Eczema, Water and Skin Acidity: Why pH Matters More Than We Thought
- Marcelline Goyen
- Mar 9
- 8 min read
Updated: Jul 5
By Marcelline Goyen, BSc
Dermal Therapist, Skin-Gut Axis Specialist & Author
Published on: March 9, 2026
Table of content
Eczema and Why Skin pH Matters More Than We Thought
Unfortunately, atopic dermatitis and chronic eczematous lesions are becoming increasingly common global health concerns. While individuals with a resilient skin barrier and a healthy skin pH can interact with water during a daily shower or swim without any complications, this exposure is frequently a highly irritating, painful, or burning experience for eczema patients.
This hyper-reactivity occurs not only because the epidermal barrier is already severely dehydrated and structurally compromised, but also because exogenous water exposure can further disrupt skin homeostasis by directly elevating the skin surface pH. Understanding the underlying molecular kinetics of this process is essential for achieving long-term therapeutic relief.
The average skin pH (acidity)
For decades, skin professionals, beauticians, and dermatologists have been taught that the physiological pH of human skin is around 5.5. This specific number has become an absolute dogma within cosmetic science and skincare formulation. However, modern dermatological research paints a far more nuanced, biology-backed picture: classic clinical trials, including the foundational work by Lambers et al. (2006), demonstrate that the average natural pH of healthy human skin is considerably lower, typically resting around 4.7, with reported physiological ranges fluctuating between 4.2 and 5.8 *).
This biochemical distinction may seem minor at a superficial glance, but it carries profound implications for epidermal lipid processing, cellular enzymatic activity, and the stabilization of the cutaneous microbiome.
*) I discuss the average skin pH in more detail in a related post, which you can find here: Skin Acidity (pH): Small Number, Big Impact to Our Skin and Microbiome?
The importance of an acidic skin surface
The slightly acidic nature of the outermost epidermal layer—biologically referred to as the acid mantle—is a mandatory requirement for numerous metabolic processes within the skin. As outlined by Fluhr & Elias (2002), the formation and function of this acid mantle are critical for the lifecycle of keratinocytes. Newly formed keratinocytes originate in the deep stratum basale, after which they gradually migrate upwards through the epidermal strata while undergoing a highly complex process of cellular maturation. Ultimately, they differentiate into corneocytes—the flattened, enucleated cells that constitute the stratum corneum, which serves as the physical shield of the human body.
A stable, highly specific acidic pH is required for the optimal functioning of endogenous enzymes responsible for:
Sphingomyelinase and Beta-Glucocerebrosidase activity: Enzymes that process essential lipids (ceramides, cholesterol, and free fatty acids) within the extracellular matrix.
Structural Barrier Formation: Ensuring the dense, brick-and-mortar organization of the lipid bilayer.
Controlled Desquamation: Regulating serine proteases (like kallikreins) to allow seamless shedding of dead corneocytes without visible scaling.
When the pH of the skin surface deviates for prolonged periods—either becoming too alkaline or excessively acidic—these enzymatic pathways instantly destabilize. The physiological consequences manifest as impaired barrier synthesis, elevated transepidermal water loss (TEWL), chronic scaling, and a significantly higher vulnerability to external chemical irritants and aeroallergens.
Skin pH and the microbiome
The skin’s acidity also acts as the primary ecological gatekeeper for the cutaneous microbiome. Beneficial commensal microorganisms, most notably Staphylococcus epidermidis, thrive optimally within a slightly acidic environment (pH 4.7–5.0). As supported by Sanford & Gallo (2013), these resident microbes actively contribute to local dermatological health through several distinct pathways:
They naturally inhibit the colonization and proliferation of pathogenic, opportunistic microbes.
They synthesize defensive antimicrobial peptides (AMPs).
They produce organic acids (like lactic acid) that help maintain the localized acidic skin microenvironment.
This creates a highly sophisticated, mutually beneficial biological loop: a healthy acidic pH sustains commensal microbes, and those microbes in turn synthesize the biochemical components required to defend the acid mantle and support skin-guided immune tolerance.
However, when the skin surface pH rises toward neutrality or alkalinity, this fragile ecological balance shifts dangerously. Pathogenic opportunistic microbes—including Staphylococcus aureus and fungal pathogens like Candida albicans and Malassezia—are less sensitive to elevated pH levels and rapidly proliferate under alkaline conditions.
This severe microbial dysbiosis is a classic hallmark of inflammatory skin diseases such as atopic dermatitis, where an elevated skin pH has been consistently documented (Cork et al., 2009). The pathogenic overgrowth of S. aureus in these patients directly correlates with increased tissue inflammation, itch severity, and barrier degradation. Managing these pathogens effectively requires a multi-faceted approach; while short-term medical interventions target acute flares, restoring the physiological skin pH is vital for long-term barrier resilience and preventing recurrent colonization.
Water exposure: an underestimated factor
One of the most systematically underestimated lifestyle influences on skin homeostasis is simple, daily contact with water. Everyday activities such as washing, showering, bathing, or swimming in chlorinated pools all temporarily force the skin surface pH upward. Because tap water typically features a neutral to slightly alkaline pH (ranging between 7.0 and 8.0), it acts as a chemical stressor on the acid mantle. Clinical data indicates that following water exposure, the pH of the skin can remain elevated and vulnerable for several hours!
Healthy, resilient skin possesses an innate buffering capacity that allows it to gradually re-acidify its surface through lipid metabolism, sweat components (like lactic acid), and active commensal microbial fermentation. However, in patients dealing with genetic barrier defects (such as filaggrin mutations) or active eczema, this natural buffering kinetics recovery process is significantly delayed or incomplete. As a consequence, the skin remains trapped in a prolonged alkaline state, drastically increasing its susceptibility to severe irritation, microbial dysbiosis, and chronic itching.
When skincare interferes with the buffer system
Interestingly, not only neutral (water, pH 7,0), or alkaline substances but also overly aggressive skincare regimens can severely deplete the skin's natural buffering capacity. For instance, the frequent, unmonitored application of strong chemical exfoliants like alpha-hydroxy acids (AHAs)—which are often formulated at highly acidic pH values well below 4.0—can temporarily alter epidermal cellular turnover. Many skin professionals and clients recognize the immediate, short-term visual effects: a smoother texture, accelerated desquamation, and enhanced radiance.
However, with chronic, excessive usage, this practice can overwhelm the skin's regulatory mechanisms, leading to persistent erythema, localized inflammation, barrier thinning, and intense skin sensitivity. This occurs because the repeated biochemical shock prevents the skin from establishing its baseline buffering kinetics. In clinical practice, a temporary cessation of aggressive chemical exfoliants is essential to facilitate epidermal barrier rehabilitation and restore the skin's natural buffering kinetics.
The role of daily hygiene
Modern lifestyle and daily hygiene habits heavily dictate the structural integrity of the acid mantle. A vast majority of the population—particularly younger demographics—frequently indulge in prolonged, hot showers combined with conventional foaming cleansers. As demonstrated by Korting & Hübner (1990), traditional bar soaps possess highly alkaline formulations, often reaching pH values well above 9.0. When these harsh surfactants are combined with prolonged water exposure, the epidermal lipid matrix is repeatedly stripped.
For individuals navigating sensitive, acne-prone, or eczematous skin conditions, this hygiene routine can rapidly accelerate disease progression. To mitigate this damage, practical clinical recommendations include:
Strictly limiting the duration of showers and baths.
Avoiding excessively hot water, which melts essential skin lipids.
Eliminating alkaline bar soaps and replacing them with pH-balanced, non-foaming syndets.
Utilizing water-only cleansing on severely compromised barrier zones when appropriate.
In acute, hypersensitive cases of atopic dermatitis, reducing washing frequency to every few days can provide the physiological rest necessary to support optimal barrier recovery and acid mantle reconstruction.
Skin pH within the skin–gut axis
While skin surface pH is historically discussed purely as an isolated dermatological metric, advanced clinical biology requires us to view this parameter through the systemic framework of the skin–gut axis. Both the gastrointestinal tract and the integumentary system host dense, complex microbial ecosystems that constantly communicate with the human immune system and modulate physical barrier integrity.
Gastrointestinal dysbiosis, low-grade systemic inflammation, and increased intestinal permeability (leaky gut) can alter systemic immune responses, which subsequently travel to the skin, down-regulating the synthesis of critical structural proteins and lipids. A compromised epidermal barrier is far less capable of maintaining its optimal acidic pH.
From this interconnected perspective, maintaining a stable, acidic skin environment is not merely a localized aesthetic goal; it is a vital external component of the broader ecological and immunological balance that underlies the skin–gut connection. Recognizing how everyday variables like water exposure, daily hygiene habits, and cosmetic interventions alter skin acidity is a crucial piece of the physiological puzzle in achieving long-term, systemic skin wellness.
📘 Advanced Clinical Studies & Curriculum In The Amazing World of the Skin-Gut Axis textbook series, a dedicated chapter is reserved for the advanced biochemistry of skin pH, sebum composition, and long-term nutritional strategies for deep internal barrier repair. Discover the complete masterclass curriculum at www.skin-gut-axis.com.
Frequently Asked Questions (FAQ)
What is the ideal pH for human skin, and why does it matter for eczema?
Healthy human skin thrives at an average pH of around 4.7, which is significantly more acidic than the historical belief of 5.5. For eczema patients, maintaining this high acidity is critical because the enzymes responsible for building the skin's protective lipid barrier and keeping moisture locked in can only function optimally in an acidic environment.
How exactly does tap water worsen eczema itching and dryness?
Tap water typically has a neutral to slightly alkaline pH (around 7 to 8). When water touches compromised skin, it temporarily strips away natural lipids and raises the skin's surface pH. Because eczema skin has a damaged buffering capacity, it cannot quickly re-acidify itself. This leaves the barrier open, accelerating transepidermal water loss (TEWL) and exposing nerve endings, which triggers severe itching.
Why does an elevated skin pH lead to bacterial infections like Staph?
Beneficial, protective skin bacteria thrive in an acidic environment. When your skin pH rises and becomes more alkaline (due to water or harsh soaps), these friendly microbes decline. This allows opportunistic pathogens like Staphylococcus aureus to rapidly multiply. S. aureus colonization is a major driver of the intense inflammation and flare-ups seen in atopic eczema.
Can chemical exfoliants like fruit acids help restore the skin's acid mantle?
While mild acids might seem helpful for an acidic skin surface, frequent use of strong chemical exfoliants (pH below 4.0) can actually achieve the opposite. They shock the skin's delicate regulatory systems, stripping essential lipids and weakening the barrier. For compromised or eczema-prone skin, it is best to avoid aggressive peeling products to allow the skin's natural buffering system to fully recover.
Scientific References
Schmid-Wendtner M-H & Korting H. (2007) pH and Skin Care. ABW Wissenschaftsverlag GmbH ISBN 978-3-936072-64-8
Goyen Marcelline (2019). The skin-gut connection. Opus Nova - ISBN 9789463456210 Volume I
Goyen Marcelline (2023 / 2024 / 2025). The amazing world of the skin-gut axis, including the role of the microbiome. Volume II
Lambers H. et al. (2006). Natural skin surface pH is on average below 5, which is beneficial for its resident flora. International Journal of Cosmetic Science. IJCS
Proksch E. (2018). pH in nature, humans and skin. Journal of Dermatology. JDERM1
Fluhr J.W., Elias P.M. (2002). Stratum corneum pH: formation and function of the acid mantle. Exogenous Dermatology. ResearchGate
Ali S.M., Yosipovitch G. (2013). Skin pH: from basic science to basic skin care. Acta Dermato-Venereologica. ActaDV
Cork M.J. et al. (2009). Epidermal barrier dysfunction in atopic dermatitis. Journal of Investigative Dermatology. JID
Sanford J.A., Gallo R.L. (2013). Functions of the skin microbiota in health and disease. Seminars in Immunology. ScienceDirect
Korting H.C., Hübner K. (1990). Influence of repeated washings with soap and synthetic detergents on skin pH and resident flora. International Journal of Cosmetic Science. ActaDV2
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Marcelline Goyen, BSc | Dermal Therapist | Skin-Gut Axis Specialist | Author
Founder of www.skin-gut-axis.com
About Marcelline Goyen, BSc Marcelline Goyen, BSc, is a dermal therapist (formerly practicing), international educator, and author specializing in the complex interactions of the skin-gut axis. With over two decades of clinical experience, she is known for her pioneering work on the skin-gut-brain connection and integrative approaches to skin health. To make her knowledge more widely accessible, her work has culminated in the publication of two books, which are used as reference works in the field of holistic skin rehabilitation. Alongside her writing, she shares her insights globally through masterclasses and webinars.
Discover more about her books and clinical vision at www.skin-gut-axis.com, or connect with Marcelline on LinkedIn.
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