What is the difference between AHA and BHA?
AHAs like glycolic and lactic acid are water-soluble and work on the skin's surface to brighten and smooth, while BHA like salicylic acid is oil-soluble and gets into pores. In Korean skincare both are used sparingly, a few times weekly, always with daily sun protection.
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AHAs suit dullness and surface texture; BHA suits oily, congested, blemish-prone skin.
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What is the difference between essence and serum?
In Korean skincare, essence is typically a thinner, hydration-focused layer that preps skin, while serum is more concentrated with targeted actives like vitamin C or niacinamide. Essence usually comes first; serum follows. The line between them blurs, and not every routine needs both.
What is the difference between essence, serum and ampoule?
Essence is the lightest and most hydration-focused, serum is more concentrated and targeted, and ampoule is the most concentrated of the three. The boundaries are marketing convention, not regulated definitions.
What is BHA and what does it do?
BHA, usually salicylic acid, is an oil-soluble exfoliant that can penetrate pores to dissolve oil and dead skin, helping refine the look of texture and blemish-prone skin. In Korean routines it's used a few times weekly, with sunscreen by day, to avoid over-exfoliating.
✍️ Written & reviewed by the KoreaPlus Editorial team — dermatologist-informed, cosmetic-science researched & source-cited. Last reviewed: 2026-08-23.
General educational information using cosmetic structure-function wording — not medical advice. Always patch-test new actives. © KoreaPlus.