Aesthetic Dermatology MCQ - Choosing a peeling agent

A 25-year-old woman with Fitzpatrick skin type III and active facial acne vulgaris presents for a chemical peel. She has numerous open and closed comedones, as well as inflammatory papules. Which of the following peeling agents is most appropriate for its comedolytic, anti-inflammatory, and keratolytic properties, and is particularly safe in darker skin types due to its minimal risk of hyperpigmentation?

A) Salicylic acid 20-30%
B) Trichloroacetic acid (TCA) 25%
C) Glycolic acid 50-70%
D) Jessner's solution
E) Pyruvic acid 50%

Correct Answer: A) Salicylic acid 20-30%

Explanation

This patient has active acne vulgaris with comedones and inflammatory lesions. The choice of peeling agent must target these specific concerns while minimizing the risk of post-inflammatory hyperpigmentation (PIH), which is a significant concern in Fitzpatrick skin type III.

Why Salicylic Acid is the Best Choice:

• Mechanism of Action: Salicylic acid is a beta-hydroxy acid (BHA) with excellent keratolytic and comedolytic properties. It is lipid-soluble, allowing it to penetrate into sebaceous follicles and dissolve comedones.

• Anti-inflammatory: It has inherent anti-inflammatory effects, making it ideal for inflammatory acne.

• Safety in Darker Skin: Salicylic acid peels are superficial and cause epidermal exfoliation without significant inflammation, drastically reducing the risk of PIH compared to other agents. This makes them exceptionally safe for Fitzpatrick skin types III-VI.

• Clinical Use: 20-30% concentrations are used for acne. It produces a faint whitish "pseudo-frost" due to precipitation of the acid.

Why Not the Other Options?

• (B) Trichloroacetic acid (TCA) 25%: A medium-depth peel that can improve acne scarring but is too aggressive for active inflammatory acne. It carries a higher risk of PIH and scarring in darker skin.

• (C) Glycolic acid 50-70%: An alpha-hydroxy acid (AHA) that is water-soluble and effective for superficial peeling and mild acne. However, it can cause more irritation and has a higher risk of PIH than salicylic acid in darker skin.

• (D) Jessner's solution: A combination of resorcinol, salicylic acid, lactic acid, and ethanol. It is effective for acne but contains resorcinol, which can cause allergic contact dermatitis and is less predictable than salicylic acid alone. The multiple ingredients increase irritation potential.

• (E) Pyruvic acid 50%: An alpha-keto acid with keratolytic properties. It is used for acne but is highly irritating and can cause burning and PIH. It is not first-line.

Peel Procedure:

• Application: Even application with a brush or sponge; a slight tingling is normal.

• Endpoint: A faint frost indicates penetration.

• Post-peel: No neutralization is required as salicylic acid is self-limiting.

Postoperative Care:

• Sun protection with broad-spectrum SPF 50+ is mandatory.

• Avoid picking or scrubbing the skin.

Prognosis:
Excellent for comedonal and inflammatory acne. A series of 4-6 peels every 2-4 weeks is typically performed.

Note: Salicylic acid peels are a cornerstone in the treatment of acne in all skin types, especially darker skin, due to their efficacy and safety profile. They should be part of a comprehensive acne management plan that includes topical retinoids and benzoyl peroxide. Always assess the patient's skin sensitivity and history of PIH before proceeding.