Dr Simon Ravichandran discusses the properties and use of medium and deep chemical peels
Chemical peels are treatments that aim to improve the skin of the face or body by using a chemical solution, resulting in controlled destruction at a specific level of the skin. The result is usually a sloughing off of dead skin with regeneration of newer healthier tissue. The regenerated skin is typically smoother, less wrinkled and has less pigmentation and blemishes than the old skin. Chemical peeling in dermatology has been practised from the early 1950s with the use of phenol in the treatment of acne scars. The techniques have evolved over time with the development of other peeling solutions such as trichloroacetic acid (TCA) and alpha-hydroxy acids (AHAs), which penetrate to different depths and elicit different results with an improved side effect profile and shorter recovery periods.1
In the field of aesthetic dermatology, the chemical peel is a common procedure due to its efficacy in reversing the cutaneous stigmata of ageing such as wrinkling, sallow complexion, pigmentation and cutaneous laxity.1 The aesthetic practitioner requires a detailed understanding of the different types of chemical peel, the mechanisms of action, expected results and potential undesired outcomes, as well as cautions and contraindications in order to select the appropriate treatment for the appropriate patient. For the non-dermatologist aesthetic practitioner, the choice of peels from a wide number of companies is often confusing and training is typically focused on specific products, rather than general concepts. This again reinforces the necessity for further research and learning on the properties and use of chemical peels.
Chemical peels are currently classified according to the depth of penetration and injury caused. Superficial peels penetrate to any depth within the epidermis, down to the stratum basale, medium-depth peels penetrate through to the papillary dermis, while deep peels penetrate down to the level of the reticular dermis.2 Superficial chemical peels may be further subdivided into very superficial and superficial, with very superficial peels only affecting the stratum corneum.2
The peeling solution used does not necessarily determine the depth of peel. Depth can be determined by a number of factors including the concentration of the solution, the pH, the availability of free acid, the length of time applied to the skin, the condition of the skin, and the method of application.3 For example, a glycolic acid 70% solution may act as a superficial peel when applied for five minutes, however it can cause a medium peel effect if left for 15 minutes. TCA in various concentrations can be used as a superficial, medium or deep peel.
A more recent development in the evolution of chemical peeling has been the combined peel approach, where different agents are used sequentially for a synergistic effect and lower side effect profile. Examples include the Jessner’s TCA peel and the 70% glycolic acid peel, prior to 35% TCA.
It is considered essential nowadays for patients to have a regime of skin preparation prior to undergoing any chemical peel. The purpose of this is to reduce the likelihood of undesired sequelae such as post-inflammatory hyper-pigmentation (PIH), to allow for a more effective rejuvenation and to identify any potential issues with products that may be used either during or after the peel. Typical regimes will include a low concentration alpha hydroxy acid cleanser or moisturiser, retinol/isotretinoin and/or a skin-lightening agent such as hydroquinone, kojic acid or similar. The use of a sunscreen is also included to aid the reduction of melanocyte excitability. Preparation of the skin is generally advised for a minimum of two weeks prior to peeling.
Medium depth chemical peels are indicated in the management of fine lines and wrinkles associated with photoageing, as well as pigmentary disorders and superficial atrophic scars. The traditional medium-peeling agent was TCA in concentrations of 40% to 60%. This was effective, however it did have a higher risk of complications such as scarring and pigmentation.4 Nowadays, similar results are achieved using 35% TCA solutions in combination protocols, typically with Jessner’s, 70% glycolic acid or solid carbon dioxide. These combination treatments have been found to produce the same results as 50% TCA but with fewer risks.4
Jessner’s solution consists of 14g salicylic acid, 14g lactic acid and 14g resorcinol; made up to 100ml with ethanol.5 Prior to application the skin is cleansed and thoroughly scrubbed with acetone in order to remove sweat and sebum. Curettage may also be performed to hypertrophic actinic keratoses at this stage. The peel is applied to cleansed and degreased skin using a cotton applicator to achieve an endpoint of a speckled white frost and uniform erythema. After application, and once the endpoint has been reached, cool water compresses may be applied to help soothe the burning discomfort that occurs with Jessner’s peel. This application serves as a keratinolytic, altering the permeability of the epidermal barrier to permit a more even and rapid penetration of the TCA solution.6 After the Jessner’s solution has been washed off, a topical anaesthetic such as EMLA or LMX may be applied to improve the patient’s comfort during the TCA peeling process.
After the skin has been cleansed of any topical anaesthetic and dried, 35% TCA is painted onto the skin uniformly using cotton-tipped applicators or small gauze swabs. The end point is identified as a uniform white frosting with a background erythema. Cool compresses are then applied to help soothe the burning sensation that subsides over the next 10 minutes. When the discomfort has resolved completely an occlusive ointment such as Vaseline or Aquaphor is typically applied. These simple ointments serve to reduce some of the dryness of the skin post treatment.
This approach has the same benefit as the Jessner’s technique but uses glycolic acid as an alternative initial superficial peel. The glycolic acid is keratinolytic and allows for greater penetration of 35% TCA.7 Typically, it is applied for two minutes prior to neutralising with bicarbonate solution or cool water. 70% glycolic acid is not suitable for inflamed or dry areas of skin, as the penetration is increased in these areas and may give rise to an inadvertent medium depth peel.8
This technique involves using a solid block of CO2 coated with acetone and applied to the skin to create an epidermal injury. The depth of epidermal injury created is related to the time the CO2 is applied, as well as the depth of penetration and peel that will occur with the subsequently applied TCA solution. Thus, areas that require deeper peeling, for example, deeper wrinkles, scarring and thick actinic keratosis, may be pretreated with a prolonged application for a better peeling outcome. The advantage of this technique is a greater aesthetic improvement, however, it is important to note that the results are operator and technique dependent.
The main medium depth peeling agent, TCA, acts as a protein denaturant. TCA is a water soluble agent that does not penetrate easily in the lipid rich sebaceous skin, thus the role of skin preconditioning and superficial peeling, prior to application of the TCA, is to thin and increase the permeability of the stratum corneum and remove oils from the surface of the skin. This allows for a deeper and more even penetration, as well as a more even and consistent depth of protein denaturation.9
Immediately after a medium depth chemical peel, the patient’s skin can be swollen and can feel tight. Continuous application of occlusive ointments several times a day is recommended by some practitioners. We adhere to this principle in our clinics; finding a reduction in recovery times with less incidence of prolonged erythema following medium depth peels. The epidermis above the level of chemical injury will separate from the underlying skin from approximately the third day, and there will be some associated serous exudate and crusting. The skin tends to start to peel from the perioral area and radiate out to the whole face, with the forehead peeling last.
Patients are advised not to pick at the exfoliating epidermis as this may cause scarring, however they can trim off the dead skin with sharp scissors. A moisturiser may be applied after five days and the peeling process may continue for ten days. After the epidermal peel layer has cleared, patients usually notice the new skin is brighter and more even. Pigmentation and blemishes should have reduced and fine lines and wrinkles should have effaced. There is an ongoing process of dermal remodelling that results in neocollagenesis after about six weeks, providing an ongoing improvement in skin quality.10 Depending on the degree of photodamage and ageing, further peels may be recommended to continue the rejuvenation. The patient’s pre-treatment skincare regime can be reinstated after three weeks.
When deep peeling is discussed in the literature, it generally concerns the use of phenol. TCA at concentrations of greater than 50% have been employed, however the incidence of complications with such a high concentration can make phenol a more attractive alternative.11
Like TCA, phenol works by penetrating through the skin and causing denaturation and coagulation of proteins at a specific depth in the dermis. Unlike TCA, phenol penetrates the skin quickly through the skin to the reticular dermis. Phenol peels are therefore described as a quick peel, which allows for less adjustment over the depth than can be achieved with TCA.12
Phenol has been used as a peeling agent for several decades and a number of formulations have been used. Originally, undiluted 88% phenol was used as a medium depth agent, however the Baker- Gordon formula described in 1961, which combines phenol with water, septisol soap and croton oil allows a deeper penetration than pure phenol alone. Further modifications of the formula were described by Stone and Venner-Kellson, whereby the concentrations of the croton oil were modified and additional agents such as olive oil and glycerin were added.13 Whichever phenol preparation is used, if the result is a reticular dermis protein coagulation, the end result will be the same.14 The indications for deep peeling are therefore moderate to severe wrinkles, dyschromias and acne scars. As the epidermolysis with a deep peel is complete and also involves the papillary dermis, it will achieve a far better improvement in rhytids and pigmentation than a medium depth peel, which only penetrates to the papillary dermis.
A deep phenol peel carries more risk than medium depth peels as, not only does the increased depth of dermal injury associate with a higher incidence of scarring, delayed healing, PIH, and hypo-pigmentation, the phenol itself is systemically absorbed and is cardiotoxic, thus carrying a risk of heart failure.15 The risk is related to the volume of phenol used and, thus, when a full facial treatment is performed it is undertaken in sections, with one area being completed before moving onto the next. For full facial treatment with phenol, cardiac monitoring in an appropriate clinical environment is highly recommended. Antiviral and antibiotic cover is required during the procedure, and oral steroids are also often administered.
Phenol peels induce an intense discomfort and are sometimes performed under general anaesthetic for this reason. At the very least, either oral or intravenous sedation is used pre-, intra- and post-operatively. For the procedure, the skin is cleansed and degreased in the same fashion as for a medium peel. The phenol solution is applied to the skin using rolled and rung gauzes to an area. When one area has been treated the solution is washed off and the next area is treated. The end point for a deep peel is identified as a frost of coagulated protein that is a grey-white colour, the loss of erythema within the frosting indicates the peel has progressed beyond the vascular loops of the papillary dermis.6
The recovery period from a deep phenol peel is longer and more involved. An occlusive dressing such as a waterproof tape mask is employed for the first 48 hours. The skin at this point is wet and exudative and requires careful wound care, with applications of thymol iodide several times daily for a further week. During the first week, movements of the perioral area can crack the developing wound so patients may be advised to limit mouth movements by ingesting a blended diet through a straw. Epidermal re-epithelialisation should occur by approximately day nine, and the dead peel mask can be gently debrided with regular warm compresses and emollient applications. The new skin will be erythematous and swollen and, for very deep peels, can persist for up to four weeks. Phenol peels result in a dramatic and long lasting improvement in facial rhytids, texture and pigmentation.16
Whilst medium chemical peels usually produce excellent results, there are a number of complications that can occur. Careful patient selection, appropriate choice of peel, pre-treatment and close observation of endpoints should all reduce the rates of occurrence of complications. Erythema following medium depth chemical peeling is common and should fade within three to four weeks. Sometimes the erythema will be prolonged and may be an indicator of contact sensitisation, prior skin disease (rosacea/eczema) or an inadvertent deeper depth of peel. Scarring is uncommon following medium depth peels but may occur several months after the peel. It may be spotted early by the identification of areas of intense and prolonged erythema and induration. Early and prompt treatment with topical steroids may be of value.17
Development of herpetic lesions is common and more common in patients with a history of herpetic lesions.17 This should be specifically enquired for in the patient history and antiviral prophylaxis should be prescribed to patients who are at risk. Some practitioners routinely prescribe antiviral medication as a matter of course to all patients undergoing chemical peels. Infections following medium depth chemical peels are uncommon and should be identified early in the recovery phase due to a greater than expected erythema, pustules, excessive crusting and pain.
Swabs for bacteriology, mycology and virology should be taken and empirical treatment commenced pending lab results. Permanent hypo-pigmentation is a complication of peeling and more likely to develop in darker skinned individuals after deeper peels. This may be related to other complications such as infection in the recovery period. PIH is also a risk and, as with hypo-pigmentation, is more likely to occur with deeper peels and patients with pre-existing pigmentation problems. The risk can be reduced by appropriate pre-treatment preparation and, if it occurs, can be managed with the topical application of 4% hydroquinone.18
Risk factors for complications should be identified in the pre-treatment stage and high-risk patients should be dissuaded from treatment. Risk factors include cigarette smoking, poorly controlled diabetes, immunocompromised status, recent facelift or laser resurfacing, a history of recent or current herpes simplex infections and a history of hypertrophic and/or keloid scarring. A history of isotretinoin use should also be enquired for, as use within the preceding six to twelve months is associated with an increased likelihood of scarring.18
The patient requesting rejuvenation procedures for the reversal of skin ageing has a number of options. The first step in the consultation is to address the degree of photoageing and the desired outcome. The two assessment scales of importance are the Glogau scale of photoageing19 and the Fitzpatrick classification20 of skin type. The Glogau scale is an indicator of the degree of damage and will point towards the correct peel type; for example, type II and III would benefit from medium peeling and types III and V would benefit from deep peeling. There would be little advantage in offering a deep peel to a Glogau scale II patient and not much improvement would be seen with a medium peel in a type IV patient. The Fitzpatrick classifies skin types into their colour and their reaction to sun exposure. It is a good indicator of the behaviour of melanocytes and a predictor of the chances of PIH, hypopigmentation and scarring. Darker skin types are more prone to these complications and peeling needs to be undertaken with caution and respect.
A patient history will also help direct the treatment as there are a number of contraindications that would preclude a deeper peel, for example hepatic and renal impairment, history of scarring, previous surgery or radiation treatment. Due to the cardiac toxicity associated with phenol peels a detailed cardiac history should also be obtained.
The patient undergoing a peel needs to understand and be involved in his or her own care as there is a degree of pre-treatment and post-treatment wound care that is essential to the outcome. For patients less motivated, or for patients less willing to undergo a prolonged recovery period, a medium depth peel repeated every six months to a year would be a more sensible option than a single deep peel. The risk benefit profile also needs to be considered by the patient, as they need to be able to justify the higher risk of the phenol peel with the potential greater outcome, and vice versa for the medium depth peel.
The final consideration when choosing a treatment is the experience of the practitioner performing the procedure. The procedures are practitioner dependent, as an experienced practitioner who has performed hundreds of deep peels is likely to get a better result, with a lower risk profile, than a novice. The medium peeler with considerable experience will also be able to achieve better results than a novice medium peeler, as they will be more familiar with a number of skin types and be able to match the end point to the desired outcome more easily. The practitioner beginning their journey in chemical peels should therefore make every effort to direct their learning and training towards gaining a thorough understanding of skin physiology and anatomy, modes of action of chemical peels and perform as many chemical peels, under the supervision of an experienced peeler, as possible.
Phillip A. Stone., ‘Phenol Peeling: Chemical Peels’, Procedures in Cosmetic Dermatology, 2nd edition, pp.71-87.
David M Duffy, ‘Avoiding Complications: Chemical Peels, Procedures in Cosmetic Dermatology’, 2nd edition, pp.151- 171.
Kyle M. Coleman, William P. Coleman III, ‘Complications: Chemical Peels’, Procedures in Cosmetic Dermatology, 2nd edition, pp.173-180.
TC Fischer, E. Perosino et.al., ‘Chemical peels in aesthetic dermatology: an update’, 2009 JEADV, 24 (2010), pp.281-292.