The Korean Regulatory Background: The 0.5% BHA Cap
In South Korea, the Ministry of Food and Drug Safety (MFDS) strictly restricts over-the-counter leave-on cosmetics to a maximum of 0.5% pure Salicylic Acid due to concerns over barrier irritation and systemic salicylate absorption.
Because 0.5% BHA is insufficient to clear stubborn closed comedones, Korean cosmetic chemists formulated around the restriction by synthesizing Betaine Salicylate: an equimolar compound formed by combining pure salicylic acid with betaine (trimethylglycine).
Under Korean cosmetic law, Betaine Salicylate is classified as a distinct cosmetic raw material, permitting formulations with up to 4% concentration.
Molar Equivalence & Penetration Dynamics
Salicylic acid has a molecular weight of 138.12 Da, while Betaine has a molecular weight of 117.15 Da. In 4% Betaine Salicylate, approximately 2% by weight represents active salicylic acid, while the remaining 2% represents hydrating betaine.
The betaine moiety acts as an intrinsic osmolyte buffer, preventing the rapid drop in cutaneous surface pH that triggers sensory burning with Western 2% BHA.
The result: 4% Betaine Salicylate delivers equivalent comedolytic pore refinement to 2% Salicylic Acid with less barrier flaking and irritation.
LHA (Capryloyl Salicylic Acid): Micro-Exfoliation at pH 5.5
Capryloyl Salicylic Acid (LHA), patented by L'Oreal, is a salicylic acid derivative conjugated with an 8-carbon lipophilic fatty acid chain (octanoyl).
Because of this fatty lipid tail, LHA is dramatically more lipophilic than pure salicylic acid. It penetrates into the stratum corneum with high spatial precision, exfoliating corneocytes individual cell-by-cell rather than causing sheet-like peeling.
Most remarkably, LHA exfoliates efficiently at a physiological pH of 5.5, eliminating the need for the aggressive low-pH vehicles (pH 3.0 to 3.8) required by classic BHA.
Takeaway: Use Western 2% Salicylic Acid for rapid, aggressive blackhead and cyst decongestion. Use Korean 4% Betaine Salicylate for gentle daily maintenance. Use LHA for rosacea-prone or highly sensitized skin that requires cell-by-cell exfoliation at skin-friendly pH.