The Lipophilic Chemistry of Salicylic Acid
Water-soluble acids (like AHAs glycolic and lactic) bounce off the natural lipid plug of a pore like water off duck feathers. They work exclusively on surface dead skin cells.
Salicylic acid possesses a lipophilic (fat-loving) benzene ring. It dissolves directly into the sebum matrix, traveling down the infundibulum of the hair follicle. Once inside, it dissolves the desmosomes holding compacted dead skin cells together, liquifies oxidized sebum plugs, and exerts a natural aspirin-like anti-inflammatory action that rapidly shrinks red blemishes.
The Purging Phase vs. Chemical Irritation
Because BHA accelerates cellular turnover inside clogged follicles, micro-comedones that were already forming under the skin will surface faster over the first 2 to 4 weeks. This is 'purging' and is a healthy sign that pores are clearing.
If you experience burning, widespread red itching, or peeling on areas where you never break out, that is barrier damage from over-use. Cut back to once a week and restore your barrier with ceramides.