Alpha-hydroxy Acid Peels

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4 Alpha-hydroxy Acid Peels

Introduction

Alpha-hydroxy acid (AHA) peels are popular in dermatologic practices for their ability to deliver both an aesthetic and therapeutic benefit to the skin with a quick recovery time. AHA peels have earned their nickname as ‘lunchtime peels’ because there is minimal apparent disfigurement immediately post peel. Additionally, because their effect is largely at the stratum corneum through to the basilar layer of the epidermis, AHA peels are classified as superficial chemical peels. Due to their role as superficial peeling agents, AHA peels can be used to treat all skin types and various disorders of keratinization. To date, glycolic acid is the preferred AHA in use as a single peeling agent. Another AHA, lactic acid, has been used largely as a peeling agent combined with other reagents such as salicylic acid (euphemistically referred to as a beta-hydroxy acid) and will be discussed in the Jessner’s peel section of this book. While there are other emerging alpha-hydroxy acids, such as mandelic and citric acids that can either be used singly or in combination as peeling agents, there are no clinical studies at this time to merit further discussion.

This chapter will review the use of AHA peels––in particular, glycolic acid peels (GAP)––in the treatment of the signs of photoaging, acne, melasma, lentigines and seborrheic keratosis, keratosis pilaris, and warts. Furthermore, GAP can be used in combination with fluorouracil to treat pre skin cancer conditions, such as actinic keratosis and actinic cheilitis.

Glycolic Acid Peels

Glycolic acid has the smallest molecular weight of all AHAs and therefore is easily able to traverse the skin, depending on its vehicle, formulation, pH, site of application, and the condition of the skin to which it is being applied. When choosing glycolic acid as a peeling agent, it is then important to understand that the vehicle, formulation, and pH are essential to the success of the peel.

Choosing a glycolic acid peel formulation

Glycolic acid in its raw form is a crystal which is then dissolved into a vehicle. The diluent’s vehicle can impact the peel’s efficacy and is an important part of the practical clinical consideration in peel selection. For example, glycolic acid peels that are formulated in a gel based vehicle may have a partition coefficient that slows the delivery of the active agent. The effect would be to make the active peel ingredient less bioavailable to the skin, thereby slowing the process and rendering it less attractive as an office-based procedure in which a quick response time is needed. However, AHA peels formulated in a gel base may be well received by patients with sensitive skin or rosacea who are desirous of the peel and are only interested in mild exfoliation and no irritation. On the other hand, aqueous based peel solutions containing glycolic acid allow ready passage through the stratum corneum and are generally favored in those wanting a quick response with a greater degree of desquamation post peel.

Glycolic acid peels are now available in a variety of delivery systems that are classified as follows:

A free glycolic acid solution refers to a non-neutralized solution of glycolic acid. The glycolic acid then exists in an acidic pH ranging from 0.6 (for a 70% glycolic acid solution) to 1.7 (for a 20% glycolic acid) or 7.0 to 20% glycolic acid in an aqueous vehicle. The free glycolic acid has greater bioavailability and reactivity when applied to the skin which is manifested by erythema. Epidermolysis can result if there is any disturbance in the skin barrier function prior to the peel application.

A partially neutralized glycolic acid peel formulation refers to the combination of the acid with a base; for example, with ammonium hydroxide to yield the salt ammonium glycolate. The pH of this solution is then increased (mean pH is 3.8).

A buffered glycolic acid peel formulation refers to a solution that resists pH changes on addition of acids or bases. When there are equal molar concentrations of glycolic acid and sodium glycolate, the glycolic acid peel solution is then stabilized against the addition of stronger acids in the pH range of 2.8 to 4.8. The role of buffered glycolic acid peels does not appear to offer any practical benefit in its sole use as a peeling agent in the office setting. Marketing tactics have blurred the science and have promoted the concept of buffered solutions to really denote partially neutralized solutions of glycolic acid.

Esterified glycolic acid peel solutions refer to a solution forming a glycol-citrate. This occurs when an ester bond forms between the carboxyl group of glycolic acid and the hydroxyl group of citric acid. The stability of the created dimer of glycolyl citrate or citryl glycolate is questioned. The marketing claims attributed to this admixture of AHAs are that there is less skin irritation; however, this needs further substantiation.

Indications and Considerations in Performing a Glycolic Acid Peel

A pre peel consultation is always necessary to ensure that both physician and patient have communicated a realistic expectation about the risks and benefits of a glycolic acid peel. The ideal patient is one who is looking to freshen their skin’s appearance. Improvement of fine lines, sallow complexions with uneven skin tone, dyspigmentation, lentigines, ephilides, and roughly textured skin types can be achieved with this peel. It is imperative that the physician counsel the patient that these improvements can be achieved only after a series of peels are undertaken in a consistent time frame, such as monthly sessions, until the goals are met. In general, most patients can expect improvement in about six sessions but the actual number of treatments needed will vary depending on the underlying skin conditions being addressed. Deeper lines, wrinkles, and grooves will not be improved with these peels and other modalities should be employed.

Glycolic acid peels are used as adjunctive treatments in conditions such as acne, postinflammatory hyperpigmentation usually resulting from acne, shallow acne scars, papulopustular rosacea, melasma, seborrheic and actinic keratoses, keratosis pilaris, and some warts resistant to conventional treatments.

The glycolic acid peel patient is generally one who is interested in minimal recovery time and no interruption of work or social obligations. It is important to discern from the patient if they are willing to go through the series to obtain the results desired. If the patient prefers a one time treatment and is willing to undergo a lengthier recovery period then it is best to advise them regarding medium or deeper depth chemical peels or laser resurfacing.

It is also important to understand where the patient seeks improvement. While the face is generally the most coveted site, many patients seek improvement in other areas of the body namely the chest and neck, back, dorsal hands, arms and legs. These cosmetic units can be treated with glycolic acid peels but it should be noted that the neck is the most sensitive. It is therefore recommended that a lesser concentration of the glycolic acid be applied to the neck first before attempting higher levels. In contrast, the chest, back, arms, legs and hands seem to tolerate higher concentrations of glycolic acid peels more favorably.

Unlike some other chemical peeling agents that pose a risk of hyper or hypopigmentation to darker skin types, glycolic acid peels can be used on all Fitzpatrick skin types I through VI, male or female, teens to adults. The most sensitive skin types appear to tolerate glycolic acid peels in lower concentrations (20–35%) only. Patients with rosacea and atopic dermatitis and patients of Asian descent appear to fall into this category.

Reviewing the history and examination

At the time of the prepeel consultation, the physician should obtain a detailed medical and skin history.

Any prior history of viral infections, such as chronic or recurrent herpes simplex, active dermatoses of the atopic, seborrheic or eczematous types, and medications such as topical or oral retinoids, must be reviewed. Those patients with a history of recurrent herpes infection should be treated prophylactically with oral antiviral agents, preferably Valtrex (valacyclovir), on the morning of the peel and continued for a routine course of therapy. If the patient presents on the morning of the peel with active herpetic infection in the areas to be treated, it is best to postpone the peel until complete resolution has occurred.

Oral and topical retinoids may cause disruption of the stratum corneum and thereby enhance the depth of penetration of the glycolic acid peel. Therefore, patients on oral isotretinoin or topicals, such as tretinoin, adapalene, or tazarotene, may experience increased reactivity to the glycolic acid peel. It is then recommended that the topical agents be stopped at least 7 days in advance of the peel. Because isotretinoin needs to be a continuous therapy and there are questions concerning delayed healing with this therapy, it is best left to the physician’s expertise when to undertake glycolic acid peels in this setting.

Other medications that may affect peel penetration are topical 5-fluorouracil, such as Efudex or Carac, or immiquimod, such as Aldara. The 5-fluorouracil agents and imiquimod will disrupt actinic keratoses and therefore glycolic acid peels may cause epidermolysis of these treated sites. This reaction is favored since effacement of the actinic lesions is integral in the destruction of these premalignant conditions. However, the patient must be prepared in advance that this reaction will occur and to expect a consequent increased recovery period marked by scabbing and desquamation. In addition, those patients on antiplatelet agents such as warfarin, heparin, aspirin, NSAIDs, and even vitamin E, may experience bleeding and eschar development in these combined treatment sites.

Patients using photosensitizing agents such as oral contraceptives and tetracyclines and their derivatives should be counseled to adhere to postpeel instructions regarding strict sunscreen use and photoprotection.

Patients with a history of atopy, eczema, dry and sensitive skin may favor the partially neutralized formulations or lower concentrations of the free glycolic acid peel, or may not be candidates for any peel at all, depending on the severity of their disorder. In order to determine their potential reactivity to the peel, it is recommended that these skin types in particular (and in my practice anyone undergoing a glycolic acid peel) first have a trial period at home using topical products containing glycolic acid for 2 weeks before the peel. I recommend that the patient be started on an 8 to 10% glycolic acid product initially. Any unusual sensitivity to glycolic acid can thereby be unveiled during this prepeel preparation and the peel then could be forfeited. It is best recommended that patients who have undergone dermabrasion, ablative laser resurfacing or other surgeries, or deeper chemical peeling agents wait at least 6 to 12 months for complete healing to take place before undertaking a glycolic acid peel.

Preparing the Patient for the Glycolic Acid Peel

Once the patient is deemed a good candidate for the peel, a daily home care program of topical AHAs, in particular glycolic acid, should be advised. The topical glycolic acid home care products range from 8% to 20% concentrations. When starting this regimen on a patient who has never used the glycolic acid products, it is best to start at the low concentrations and increase as tolerated. In choosing the vehicle for the patient, it is best to match to the patient’s skin type. Cream formulations are preferred by patients with dry skin, gels by oily skin types and lotions by normal skin types. The product should be started nightly for the first 2 weeks then increased to twice daily as tolerated. This will help to determine if the patient has any unusual sensitivity to the glycolic acid prior to the administration of the peel. Also, the glycolic acid product will help to prepare the skin for the peel by allowing for prepeel desquamation. If the patient has any aversion to the appearance of desquamation or peeling per se, the peel should not be engaged. It is important to note that unusual sensitivity to glycolic acid is rare. The patient should also be apprised of the prepeel instructions found in Box 4.1

Box 4.1

Glycolic acid peel/acne wash preprocedure instructions

Whenever possible, it is best to prepare the patient for the peel by showing photographs of various stages of the peels; for example, immediately after and the days following the peel. It is again important to reiterate to the patient that this peel must be repeated on at least a monthly basis to appreciate the purported benefits. At this time, the patient should be made aware of the need to increase the peel strength at subsequent visits based on their prior acceptability and response. Lastly, the patient must be compliant with the products and follow-up care recommendations.

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