of the bed elevated to 45 degrees for the procedure.[11] A hair cap should be worn to keep the hair away from the treatment area. The clinician may choose to apply petroleum jelly to areas prone to potential chemical pooling, such as the nasolabial folds and lateral canthi. Adequate eye protection with appropriate shields should be provided to cover the eyes. General anesthesia is not typically necessary but might be a consideration for deep peels or highly anxious patients. Oral analgesics, such as acetaminophen, can be administered. In the case of deeper peels, opioid analgesics or a sedative may be required. 

The application process for light and medium peels generally begins on the forehead and temples, progressing to the cheeks and chin, with the areas around the eyes and mouth treated last. The chemical is evenly distributed using a brush, gauze, or a wooden spatula, with the choice of application method depending on the desired effect and the type of chemical peel used. Peel-specific application nuances can be considered. For instance, gauze sponges, which are more abrasive, may be suitable for liquid formulations. Furthermore, it is important to avoid overlapping brushstrokes to prevent an uneven outcome due to overconcentration of the agent. Feathering the edge of the treatment site can blur demarcation lines.[2][16] After applying the peel, glycolic acid should be neutralized using 5% sodium bicarbonate or cool saline compresses.

During a phenol peel procedure, phenol is typically applied only on a small portion of the skin at a time. The patient's face should be divided into sections and treated for approximately 15 min each. 

Specific areas requiring special attention include:

• Vigorously rubbing may be necessary for thicker keratoses, which can unevenly absorb the solution and frost. This additional effort aids in enhancing penetration.

• Stretching wrinkled skin to ensure an even coating within troughs and folds.

• Treating perioral rhytids using the wooden end of the cotton-tipped applicator, extending the application to the vermilion of the lips.

• Addressing deep wrinkles similarly to the surrounding skin, as these areas respond well to neuromodulators or fillers.

• Exercising caution when applying peel solution to delicate eyelid skin to prevent contact with the eyes or tears. Healthcare providers should gently roll a semidry applicator onto the lids and periorbital skin, carefully maintaining a distance of at least 3 mm from the lid margin.

After application, certain agents, such as TCA, can lead to frosting or whitening of the skin. Frosting can be categorized into 3 levels depending on the degree of protein denaturation. Level I frosting is typical during a light peel and is characterized by patchy frosting with mild erythema. Level II frosting occurs with a medium peel and represents a more homogeneous white coat of frosting with underlying erythema. In contrast, a deep peel achieves level III frosting, which manifests as a white, plaque-like formation with minimal visible erythema.

Desquamation typically concludes within several days and is followed by intense erythema, which gradually subsides over 1 to 2 weeks. After 24 hours, patients may shower and use a non-detergent face wash. Notably, it is crucial to re-emphasize the importance of sun protection and sunscreen application.[16] Patients should refrain from using makeup until their skin has fully healed.[5]

Post-Peel Instructions

After undergoing a chemical peeling procedure, patients are advised to follow the following post-peel instructions to ensure proper healing of their skin and achieve the best possible results:

• Individuals should avoid picking or peeling the desquamating skin.

• Individuals should steer clear of direct sun exposure.

• Individuals should use a gentle cleanser with a patting motion, avoiding rubbing or using a washcloth when washing their face in the morning and before bed.

• Individuals should gently pat dry with a towel after washing their face.

• After undergoing light peels, individuals are advised to apply a non-comedogenic moisturizer after cleansing. Individuals should also incorporate mineral-based sunscreen into their skincare routine in the morning.

• For medium and deep peels, Individuals are recommended to apply a moldable icepack or a bag of frozen vegetables for 10 min every hour for 1 to 2 days. After washing, they should use an unscented emollient by gently patting it on their face. In addition, they should apply an unscented, bland emollient to the desquamated areas 3 to 5 times daily.

• For deep peels, individuals should soak gauze in a mixture of 1 tsp of white vinegar with 2 cups of bottled water and apply it to their face for 10 min every 1 to 2 hours. These vinegar soaks are beneficial in reducing bacterial overgrowth on the moist, healing wound.

Complications

Deeper peels are associated with increased therapeutic effects and more significant risks.[17] Individuals with darker skin tones with a known history of hypertrophic scar formation are at the highest risk of complications. Recent or ongoing exposure to isotretinoin can adversely affect the outcome of a chemical peeling treatment. Therefore, patient selection and counseling are crucial in maximizing results and minimizing complications. Furthermore, it is imperative that patients strictly adhere to post-peel care instructions, with particular emphasis on sun avoidance, to optimize their outcomes.[1]

Complications from chemical peeling can be classified as immediate or delayed. Immediate complications occur during or shortly after the procedure, while delayed complications may occur weeks or even months later.

Immediate Complications 

Immediate complications include skin edema, burning and itching sensation, blistering, anaphylaxis, ocular mucosal splashes, cardiac arrhythmias, and systemic toxicity or salicylism.[18][19]

Delayed Complications

Delayed complications include bacterial, viral, or fungal infections; acne and milia eruptions; postinflammatory hyperpigmentation; hypopigmentation and lines of demarcation; and incomplete responses.[14][18]

Notably, before phenol peeling, it is advisable to conduct liver and kidney function testing to diminish the risk of toxicity. Salicylism, although infrequent, is a complication characterized by symptoms such as tinnitus, nausea, vomiting, dizziness, psychosis, stupor, coma, and death in severe cases.

Clinical Significance

Chemical peels for skin resurfacing are a potent method to rejuvenate the aging face, bestowing a more youthful and rested appearance. In addition, chemical peels are often used with medications to combat acne and effectively address potentially precancerous actinic keratosis. The primary objective is to achieve even pigmentation and minimize textural irregularities. Skin resurfacing through chemical peels seeks to improve a patient's overall appearance, thereby enhancing their self-esteem.[20][21]

Enhancing Healthcare Team Outcomes

Identifying the risk factors and conducting a comprehensive patient assessment before proceeding with a chemical peel is imperative. Adopting an interprofessional team approach is optimal for enhancing overall outcomes and mitigating complications associated with facial peels. Only an experienced healthcare professional should evaluate patients for chemical peeling treatment If anesthesia is warranted, it is essential for both a primary care clinician and an anesthesiology specialist to assess the patient's suitability. In the case of phenol peels, conducting liver and kidney function tests can help minimize the risk of toxicity.

To achieve the best possible results, an interprofessional team of aestheticians and healthcare professionals with specialized training should be readily available before, during, and after the chemical peeling procedure. Healthcare professionals performing the chemical peeling procedure must possess the expertise to choose and apply the appropriate chemical peel. They should also be able to recognize potential complications for minimizing morbidity and mortality rates in patients.

In the immediate postoperative phase, it is essential to have close monitoring by a healthcare team who are experts in post-procedural care for chemical peels. Their role involves vigilant monitoring of the patient for any potential complications. The healthcare team must provide coordinated patient education on proper post-peel skin maintenance and explain the importance of minimizing sun exposure during the initial weeks after the procedure. This approach is crucial for achieving optimal results and preventing complications. In this regard, a well-trained, cohesive interprofessional team can be invaluable in improving overall patient outcomes.

Nursing, Allied Health, and Interprofessional Team Interventions

Over-the-counter pain medications are generally sufficient to manage post-procedural facial discomfort. To reduce erythema and dryness, patients should follow the 0.25% acetic acid soak procedure as previously described and apply petroleum jelly several times daily until the treated area completes its peeling, which usually takes around 5 to 10 days. Although intense erythema may be present immediately after skin desquamation, it gradually diminishes over several days.

Patients are strongly advised to refrain from direct sun exposure during the first several days after the procedure. Protective measures should be implemented for several weeks to months, including using sunscreen and wearing wide-brimmed hats outdoors. Makeup may be applied again after approximately 1 to 2 weeks once re-epithelialization is completed, and the skin is healed and healthy.[5] Close follow-up after the procedure is recommended to assess for any potential complications. If the patient wishes, photographic documentation should be conducted approximately 2 to 3 months postoperatively.

Nursing, Allied Health, and Interprofessional Team Monitoring

Close follow-up during the initial postoperative period is crucial, and this monitoring can be conducted by a wound care nurse and a clinician experienced in the post-procedural care of skin resurfacing with chemical peels. This ongoing evaluation should be comprehensive, assessing potential complications ranging from localized skin reactions to systemic cardiotoxicity.[5]