skin pH
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Skin pH is an indicator of the acidity or alkalinity of the environment present on its surface. Physiologically, the stratum corneum is slightly acidic, which contributes to the so-called acid mantle of the skin. It is not a single, separate coating, but a dynamic buffer system comprising water, sweat, sebum, free fatty acids, components of the natural moisturizing factor, and microbial metabolites. An appropriate pH regulates the activity of enzymes involved in the production of epidermal lipids, the controlled desquamation of corneocytes, and antimicrobial defense. An increase in pH can disrupt the integrity of the epidermal barrier, increase transepidermal water loss, and promote irritation. However, skin pH is neither a constant value nor a standalone measure of its health.
Skin pH - what is it
The abbreviation pH stands for the negative decimal logarithm of hydrogen ion activity. The pH scale is logarithmic, which is why a change of one unit corresponds to an approximately tenfold change in hydrogen ion activity. A value of 7 indicates a neutral reaction, values lower than 7 an acidic reaction, and values higher than 7 an alkaline reaction.
In dermatology, the skin surface pH is most commonly assessed, rather than the pH of the entire organ. In the viable layers of the epidermis, the reaction is close to neutral, whereas towards the stratum corneum, a pH gradient is formed leading to surface acidification. This is due, among other factors, to:
- free fatty acids generated during epidermal lipid processing,
- lactic acid, amino acids, and urocanic acid present in the natural moisturizing factor,
- secretions of the sweat and sebaceous glands,
- the sodium-hydrogen exchanger NHE1 and other proton transport mechanisms,
- the metabolism of the physiological skin microbiome.
An acidic environment supports the activity of β-glucocerebrosidase and acid sphingomyelinase, enzymes required for ceramide production. At the same time, it limits the activity of alkaline serine proteases, whose excessive action can weaken junctions between corneocytes, activate the PAR-2 receptor, and exacerbate inflammation.
Surface pH also influences the microbial ecosystem. Physiological pH favors many commensal microorganisms—those naturally colonizing the skin—while it may limit the proliferation of some opportunistic microorganisms. However, this does not mean that "skin acidification" alone cures an infection, acne, or an inflammatory disease.
Skin pH - what is the normal skin pH
In healthy individuals, the skin surface pH is typically acidic and most often falls within the approximate range of 4.5-5.9. In studies involving individuals who did not use cosmetics or wash the examined area prior to measurement, the mean pH was often below 5. However, there is no single normal value common to the entire body and all individuals.
The result is influenced, among other things, by:
- anatomical region – the pH of the armpits, groins, and interdigital spaces may be higher than the pH of the forearms or cheeks;
- age – after birth, the skin surface is closer to neutral and then gradually acidifies; in the elderly, the ability to regenerate the acid mantle may be impaired;
- sweat and sebum secretion, ambient temperature, and humidity;
- sex, hormonal balance, and individual characteristics;
- cosmetics, topical medications, washing, and shaving;
- skin diseases.
Elevated pH is observed, among others, in atopic dermatitis, certain forms of ichthyosis, diaper dermatitis, and within hard-to-heal wounds. In atopic dermatitis, an increase in pH may coexist with filaggrin deficiency, impaired lipid organization, increased protease activity, and colonization by Staphylococcus aureus. However, this is part of a complex pathophysiology rather than a single cause of the disease.
„pH 5.5” should therefore be treated as an approximate reference point rather than an absolute diagnostic standard. A result falling outside this range does not diagnose a disease, just as a normal measurement does not rule out damage to the epidermal barrier.
Skin pH - how to check it
The most accurate measurement of skin surface pH is performed using a flat electrode connected to an electronic pH meter. The electrode comes into contact with a thin layer of liquid on the surface of the stratum corneum. The test is non-invasive and usually takes from a few to several dozen seconds.
To ensure the result is comparable, measurement conditions must be controlled:
- Do not wash the tested area or apply cosmetics to it for a specified period before the test, usually at least several hours.
- Allow the skin to acclimatize before measurement in a room with stable temperature and humidity.
- Avoid prior physical exertion, intense sweating, occlusion, and rubbing of the skin.
- Measure the same anatomical region during subsequent follow-ups.
- Take several measurements and interpret their average, taking into account the equipment used.
Indicator test strips can provide an indicative result, but on a dry, uneven, and poorly moistened skin surface, they are significantly less precise. The reading is influenced by sweat, sebum, cosmetic residues, contact pressure, and subjective color assessment. A home test does not allow for diagnosing “disrupted skin pH”.
A more comprehensive analysis of the epidermal barrier may also include measuring:
- transepidermal water loss, i.e., TEWL,
- hydration of the stratum corneum using corneometry,
- sebum levels,
- erythema and pigmentation,
- temperature and topography of the skin surface.
Burning, itching, weeping, cracking of the skin, or persistent erythema are indications for a dermatological evaluation, rather than solely for a pH test.
Skin pH - what disrupts it
A change in pH can be a transient physiological reaction or part of epidermal barrier damage. The skin has a buffering capacity and gradually recovers its acidic pH, but frequent exposure to irritants can exceed its regenerative capabilities.
The most important factors disrupting skin pH and the skin barrier are:
- traditional alkaline soaps – their pH can be around 9-11; even brief washing temporarily raises skin pH;
- harsh surfactants – can strip lipids, increase TEWL, and denature proteins regardless of the product's pH itself;
- frequent washing, hot water, and prolonged soaking of the skin;
- excessive exfoliation with acids, retinoids, mechanical scrubs, or abrasive devices;
- alcohol-based preparations and disinfectants, especially when used frequently without regenerative skincare;
- shaving, friction, occlusion, sweat, and impermeable clothing;
- UV radiation, low air humidity, frost, wind, and environmental pollution;
- physiological skin aging;
- inflammatory dermatoses, infections, wounds, and certain systemic diseases.
It is not only the cosmetic's pH that matters. Two products with the same declared value can differ in irritation potential due to the type and concentration of detergents, fragrances, preservatives, and the ability of ingredients to bind with epidermal proteins. Furthermore, the term „pH neutral” is ambiguous: it can mean pH 7 or a pH close to the physiological pH of the skin.
Skin pH - how to restore proper pH
Restoring the physiological pH of the skin primarily involves reducing damaging factors and rebuilding the stratum corneum of the epidermis. The skin should not be acidified with lemon juice, vinegar, or homemade acid mixtures. Their uncontrolled concentration can cause irritation, chemical burns, increased inflammation, or post-inflammatory hyperpigmentation.
Daily care should include:
- mild syndet-type cleansing products, preferably with a pH close to the physiological pH of the skin;
- short washing with lukewarm water, without vigorous rubbing;
- an emollient containing appropriately selected humectants, occlusive substances, and lipids;
- preparations with ceramides, cholesterol, and free fatty acids, supporting the restoration of the lipid matrix of the stratum corneum;
- temporary limitation of peels, retinoids, and potent acids if burning, flaking, or hyperreactivity occurs;
- daily broad-spectrum photoprotection;
- treatment of diagnosed dermatosis according to the doctor's recommendations.
An in-office procedure does not set the skin's pH to a permanent level. However, it can support the regeneration of the epidermal barrier, increase hydration of the stratum corneum, and reduce symptoms associated with its damage. At Ambasada Urody, the following procedures are available that may be used in an individually planned therapy:
- Sonophoresis uses ultrasound waves to increase the penetration of appropriately selected active substances. Depending on the preparation used, it can support hydration, soothe irritation, and aid in the regeneration of the protective barrier.
- Environ treatments combine vitamin care with iontophoresis or sonophoresis. Their purpose is to deliver ingredients that support epidermal renewal processes, antioxidant protection, and the maintenance of proper hydration. The intensity of the therapy should be adapted to the skin's current tolerance.
- Environ ionopeels utilize controlled exfoliation combined with iontophoresis. They can improve skin structure and hydration, but in the case of a damaged barrier, severe burning, or active inflammation, they require cautious qualification.
- Oxygen infusion enables the superficial administration of moisturizing and soothing preparations using oxygen under pressure. The treatment can improve short-term hydration and skin comfort without mechanically compromising the epidermis.
- DermaClear combines hydrodermabrasion, cleansing, exfoliation, and the application of moisturizing and antioxidant substances. The selection of solutions and parameters should take into account the condition of the epidermal barrier, as excessive exfoliation may temporarily increase skin reactivity.
- HydraFacial includes cleansing, controlled exfoliation, extraction of impurities, and the delivery of nourishing preparations. It can support skin hydration, but with an impaired barrier, acids, vacuum strength, and booster composition must be chosen with caution.
- OxyGeneo combines superficial exfoliation with the application of active ingredients and a tissue oxygenation effect. The procedure can improve skin smoothness and hydration, but its intensity should correspond to the current tolerance of the epidermis.
- INDIBA MED uses radiofrequency current for a controlled effect on tissues. It can support microcirculation and regenerative processes, but it does not directly affect the pH value of the skin surface.
- Facial endermologie is a mechanical method of tissue stimulation, used among other things to improve microcirculation and skin condition. It serves as a supportive procedure, not a method for rebuilding the acid mantle.
- Mesotherapy can improve skin hydration and quality through intradermal administration of appropriately selected preparations, most commonly containing hyaluronic acid. It does not directly normalize surface pH, and breaching skin continuity requires proper qualification and post-treatment care.
In the presence of active inflammation, erosions, severe itching, infection, or a significantly damaged epidermal barrier, priority is given to dermatological diagnostics and treating the underlying cause. Exfoliating, vacuum, thermal, and skin-barrier-disrupting procedures may require postponement during such a period. The choice of treatment should result from clinical assessment, skin type, and contraindications, rather than solely from a single pH measurement.
