How does salicylic acid destroy abnormal cells, such as those found in warts or acne?

Mechanism of Action: How Salicylic Acid Destroys Abnormal Cells

Salicylic acid destroys abnormal cells primarily by dissolving the intercellular cement substance that holds cells together (desmolytic action), causing exfoliation of the stratum corneum and epidermal cells, while at higher concentrations it acts as a direct irritant that may additionally stimulate host immunity against infected tissue. 1, 2

Primary Cellular Destruction Mechanisms

Desmolytic Action (Not Keratolytic)

• Salicylic acid disrupts cellular junctions between cells rather than breaking down keratin filaments themselves, which is why it's more accurately described as a desmolytic agent rather than a keratolytic agent 3
• The FDA describes this mechanism as "dissolution of intercellular cement substance" that produces desquamation of the horny layer without affecting the viable epidermis qualitatively or quantitatively 1
• This disruption of cell-to-cell adhesion causes abnormal cells (like those in warts or acne comedones) to shed more rapidly 3

Concentration-Dependent Effects

• At lower concentrations (0.5-2%), salicylic acid promotes gentle exfoliation suitable for acne treatment 2
• At moderate concentrations (10-26%), it functions as both an exfoliant and irritant for wart treatment 2
• At high concentrations (40-50%), it becomes a potent irritant that aggressively destroys hyperkeratotic tissue 4, 5

Secondary Immune Stimulation

Inflammatory Response

• The irritant properties of salicylic acid at higher concentrations are postulated to stimulate host immunity, which may be an additional mechanism of action against warts 2
• This immune stimulation helps the body recognize and destroy virus-infected cells in warts, though the evidence suggests this is essential since immunosuppressed patients show poor response to treatment 2

Clinical Application by Condition

For Warts (Viral-Infected Cells)

• The British Association of Dermatologists recommends 15-40% concentrations that work through combined exfoliation and immune stimulation 2, 4
• Lesions should be abraded or pared down before application to enhance penetration into the abnormal tissue 2, 4
• The meta-analysis demonstrates warts treated with salicylic acid are 16 times more likely to clear than placebo, with cure rates of 49% versus 23% 4

For Acne (Comedones and Inflamed Follicles)

• Lower concentrations (0.5-2%) applied 1-3 times daily provide comedolytic effects by disrupting the cellular plugs in follicles 2
• The desmolytic action specifically targets the abnormal keratinization that creates comedones 3

For Corns (Hyperkeratotic Tissue)

• High concentrations (40-50%) in plasters directly destroy the thickened abnormal keratinocytes through aggressive irritation and dissolution 5

Important Caveats

Selectivity Limitations

• Salicylic acid is not truly selective for abnormal cells—it will damage normal skin if applied to surrounding tissue, which is why careful application and paring technique matters 4, 5
• The "selectivity" comes from: (1) thicker abnormal tissue absorbing more product, (2) targeted application technique, and (3) the fact that normal epidermis regenerates while abnormal tissue (like warts) cannot 1

Systemic Absorption Risk

• The FDA notes that salicylic acid is absorbed percutaneously, with peak serum levels occurring within 5 hours, though toxic levels (30-40 mg/100 mL) are rarely reached with proper use 1
• Avoid applying to more than 20% of body surface area to prevent salicylate toxicity 5