Salicyclic Acid (SA)

  • Also known as 2-hydroxybenzoic acid
  • Classified either as a β-hydroxy acid or as a phenolic aromatic acid
  • 0.5-40%  
  • Lotion, ointment, gel, foam, solution, shampoo, plaster

  • Keratolytic & desmolytic: decrease corneocyte adhesion & loosening / detachment of corneocytes (considered more as a desmolytic agent i.e. disruption of desmosomes with no lysis of keratin filaments)
  • Photoprotection: Due to its benzene ring, changes UV radiation into longer-wavelength radiation, which is then emitted as heat
  • Salicylates absorb UVB 300-310 nm
  • Anti-inflammatory with 0.5% and 5%: Similar to acetylsalicylic acid (inhibition of prostaglandin)

  1. Hyperkeratotic diseases:
    • Calluses / corns (10-40%)
    • Hyperkeratosis (2-10%)
    • Ichthyosis
    • Keratoderma
  2. Infections:
    • Verruca, Molluscum (10-40%)
    • Dermatophyte
  3. Papulosquamous:
    • Psoriasis
  4. Cosmetic:
    • Hyperpigmentation
    • Rejuvenation / peeling (20-30%) / Jessner’s solution
  5. Dermatitis:
    • Seborrheic dermatitis
  6. Other:
    • actinic keratosis (10% salicylic acid + 5-Fluorouracil)
    • Acne (0.5-2% = comedolytic)
    • Photoprotection (octyl salicylate & homomenthyl salicylate)
    • Pruritus
    • Hyperhidrosis (2% salicylic acid with 15% Aluminum chloride hexahydrate: decreased irritation)

  • Pregnancy Category C

Irritation, burning, erosions, peeling

  • Salicylism secondary to systemic absorption –rare (> 35mg/dL):

Typically, within 2-3 days after treatment; nausea, vomiting, confusion, dizziness, hyperventilation, metabolic acidosis (children), hypo-glycemia, coma & death

  • Tinnitus = early sign of salicylate toxicity
  • Hypoglycemia 2nd to systemic absorption
  • Allergic contact dermatitis (uncommon)

  • Salicylates = converted to salicylic acid
  • Lipid soluble (unlike α-hydroxy acids): interactions with lipids around keratinocytes & hair follicles
  • Effect limited superficial epidermis
  • Readily absorbed on skin: 
    • Increased absorption in hydrophilic ointment, tape stripping or occlusion
  • Indications as per % of salicylic acid:
    • 0,5-2% = comedolytic (acne)
    • 2-10% = hyperkeratosis dermatoses
    • 10-40% = calluses; wart; increase penetration of other topical treatment
    • 20-30% = chemical peels