Aesthetic Dermatology MCQ - Phenol Peel

A 50-year-old woman with deep perioral rhytides undergoes a chemical peel that penetrates the reticular dermis. The peeling agent used is known for causing direct cytotoxic injury to keratinocytes and fibroblasts rather than protein coagulation. Which of the following agents acts primarily by toxic action?

A. Glycolic acid
B. Trichloroacetic acid
C. Salicylic acid
D. Phenol
E. Mandelic acid

Correct Answer:
D. Phenol

Explanation:
Peeling agents can act by keratolysis, metabolic action, caustic protein coagulation, or toxic cellular injury.

• Phenol (carbolic acid) is the prototype peel with toxic action.

• It penetrates deeply into the dermis and causes direct cytotoxic injury to keratinocytes and fibroblasts, leading to destruction of epidermis and part of the dermis, followed by re-epithelialization and dermal remodeling.

• Because of its systemic absorption potential, phenol peels can cause cardiac arrhythmias, renal and hepatic toxicity — careful monitoring and patient selection are required.

Other options:

• A. Glycolic acid: Keratolytic (AHA) → breaks corneocyte cohesion.

• B. Trichloroacetic acid: Caustic (protein coagulation) with frosting.

• C. Salicylic acid: Metabolic action (sebostatic, comedolytic).

• E. Mandelic acid: AHA — keratolytic, used in sensitive skin.

Key Point:
Phenol peel is the classic example of a peel with toxic action, capable of reaching the reticular dermis and used for deep wrinkles and severe photodamage — but with significant systemic risks.