The pH Revolution

Skin has its own pH, the acid mantle, and it sits between 4.5 and 5.5 in healthy adults. That acidity isn't decorative. It's antimicrobial, it activates the enzymes that build the barrier, and it gates the absorption of every active you apply.

Why product pH matters

Many active ingredients are pH-dependent:

• ·L-ascorbic acid (vitamin C) is only stable and active below pH ~3.5. Above pH 4, it oxidizes and loses efficacy.
• ·AHAs (glycolic, lactic) work in the 3.0–4.0 range. Higher pH = lower activity.
• ·Salicylic acid (BHA) is most lipophilic and effective at pH 3.0–4.0.
• ·Niacinamide works across pH 4–7 but degrades into nicotinic acid (which can flush) at low pH if combined with strong acids in the same step.

The bar soap problem

Traditional bar soaps run at pH 9–10. A single wash spikes skin pH for up to an hour and disrupts the lipids that maintain the acid mantle. Repeated daily over years, this is one of the largest drivers of "chronic sensitive skin" in middle-aged consumers who never identified the cause.

What to look for

A good cleanser should be pH 4.5–6.5. Anything that says "syndet" or "synthetic detergent" is engineered to that range. If a brand won't tell you the pH, assume it's not optimized.

The recovery curve

Even when you wash with a high-pH product, your skin restores its own pH within roughly 60 minutes. Once is fine. Twice daily, every day, over years, that's the problem.