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Chemical Peels
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INTRODUCTION
Chemical peeling is a controlled wounding in which chemical agents are painted on the skin to produce superficial peeling. With healing, irregularities of contour, texture, and coloration are less apparent. This technique is used for a variety of conditions but primarily for treatment of wrinkles, sun damage, excess pigmentation, and actinic keratoses (”sun spots”). The key to understanding chemical peeling is for one to appreciate that various chemicals, in particular concentrations or formulations, will penetrate and injure the skin to variable predictable depths. In performing chemical peeling, the cutaneous surgeon must determine to what depth the skin pathology extends and match the appropriate peeling agent with the condition.
TYPES OF CHEMICAL PEELS
Light chemical peels, which remove the very outer layers of the skin (stratum corneum), have traditionally been used as exfoliants in the treatment of acne and excessive oiliness of the skin.
Medium depth peels, which extend into the papillary dermis, are effective in managing the textural and pigmentary changes that accompany early photoaging of the skin. Superficial wrinkling, scattered lentigines, and early actinic keratoses are all effectively managed by peeling agents which injure the upper dermis.
Deep chemical peeling, which extends into the deeper (reticular dermis), has been used for treating more advanced photoaging changes, in particular deep wrinkles and severe solar elastosis. In modern times, this type of peeling has been largely replaced by CO2 laser resurfacing.
TRICHLOROACETIC ACID PEELS,
Trichloroacetic acid (TCA) peeling has become a popular technique for treating less advanced photoaging. The frequency of adverse reactions is low and the chemical is free of major side effects. The depth of penetration and resultant tissue damage varies with the concentration of TCA used. Light "freshening washes" using 10-20% TCA are effective in the treatment of acne or excessive oiliness. TCA used in concentrations of 35-45% yields medium depth damage into the papillary dermis while 50% TCA will produce a deeper peel that extends to the reticular dermis. Occasionally, adjunctive chemicals, such as dry ice or Jessner's solution (see below) are used in combination with the TCA to enhance its penetration.
Anesthesia is not generally employed for TCA peeling, although some cutaneous surgeons administer a pre-operative sedative, amnesic, or analgesic. The skin is first thoroughly degreased with acetone which is applied gently to the face with a gauze pad. Once the skin has been thoroughly cleansed, the TCA is applied evenly over the skin surface. Within a minute or two of applying the chemical, frosting becomes evident. This is accompanied by short-lived discomfort which is perceived as a "burning" sensation accompanied by a tight feeling or "drawing" of the skin. For full face TCA peels, the discomfort persists for approximately 7-10 minutes and its severity varies with the concentration of acid used. The use of an electric fan to circulate air over the face immediately after chemical application significantly lessens the amount of burning perceived by the patient. The feeling of tightness is rapidly and significantly reduced by the application of a thin layer of antibiotic ointment at the completion of the procedure. The immediate use of cool wet compresses on the treatment sites is soothing for some patients but may actually increase the discomfort in others. Frosting is replaced by erythema in about 30 minutes.
Superficial TCA Peels
Low (10-20%) concentrations of TCA cause superficial exfoliation and a comedolytic action which is helpful in the management of acne. Shortly after application of the peel solution, a faint frosting of the skin will appear. There may be a small amount of burning but the discomfort is easily tolerated by most patients. Redness and superficial peeling of the skin are seen within the next 48 hours and healing is usually complete within two to four days. The skin is sensitive for approximately one week after the peel, during which time acne medications should be discontinued.
Very light TCA peels of this type are also helpful for treating oily skin and skin with prominent pores. The effects, as with other keratolytic and desquamating agents, are only temporary and, as a result, TCA "washes" may be repeated every few weeks or months as needed. Textural improvement may occur, over time, with repeated applications.
Medium Depth TCA Peels
Medium depth peels with 35-45% TCA yield improvement of skin texture, pigmentary alterations, and other changes of photoaging. Early actinic keratoses are also effectively removed in this manner although hypertrophic lesions are relatively unaffected. As expected, there is more peeling, inflammation, and swelling than is seen with superficial peels. When the areas around the eye are peeled, eyelid swelling can be severe enough to shut the eyelids.
The Jessner's Medium Depth TCA Peel
Relatively low concentrations of trichloroacetic acid can cause deeper injury when combined with other exfoliants that enhance the penetration of TCA into skin. Jessner's solution (Coombes' Formula), used years ago as an exfoliant for treating acne, has recently been used successfully for this purpose. The solution consists of 14% each of Lactic Acid, Salicylic Acid, and Resorcinol mixed in 95% ethanol. After cleansing the skin with acetone and prior to application of the TCA, the skin is painted with Jessner's solution, using a folded gauze pad. A small amount of frosting will appear, particularly over thickened or rough skin areas. Some peeling of the outer skin layers (“keratolysis”) is presumed to occur, allowing for deeper penetration of the TCA which is applied in 35-45% concentration. Brody has reported the use of solid carbon dioxide as an adjuvant for TCA peeling which serves to enhance the depth of peeling in much the same way as Jessner's solution.
Postoperative Management of TCA Peels
Patients leave the office with a thin layer of antibiotic ointment (Fucidin Ointment or Polysporin Ointment) applied to the treatment site. No dressing is required. The chemical burn and accompanying pain is complete and over the next 48-72 hours the skin will begin to peel much as it would following a severe sunburn. Patients are instructed to keep the treatment site covered with a thin layer of antibiotic ointment at all times, including at bedtime. Patients may get into the shower and wash the treatment site as often as they wish as long as they reapply the ointment afterwards. They may gently massage away any skin that has entirely loosened but are instructed not to attempt to peel off any adherent skin.
We usually prescribe a one-week prednisone taper to minimize swelling and discomfort that usually takes the form of itching. The dosage begins at 40 mg (8 pills) the first day, and diminishes by 5 mg (one pill) on each successive morning. Patients are seen at 7 days and, at that point, most if not all of the injured skin has separated and a pink regenerated base is present.
The skin may remain red, like a mild sunburn, for an additional 4-6 weeks. During this time, make-up and sunscreen may be applied daily to cover the redness and protect the newly-formed skin from sun damage.
Potential Complications from TCA Peeling
Occasionally, scattered non-healed areas may be present, signifying that a deeper injury was sustained in this location, presumably due to uneven uptake of the acid. Care should be taken to keep any non-healed areas covered with antibiotic ointment as healing proceeds. Scarring may result in such areas, usually in the form of slightly depressed scars with thread-like margins. Occasionally, hypertrophic (thickened) scarring occurs, and is treated immediately with injections of cortisone into the scars.
In addition to scarring, other potential complications that can occur as a result of TCA peeling include infection and changes in the skin colour, either lighter or darker. Infections are usually due to bacteria but can also be due to the virus that causes “cold sores”. Patients who suffer from frequent cold sore outbreaks are placed on anti-viral medication prior to chemical peeling, in order to lessen this possibility. Colour changes may be temporary or permanent in nature but fortunately are uncommon following TCA peeling. Skin lightening, if it occurs, is usually permanent. The use of sunscreens following peeling is helpful in preventing darkening of the skin colour.
GLYCOLIC ACID PEELS
Glycolic acid "peels" have become quite popular for treating acne, minimal sun damage, pigmentary change and textural irregularities. In fact, these are not really "peels" at all but are better referred to as "washes". Various concentrations of glycolic acid (up to 70%) have been used for this purpose. Usually, a series of 6 "peels" delivered two to four weeks are combined with twice daily use of a glycolic acid cream (NeoStrata or Reversa). I have found that the results are quite subtle, even after several treatments and that significant melasma is not improved with this treatment. Mild pigmentary changes may improve. Some smoothing of the skin texture is generally achieved, but again this is subtle. Pore size decrease has been noted in a number of our patients and acne seems to improve. There are no pigmentary problems noted, making this a safe modality for use in darker skins.
SUNSCREENS
All patients undergoing chemical peeling for photoaging are, of course, instructed in the use of sunscreens. They are advised to begin using sunscreens with a Sun Protection Factor (SPF) of at least 30, on a daily basis under their makeup, as soon as healing is complete.
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