Skin pH: Small Number, Big Impact?

The skin acidity (pH) and the impact on skin health and skin microbiome.

Question: What’s the average pH of the skin?I posted this as a quiz last week — and wow, the responses came flooding in! The correct answer is pH 4,7. And not 5,5, 5,0 or 4,1!!

But let’s be honest… many (para)medical professionals and skin therapists got it wrong. Surprising? Maybe. Then again… maybe not. The skin’s pH is still an overlooked topic, even though it plays a starring role in skin health, immune defense, and barrier function. That’s a bit worrying — because pH is crucial.Time for more healthcare professionals to dive into this topic! In my books, I explain in detail why skin pH matters and, more importantly, how to apply that knowledge in practice. You’ll find a brief summary on skin pH below.

The acidity of the skin, also known as the skin pH

One of the key factors for maintaining healthy skin is its specific pH level. The skin surface has an acidic pH and is therefore often referred to as the “acid mantle.” This acidity and the buffering capacity of the outermost layer of the skin, the stratum corneum (SC), are essential for healthy skin. They help maintain a balanced skin microbiome and support key physiological processes such as the formation of an optimal lipid barrier structure and the overall equilibrium in the SC.

As early as 1892, the acidic nature of the skin was first described. In 1982, Heuss concluded that "the entire healthy skin shows an acidic reaction, although the pH varies depending on the area of the body." It wasn’t until the 1920s and 30s that researchers began to recognize the role of surface pH in microbial defense. It was noted that sweat residues evaporate and leave behind a more concentrated, acidic layer. However, the acid mantle is not the only defense mechanism — sebum and the continuous shedding of skin cells also play a role in this protective function.

For a long time, it was believed that the skin’s acidity was primarily a result of exocrine secretions from glands, helping to regulate the skin’s flora and assist in cleansing. However, more recent studies have provided greater insight into the development, components, and role of skin pH, even in the deeper layers of the stratum corneum. The acidic environment plays a central role in maintaining the barrier function, normal lipid maturation, and healthy desquamation (shedding) of the skin.

In the early 20th century, researchers Schade and Marchionini (1928) discovered that covered skin is less acidic than skin exposed to the atmosphere, and that pH varies by body region. They assumed this was due to the impregnation of the stratum corneum with acidic sweat components, since areas with apocrine glands or skin folds showed a more neutral or even alkaline pH. Since the 1950s, the development of the flat glass electrode has allowed for more accurate pH measurements on the skin surface.

Why Skin pH Is So Important?

The acidity of the skin plays a crucial role in:

• Maintaining the barrier function of the stratum corneum;

• Preserving the integrity and cohesion of the SC;

• Supporting overall skin homeostasis;

• Aiding in lipid production and barrier formation;

• Supporting extracellular lipid processing;

• Regulating proteolytic enzyme activity, crucial for proper desquamation;

• Sustaining a healthy resident skin flora;

• Ensuring antimicrobial resistance through a stable acidic environment.

  
  

Even slight deviations in pH can disrupt these processes. Recent scientific studies have shown that the skin pH differs in conditions such as acne, eczema, rosacea, and aging skin. But the big question remains: Is an altered pH the cause of these issues, or a consequence of other underlying factors?

External Factors & Product Choice Matter

In recent years, there has been growing scientific interest in how external influences — such as water, sweat, skincare products, and cleansers — affect the skin’s pH. Surprisingly, this knowledge is rarely applied in practice. Only a few skincare brands produce products with a pH that matches healthy skin — and clearly indicate this on the label. For most other cosmetic and skincare products, the pH is either unknown or kept secret under the label of "proprietary formula."

To better understand the development and treatment of skin disorders, insight into skin pH and the impact of external influences is essential — not only for dermatologists and skin therapists prescribing or recommending products, but also for manufacturers and individual users. This knowledge can improve everyday skin care, both for healthy skin and for preventing or managing sensitive or damaged skin.

My Advice

When choosing skincare products, don’t just look at the ingredients — also check the pH. Prevention is always better than cure! And read my book for more details about skin acidity and the impact on our skin microbiome.

Go to 'Our books', and direct link directly to Amazon: https://www.amazon.com/dp/B0DJYK5KXC

With love,

Marcelline Goyen, BSc skin therapy (dermal therapist) & author

#skinhealth #pHbalance #acidmantle #skintherapy #healthcareprofessionals

Ps 1: In future blog posts, I will explore this topic further. I’d love to hear your thoughts, experiences, or questions in the comments. Your feedback is always welcome!

Ps 2: Feel free to share this blog with your network so more people dealing with skin problems can benefit from this knowledge. Just click one of the buttons below. Thanks so much!

Ps 3: If you would like to receive an author's copy to write a review about, I can arrange that for you. And if you have any questions, I'd love to hear from you. In my Book Shop on my website www.skin-gut-axis.com you can find this book, including the Table of Content, and also the other books I wrote about the skin-gut axis.