pH, free acid and interpreting labels
A lower pH does not automatically mean a better exfoliant. Learn the role of acidity, free-acid fraction, concentration, buffering and skin tolerance without being asked to mix acids yourself.
pH is not the same as acid percentage
pH measures hydrogen-ion activity on a logarithmic scale in a given system; 5% glycolic acid describes an ingredient amount. In simple acid systems, pH and pKa influence the undissociated acid fraction, which may affect partitioning and activity. The complete formula, buffering and use directions matter. Comparing just two numbers across products omits critical context.
pH, free acid and interpreting labels — a published visual reference for the topic, not SESH product-test data.
Open full-size image ↗Why two products may feel different
Exfoliating acid concentration, free-acid availability, contact duration, supporting moisturisers and individual barrier status all contribute to tolerability. A formula marketed as 'gentle because pH 5' is not proven non-irritating for everyone. Likewise, a slightly lower pH product need not deliver better outcomes in a controlled trial.
Avoid misusing a generic diagram
The public-domain pH chart illustrates the general scale using common substances, not the measured pH or free-acid content of any SESH product. A supplier should provide relevant finished-formula testing. At-home strip readings on complex skincare products can be misleading and cannot establish safety or efficacy.
Clinical outcomes still win
For claims about roughness, acne marks or pore appearance, seek controlled studies measuring those endpoints and adverse reactions. Someone with stinging or compromised skin should not raise frequency simply because a chart calls a solution 'mild'. Product instructions and individual tolerance take priority.
Compare the acidic, neutral and alkaline parts of the pH scale. A pH value alone does not determine exfoliation strength or skin compatibility.
Practice lab
Two exfoliants both claim 8% AHA, one at pH 3.5 and one at 4.1. An influencer says the first is twice as effective and safe for daily use. How should you respond?
Evidence-bounded answer
pH difference alone does not quantify efficacy or safety, and the acid identity, formulation and exposure matter. Do not invent a twofold effect or recommend daily escalation without relevant evidence.
References
Related SESH learning
Links for learning, not evidence of clinical efficacy or product superiority.
