Guide overview
Start with the shared principles
AHA, BHA and PHA are useful discovery classes, not standardized formulas. Identify exact Lactic Acid, Mandelic Acid, Glycolic Acid, Salicylic Acid or Gluconolactone before choosing timing, frequency or a pairing.
Separate class from identity
AHA includes different materials such as Glycolic, Lactic and Mandelic Acid. BHA commonly points to Salicylic Acid in skincare discovery but remains broader than an exact checker alias. PHA can include Gluconolactone and other materials. A front-label abbreviation does not replace the complete INCI.
What matters beyond percentage
pH, solvent, contact time, rinse-off or leave-on use, other acids and weekly frequency all affect irritation. The same percentage cannot be compared directly across different materials, and professional-peel numbers are not home-use instructions.
Beginners should choose one
Start one home acid one evening weekly and keep several basic moisturizing evenings after it. Consider a second non-consecutive evening only after two to four stable weeks. A change in acid identity is a new product introduction.
Mixed-acid and Pair boundaries
Treat a finished mixed-acid product as one formula; it does not validate do-it-yourself reconstruction. Studies comparing separate professional peels are not combination evidence. Alternate-day Pair guidance manages cumulative irritation rather than claiming toxicity or cancellation.
Sun protection and stop signals
FDA guidance warns that AHA use may increase sun sensitivity. Keep broad-spectrum sunscreen consistent. Stop acids for persistent burning, swelling, cracking, widespread peeling or an expanding rash, and delay use on sunburned or broken skin.
References
Sources
- Peer reviewedGlycolic acid peel therapy – a current review
Clinical, Cosmetic and Investigational Dermatology
- Professional organizationSafety Assessment of Glycolactones as Used in Cosmetics
Cosmetic Ingredient Review