AHAs, BHAs, and PHAs – Uses and Contraindications

AHAs, BHAs, and PHAs are often spoken about as interchangeable exfoliating acids, yet they behave very differently on the skin and carry very different risks when misused. This educational resource unpacks what these acid types actually do, how they interact with the stratum corneum, and why choosing the wrong acid or using it incorrectly can quietly compromise barrier health over time.

Inside, you’ll explore how molecular size and solubility influence penetration, why some acids increase photosensitivity while others are better tolerated, and how exfoliation differs between the skin surface and the follicular unit. Common myths around “gentle acids,” pore penetration, and skin thinning are addressed with clear, science-based explanations.

This document also dives into when acids should not be used, how cumulative exfoliation occurs even at low concentrations, and why more exfoliation does not equal better results. Rather than focusing on trends or marketing language, it provides the context needed to make informed formulation, product selection, and education decisions.

Designed for formulators, brand owners, and serious skincare learners, this resource offers the kind of clarity that changes how you approach chemical exfoliation altogether.