AHA, BHA and PHA: designing a sensible exfoliation choice
SESH ACADEMY · INTERMEDIATE SKINCARE
AHA, BHA and PHA: designing a sensible exfoliation choice
Match exfoliant type and contact pattern to concern and tolerance.
Compare the acidic, neutral and alkaline parts of the pH scale. A pH value alone does not determine exfoliation strength or skin compatibility.
Different acids, different considerations
Glycolic and lactic acids are AHAs used for surface exfoliation and texture in suitable formulas. Salicylic acid is a BHA used around clogged pores. PHAs such as gluconolactone have different properties and may be better tolerated in some formulations, but 'gentle' does not mean irritation-proof.
Concentration alone is insufficient
Effects depend on pH, acid identity, concentration, exposure time, rinse-off behavior and the finished formula. Do not compare a short-contact mask directly with an overnight leave-on based solely on percentage. Strong or professional peels carry distinct safety concerns.
Plan around tolerance
Some AHAs can increase sun sensitivity, so follow label warnings and maintain UV protection. Avoid impulsively adding strong acids over existing retinoid therapy or irritated skin. Visible peeling is not the goal.
Find the stratum corneum at the top and cell renewal below. This is thick skin, such as a palm; its clear lucidum layer is absent from facial skin.
Apply this to a realistic case
Case: 2% leave-on versus 10% rinse-off
A learner ranks a 10% wash-off peel above a 2% leave-on product solely by percentages, ignoring acid identity, pH and contact time.
Reasoned next step: Evaluate formula, contact time and tolerance rather than raw percentages.
The pitfall to avoid
Using more visible peeling as a success metric.
Related Ingredient Dictionary entries
Related SESH product examples
These illustrate product roles and ingredient lists, not proof that the products clinically treat every condition described.
Evidence and further reading
Educational information for understanding decisions. It does not diagnose or replace medical advice.
