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Deep Chemical Peels
The results of phenol–croton oil peeling, also known as deep chemical peeling, are considered the gold standard in the treatment of the aged face. Historically, in the “pre–energy-based devices era,” it was almost the only option for radical facial skin rejuvenation. The main advantages of a deep peeling procedure are its efficacy, predictability, and longevity of results. The dissection of phenol–croton oil formulas discloses that more than one formula is safe and effective. The success of the procedure depends on the surgeon’s qualification, the patient’s education, and adhering to safety standards.
History
Almost all the modern formulas for deep peeling contain phenol and croton oil. The early use of phenol peel was documented by two dermatologists, George Miller MacKee and Florentine Karp, in their publication on treating patients with postacne scars. The first time that croton oil was mentioned as an ingredient of deep peeling solution was by Adolph M. Brown, in his 1959 patent application entitled “Skin Treating Method and Composition.” Among other contributors to the medical development of phenol–croton oil peels at that time were Bames, Urkov, Combes et al., Brown et al., and Litton.
The final revival of deep chemical peeling is attributed to two American plastic surgeons, Thomas J. Baker and Howard L. Gordon, who during the 1960s legitimized this procedure by discussing it in national meetings and demonstrating their impressive results. The scientific landmark breakthrough in phenol–croton oil peeling came from a publication of Gregory Hetter, who showed that by varying the amount of croton oil in the peel solution the strength of the peel can be modified. Other authors, such as Stone and Lefer, Spira et al., and Fintsi, contributed to the procedure, allowing it to emerge from semiobscurity to its respectable and valued place in a field of aesthetic surgery.
Chemical Background
The active ingredients in the solution for deep peeling are a combination of croton oil and phenol.
Phenol (C5H5OH), or carbolic acid, is an aromatic hydrocarbon derived originally from coal tar, but prepared synthetically in a process that uses monochlorobenzene ( Fig. 8.1 ). After this process, 98% phenol appears as transparent crystals, and the liquefied phenol consists of 88% USP solution of phenol in water.
Croton oil is an extract of the seed of the plant Croton tiglium and has been commercially prepared as croton resin since 1932. Its activity on the skin is related to free hydroxyl groups, which cause skin vesiculation even in low doses.
Other ingredients in deep chemical peel formulas include Septisol or Novisol, water, and vegetable oils (glycerin, olive, sesame).
Formulations
The concentration of phenol in different formulations ranges between 45% and 80%, whereas croton oil is between 0.16% and 2.05%. The role of Septisol is to reduce the skin surface tension and to improve solution penetration. Despite this, Septisol is not included in all of the formulas. Some of the formulas contain oils. The role of the oils in the formula has not been clarified yet. Our personal experience shows that oily phenol solutions penetrate the skin in a more controllable fashion.
Few dogmas regarding phenol-based peeling solutions have been challenged in the last two decades. The concept of the “all-or-none” effect of the Baker-Gordon formula on the skin was confronted by Gregory Hetter, who showed that depth of the penetration and clinical outcomes of the peel can be manipulated by a change in the amount of croton oil. A major advantage of this concept is that by decreasing the croton oil concentration, the surgeon is able to accommodate the depth of the peel according to the skin type, area treated, or expected clinical outcome, by changing the amount of the solution applied and the number of coats.
Histology
Biopsies obtained 48 hours after phenol peeling demonstrate necrosis of the epidermis, extending through the papillary dermis, surrounded by a marked inflammatory reaction. Epidermal regeneration is completed within 7 days, whereas dermal healing usually lags behind. Histological changes in human skin induced by deep chemical peeling include a newly formed band of dermis found directly beneath the epidermis consisting of horizontal compact bundles of collagen and a dense network of fine elastic fibers, as well as even and uniformly shaped keratinocytes in epidermis. Although peeled skin tends to be hypopigmented, melanocytes are present. These changes are evident even as long as 20 years after the peel.
Indications and Patient Selection
The main indications for deep chemical peels include dyschromia, especially solar lentigines; wrinkles; solar keratosis; and acne scars. Deep peels can be used to treat periorbital melanosis, benign skin growths, or deposits, such as xanthelasma or epidermal nevus. Recently, the efficacy of phenol–croton oil peels was shown for lip enhancement.
Thick male skin is usually less responsive to deep peels, but men with severe actinic damage or acne scarring benefit significantly from the procedure.
Deep peeling can be performed on the eyelids to improve excess eyelid laxity, periorbital pigmentation, or wrinkling or as an adjunct procedure to surgical or micropunch blepharoplasty.
A combination of deep peeling performed on one cosmetic unit with a medium-depth peel performed on the rest of the face is called a segmental peel. Segmental peeling is a procedure of choice if a limited area (usually perioral or periorbital) is significantly more wrinkled than others ( Fig. 8.2 ). Use of deep chemical peels on an area smaller than 1% of the body area does not require cardiac monitoring.
Contraindications
There are few absolute contraindications for deep peeling, mainly physical or mental instability. Originally, the ideal patient for a deep chemical peel was a blond, blue-eyed, fair-complexioned woman. Our experience shows that phenol-based peels can be safely performed on olive- and dark-skinned patients with dark eyes and hair. As long as a patient is aware and cooperative in using a skin-lightening preparation (see Chapter 3 ) and potent sunscreens during the postpeel period, the procedure is equally effective and safe for dark skins.
During pregnancy and lactation, any cosmetic intervention is considered to be undesirable. Although patients with controlled hypertension, diabetes mellitus, and thyroid malfunction can be peeled safely, any preexisting heart condition requires special precautions. All patients are required to have an electrocardiogram before the procedure. Medications prolonging QT interval should be stopped or switched before the procedure, because QT interval prolongation has been reported during phenol–croton oil peels. It is always recommended to work in cooperation with a patient’s cardiologist.
Systemic isotretinoin (Accutane) used to be an absolute contraindication to any cosmetic intervention. This approach has been recently challenged. We feel that minimal interval to peeling after stopping this medication can be shortened from the traditional 6 months, especially when performing a procedure on a patient with thick sebaceous skin.
According to our experience, smoking does not adversely affect the postpeel healing or the extent of the results. We suggest adding frontal fibrosing alopecia (FFA) as a relative contraindication for the procedure. Once a rare disease, FFA has recently become a prevalent condition. Inflammation and fibrosis of the hair follicles in facial skin, as happens in this disease, may affect the healing process after deep peeling.
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