Cleanser pH : How Much Does It Really Affect Your Skin?

How Much Does the pH of a Cleanser Really Matter?

The pH of cleansing product is often discussed in skincare science and product formulation.

You often hear that “weakly acidic pH is best for the skin.”

But does that mean weakly alkaline cleansers should be avoided altogether?

In a previous article, it was explained why the pH of the healthy skin surface (often referred to as “skin pH”) is maintained at a weakly acidic level, and how— from a formulation perspective — many weakly acidic cleansers are designed to minimize changes in skin pH during and after washing.

For clarity, the term “skin pH” in this article refers to the pH of the skin surface.

At the same time, many cleansers — including traditional soaps — are weakly alkaline.

So is being weakly alkaline, in itself, a problem?

What Happens to Skin pH After Washing?

First, it is important to note that the act of washing itself temporarily raises the skin’s pH.

In one study conducted under controlled cleansing conditions¹, changes in skin pH before and after washing were compared using:

• Soap (the exact pH was not specified in the study, but typical soaps range between pH 9 and 11),
• Tap water (approximately pH 8), and
• A shower gel (pH 6).

The graph below is a reconstructed version based on estimated values from the original figure, created to illustrate the general trend.

Figure 1 Reconstructed from the original figure published by Lambers et al.¹ (author’s adaptation based on estimated values)

Under all conditions, skin pH increased immediately after washing, then gradually returned to its original level over time.

In other words, while cleansing causes a temporary rise in skin pH, the skin has built-in mechanisms that help restore it.

The Relationship Between Product pH and Changes in Skin pH

Here, “product pH” refers to the pH of the cleanser itself as used in the study.

A review paper summarising multiple studies reports that both the degree of change in skin pH after washing and the time required for recovery appear to be related, to some extent, to the pH of the cleansing product used².

It is important to note that this review summarised existing studies and did not perform a new statistical re-analysis.

According to the review, under repeated washing conditions:

• Range of skin pH change after cleansing: 0.0 to +3.0 units
• Recovery time: 45 minutes to 8 hours (up to 12 hours in some cases)

An increase of up to around 3 pH units has been reported under experimental conditions. This is not insignificant.

This means that skin which is normally weakly acidic could temporarily rise to around neutral or even higher levels.

However, such changes are not permanent. The skin has regulatory mechanisms that help return it to its original state.

The extent of pH change and the speed of recovery may vary depending on product pH and testing conditions.

That said, these findings were obtained under repeated washing conditions in controlled experimental settings, and may not fully reflect everyday use.

It’s Not Determined by Product pH Alone

There are also reports suggesting that changes in skin pH are not determined solely by product pH³.

In one study, cleansers with identical formulations but different pH levels (4.5 vs 7) were compared under the same conditions². No clear difference in skin pH change was observed.

However, when cleansers had the same pH (pH 4.5) but slightly different surfactant compositions, significant differences in post-wash skin pH were detected.

These findings suggest that changes in skin pH after washing may be influenced not only by product pH, but also by formulation composition.

In short, pH is an important indicator — but it does not determine everything.

So Why Does Product pH Still Matter?

To understand how a formulation works as a whole, we first need to consider its individual components.

pH is one of the most accessible and easily measurable indicators, and it can provide clues about formulation design.

Changes in skin pH after cleansing are multifactorial. Product pH, ingredients, formulation structure, usage conditions, and individual skin state all play a role.

Even so, product pH remains one of the few objective values that can be readily checked.

While we cannot assess every variable at once, knowing one measurable factor — pH — can help reduce some uncertainty when choosing a product.

pH is not a magic number.

But it can be a useful starting point for understanding how a cleanser may interact with your skin.

What Is the pH of Your Cleanser?

Do you know the pH of the cleanser you use every day?

This website provides a database of cleanser pH values.

Whether or not you check the product pH beforehand can affect how informed your choice is.

If you have a product you currently use or are considering purchasing, it may be worth taking a look.

¹ n = 14, volar forearm; measured using Skin-pH-Meter 900 (Courage + Khazaka)

² n = 63, volar forearm; Skin-pH-Meter 900 (Courage + Khazaka); 21 ± 1°C, 50 ± 2% humidity; three measurements; application 5 µL/cm²; tap water at 38°C; measured 10 minutes after drying

References

1) Lambers, H.; Piessens, S.; Bloem, A.; Pronk, H.; Finkel, P. Natural Skin Surface pH Is on Average Below 5, Which Is Beneficial for Its Resident Flora. Int. J. Cosmet. Sci. 2006, 28 (5), 359–370. https://onlinelibrary.wiley.com/doi/10.1111/j.1467-2494.2006.00344.x

2) Blaak, J.; Staib, P. The Relation of pH and Skin Cleansing. Curr. Probl. Dermatol. 2018, 54, 132–142. https://doi.org/10.1159/000489527

3) Springmann, S.; Blaak, J.; Grabmann, S.; Simon, I.; Staib, P. Impact of Cleansing Products on the Skin Surface pH. IFSCC Magazine. 2013, 1, 17-24