The three groups
AHAs are water-soluble acids often used for dullness, uneven texture and surface pigmentation. BHAs are oil-soluble; salicylic acid is commonly chosen for oily, congested or blemish-prone skin. PHAs have larger molecules and are often positioned as a gentler surface-exfoliating option.
The label AHA, BHA or PHA does not predict the whole experience. Concentration, pH, vehicle, contact time and the rest of the routine all affect tolerability.
How to choose
Choose by the main concern and skin tolerance, not by trends. Dry or sensitive skin usually benefits from a conservative approach; oily skin does not need the strongest acid available. A leave-on toner, serum and peel may all be exfoliants even when the product names sound different.
Start with one exfoliating product and use it exactly as directed. Do not stack an acid toner, peel and scrub on the same day.
Signs of over-exfoliation
Burning, persistent redness, tightness, unusual shine with sensitivity and flaking suggest that the routine may be too aggressive. Pause exfoliants, simplify to gentle cleansing and moisturizer, and use sunscreen.
Seek professional advice if symptoms are severe or persistent. Acids do not replace treatment for significant acne, dermatitis or suspicious pigmentation.
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Sources
This article provides general information and does not replace an individual consultation with a dermatologist.