Glycolic Acid

Glycolic acid, an AHA, has become one of the most widely used organic carboxylic acids for skin peeling. Glycolic acid formulations include buffered, partially neutralized, and esterified products. Previous studies have recommended the use of a buffered or partially neutralized glycolic acid, which is safer than free glycolic acid.

Concentrations for peeling range from 20–70%. The intensity of the peel is determined by the concentration of the acid, the vehicle used, the amount of acid applied and the technique used to deliver the acid. Increasing strength yields a deeper peel, and both superficial and medium-depth peeling may occur with glycolic acid. Some studies have reported dermal scarring when a 70% glycolic acid solution was left on for 15 minutes.

Overall, glycolic acid is an excellent peeling agent for skin of color. Some authors have shown a great improvement in skin texture and acne of patients treated with a series of 35–70% glycolic acid peels. Although some studies have demonstrated a greater efficacy of glycolic acid peels in treating melasma in darker-skinned groups, we find it less desirable as a peeling agent for melasma and PIH because it may actually induce PIH in skin types V and VI. A skin test on a representative area is highly recommended before perform the peel.

In general, glycolic acid peels are well tolerated in darker skinned people. Side effects are substantially minimized when peel concentrations are gradually titrated from the lower concentrations of 20–35% to the full-strength 70%. Glycolic acid peels are most advantageous when treating darker skin types with sensitive skin.

Salicylic Acid

This acid is a lipophilic agent that produces desquamation of the upper lipophilic layers of the stratum corneum. A study by Grimes showed a moderate to significant improvement in treating acne vulgaris, PIH, oily skin, textural changes, and melasma in dark skin patients, with minimal to mild side effects. Another study by Lee et al also demonstrated greater efficacy of salicylic acid peel in treating acne in darker phototypes. Previous studies also have noted enhanced improvement of oily skin, enlarged pores, and acne vulgaris with the use of salicylic acid peels compared with glycolic acid peels.

Jessner’s Solution

Jessner’s solution contains 14% resorcinol, 14% salicylic acid and 14% lactic acid. It has been used alone for superficial peeling, or in combination with TCA 35% for medium-depth peeling.

In general, these peels are well tolerated. As with glycolic acid and salicylic acid peels, Jessner’s peels are most commonly used as adjunctive therapy for moderate to severe facial dyschromias, acne, oily skin, texturally rough skin, fine wrinkles, and pseudofolliculitis barbae.

When compared to 70% glycolic acid peels, no difference was found with respect to the frequency of side effects in patients of skin types IV–VI. However, the phenolic compound, resorcinol, may cause some depigmentation problems in skin types V and VI.

Trichloroacetic Acid (Tca)

In skin of color, the desired performance with this agent is a superficial peel; therefore, concentrations of 10–30% are utilized. TCA precipitates epidermal proteins and causes necrosis. The extent of damage, as well as the risk of postinflammatory dyschromias and scarring increases with higher concentrations.

TCA peels are much less predictable for skin types IV–VI in comparison to glycolic acid, Jessner’s solution, and salicylic acid. The frequency of postpeel hyperpigmentation is significantly higher in dark skin. When conditions such as wrinkles, photodamage, and stubborn pigmentation are recalcitrant to glycolic acid, salicyclic acid, or Jessner’s peels, most authors will consider TCA peels. Although the standard endpoint of a TCA peel is a white frost, in skin types IV–VI, a frost is not desired because it enhances the risks of postpeel dyschromia and scarring.

Premixed Commercial Combination Peels

The Vi Peel^™ is recommended for use in darker skin types. The Vi Peel^™ is available as a premixed formula containing TCA (9% in alcohol), phenol (9%), salicylic acid (9%), tretinoin (0.1%), and 4% vitamin C (with two night applications of towlettes with the same percentage of tretinoin and vitamin C) (Figures 9.1, 9.2). This peel is self-neutralizing.

Figure 9.1 Skin tone solution of tretinoin available in Brazil

Figure 9.2 Vi Peel^™ components

The Melanage Peel^™, designed for dark skin types with melasma or PIH, is commercially available as a kit (Figures 9.3 to 9.5). The kit includes a 1% tretinoin solution and a powder formulation of hydroquinone, which is mixed fresh at the time of use with 10% azelaic acid, 10% lactic acid, and 10% phytic acid. The peel is applied as a mask in the clinic and removed by the patient at home. Dermatologists can also make up to a 14% hydroquinone peel, which is left for up to 8 hours on the skin. The key features of this peel are that it is weakly acidic, noncorrosive, minimally inflammatory, and causes no protein precipitation. This peel can be performed once yearly, and can be followed by a series of 3 to 4 minipeels during the year. The kit also includes a ready-to-mix bleaching cream consisting of a 4% hydroquinone with 0.025% tretinoin or a percentage chosen by the physician to be applied nightly for 2 months.

Figure 9.3 Application of the skin tone tretinoin solution

Figure 9.4 Melanage^™ Peel components

Figure 9.5 Application of the skin tone tretinoin solution

Phenol Peels

These include modified phenol peels where the percentage of croton oil directly affects the penetration and thus the cutaneous and cardiac toxicity of the phenol component. It includes Hetter’s range of phenol formulas like the ‘all around’ (35% phenol, 0.1–0.4% croton oil), Delasco’s Stone 100 (60% phenol, 0.2% croton oil) and the patented Exoderm^™. Depigmentation is no longer seen with these phenol peels; rather a pseudo-hypopigmentation develops over the following 1–2 years, which has the cosmetically acceptable appearance of the patient’s non-sun-exposed skin. Cardiac arrhythmias have not been a medical issue provided proper precautions are taken: heart rate and pain are controlled by nerve blocks which do not contain epinephrine in, pulse oximetry monitoring with the pO₂ is maintained above 90%, appropriate IV hydration, and the peeling solution is applied slowly over 60 minutes.

Preoperative Care

Preparation of the skin before peel is very important to improve results and reduce the risk of complications. The darker the skin, the longer the duration of the preconditioning should be prior to the chemical peel. A minimum period of 2 weeks is recommended to prepare the skin.

Skin preparation with bleaching agents such as AHA, 4% hydroquinone, azelaic acid or kojic acid formulations, and early reintroduction of these products in the immediate postpeel period are crucial to prevent PIH in dark phenotypes. Retinoids such as tretinoin, tazarotene and retinol are often used to treat hyperpigmentation or photodamage in darker skin types. However, it is recommended that these be discontinued 1–2 weeks prior to peeling to avoid postpeel complications in darker skinned patients. As retinoids increase epidermal turnover, they can increase the penetration and depth of the peeling agents. This may be a desired effect in skin types I–III. However, in darker skinned patients, the increase in the depth of the peel may result in excessive erythema, crusting, desquamation, and PIH. Bleaching agents, which do not contain retinoids (lower strength AHA, polyhydroxy acids, and beta-hydroxy acids) are less aggressive agents and can be continued up to 1 or 2 days prior to peeling. Sun exposure should be avoided for at least 2 months before and after treatment. Sunscreens must be always used.

Procedure for Superficial Peels

To minimize the adverse effects of chemical peeling in the skin of color, the dermatologist should perform staged peels, at 2–4 week intervals for superficial peelings. Also, the initial peel should be performed with the lowest concentration of the peeling agent to assess the patient’s sensitivity and reactivity. Photographic documentation prior to the peel is mandatory.

Skin preparation immediately before peeling is the same for all type skin patients, even darker skin group. The face is cleaned with soap and water. The hair is pulled back with a hair band or cap. The patient lies down with head elevated to 45° with the eyes closed to avoid accidental spillage of the agent. Using gauze pads, the skin is cleaned again with alcohol and then degreased with acetone.

Anesthesia is not required for superficial chemical peelings. Mild tranquilizers can be used in very anxious patient in medium-depth and deep peelings.

The label on the bottle must be precisely checked before applying the peel.

Sensitive areas like the inner canthus of the eyes and nasolabial folds can be protected with Vaseline. The peeling agent is then applied with a gauze or cotton-tipped applicator.

When performing glycolic acid peeling, the agent should be neutralized after the predetermined duration of time (usually 2–3 minutes). However, if erythema or epidermolysis occurs, the peel must be neutralized immediately, with neutralizing lotions or 10–15% bicarbonate solutions followed by rinsing off with water.

While TCA peels are self-neutralizing, the stinging sensation on the skin can be calmed with cold water application.

When the salicylic acid peeling is performed, it crystallizes and forms a pseudo-frost. This precipitate can be washed with water after 3–10 minutes.

Jessner’s solution is applied with 1–3 coats, and the endpoint is erythema and/or a mild frost. No neutralization is required.

Tretinoin peels can be left on for 4–12 hours depending on skin sensitivity. Water can be used to rinse off the yellow-hued tretinoin.

Postoperative Care

The objective of the postoperative care is to minimize complications and ensure early recovery. This is most important in dark skin patients because they have a greater risk of pigmentary alterations. Thus, maintenance therapy after a peel is important to achieve the best results. This usually involves the same agents of the preoperative care, administered after skin reepithelialization, with broad-spectrum sunscreens used as soon as possible. Sun exposure must be avoided for at least 8 weeks after the peel to minimize the risk of PIH. In the postpeel period, edema, erythema and desquamation can occur and last 1–5 days in superficial peelings. The physician should advise the patient to avoid peeling or scratching the skin since scarring or dyschromia can result.

The healing process after a chemical peel must be as rapid as possible so as to avoid infections. While uncommon, infections may deepen the wounds irregularly, converting an anticipated superficial peel into a deep peel and increasing the chance of scarring. If excessive crusting occurs, topical and/or oral antibiotics should be prescribed to treat presumed bacterial infection.

PIH

This adverse effect occurs frequently in patients with dark complexions. It may develop very soon after the peel or months later. Skin priming using a bleaching agent before the superficial and medium-depth peels followed by early reintroduction of this preparation helps to minimize this untoward effect. It can be persistent and very difficult to treat, especially in darker skintypes. Treatments include: sunscreens, topical corticosteroids, tretinoin, AHA, kojic acid, azelaic acid or hydroquinone. Sun avoidance is very important during the treatment. Light peels that do not create as much inflammation, i.e., salicylic acid 30% solution or tretinoin peel, may be used to treat PIH if needed. Short-term application (under 12 weeks) of class VI steroid creams like fluocinolone 0.01% BID can be extremely helpful in treating early PIH in skin that is still sensitive after the peel and cannot tolerate retinoids or hydroquinones.

Hypopigmentation

Areas of permanent hypopigmentation can frequently result due to destruction of melanocytes in the hair follicles following reticular peels. Most patients with this complication need to use cosmetics to camouflage the hypopigmented areas. It can be very persistent and difficult to treat.

Milia

This can appear in up to 20% of patients after chemical peels, usually 8–16 weeks after the procedure. It can be treated with electrosurgery or extraction.

Acneiform Eruption

This consequence is fairly common after chemical peels and usually appears immediately after reepithelialization. Its etiology is multifactorial and is related to either exacerbation of previously existing acne or occlusion resulting from emollients being applied to healing skin. Treatment is straightforward with oral antibiotics used to treat acne such as tetracycline or minocycline, and others.

Infections

While infection is rare after any type of peel, it tends to result more frequently after medium and deep peels. It is not the infection per se that is problematic, but rather the associated scarring that can ensue. If bacterial, fungal or viral infection is suspected, empiric therapy should be started after a culture is taken. Infections can be bacterial (most commonly staphylococci and streptococci), viral (herpes simplex) and fungal (Candida). Patients with positive history of herpes simplex infection should be treated prophylactically with acyclovir or valacyclovir until full reepithelialization is achieved.

Scarring

This adverse effect remains the most dreadful complication of chemical peels. It it is rare in superficial peels. However, there is an increased risk of scarring in patients with a history of poor healing and keloid formation, patients who have been previously treated with isotretinoin especially within the previous year, patients undergoing deep peels or a second peel too soon after a previous peel or extensive facial surgery, and in patients who develop an infection after the peel. Most scars result from other complications such as infection or premature peeling. Delayed healing and persistent erythema are important alarming signs of impending scar formation. Hence, careful monitoring of the patient in the postpeel phase is very important for early detection and treatment of such complications. Also, proper skin preparation before the peel and appropriate selection of peeling agent can help to prevent this potential complication. Hypertrophic scars and keloids can be treated with potent corticosteroids topically or intralesionally. Resistant scars may be treated with dermabrasion or pulsed dye laser followed by compressive silicone sheeting therapy.

Toxicity

Although rare, toxicities can occur with resorcinol, salicylic acid and phenol peels.

Premature Peeling

Premature peeling increases the risks of infection, persistent erythema, PIH, and scarring of the underlying skin. It may occur accidentally or may be the result of picking at the peeling skin. If nonepithelialized tissue is exposed, patients should receive a course of oral antibiotics until reepithelialization occurs. The use of topical antibiotics and hydrocolloid dressings should be included in the management. Topical steroid cream can be used if the newly epithelialized skin appears bright red after premature peeling.

Persistent Erythema

Patches of erythema persisting for more than 3 weeks is indicative of early hypertrophic scar formation and should be treated with potent topical corticosteroid therapy.