pH is a scale from 0 to 14 that measures the acidity or alkalinity of a substance compared to distilled water, which has a “neutral” pH of 7.0.

Anything below 7 is acidic.

Anything above 7 is alkaline.

Each unit on the scale represents a tenfold difference in the concentration of hydrogen ions in a solution. A pH of 4 is 10 times more acidic than a pH of 5, and 100 times more acidic than a pH of 6. This is an important detail: a small change in the number means a big difference in practice.

Broadly speaking, acids taste sour, while bases taste bitter. Lemon juice, for example, is sour because it contains approximately 5% citric acid and has a pH of 2.2, making it highly acidic. On the other hand, baking soda has a bitter taste because its pH is 9.0 (highly alkaline).

By the way, these are two things you should NEVER put on your face.

Here are some examples of basic (alkaline) and acidic substances:

• pH 1.5–3.5 = Stomach acid
• pH 2 = Lemon juice
• pH 5.5 = Rainwater
• pH 6.2–7.4 = Saliva
• pH 7 = Distilled water (the midpoint of this scale)
• pH 7.4 = Human blood
• pH 9 = Baking soda
• pH 9.0–10.0 = Soaps and laundry detergents
• pH 14 = Caustic soda (sodium hydroxide)

Our skin? Between 4.5 and 5.5.

Our skin is protected by what’s known as the acid mantle. This is a thin film on the surface of the stratum corneum, made up of fatty acids, lactic acid, pyrrolidone carboxylic acid, amino acids, and a whole bunch of other scientific terms.

Translated into plain language:

The acid mantle = a protective layer on the surface of the skin, made up of sweat, sebum, and dead skin cells. It is what gives the skin its pH, which ranges from 4.0 to 7.0, with an average value of 4.7.

The acid mantle is the skin’s first line of defense against pathogens, irritants, bacteria, fungi, viruses, and pollutants. It keeps the skin soft and supple—it does it all!

I’d use “soft and supple” here for a more natural, skincare-focused English phrasing.

Disrupting this wonderful protector can lead to adverse effects such as inflammation, atopic dermatitis, dehydration, dryness, sensitivity, and various forms of acne.

Disrupting this wonderful protector can lead to adverse effects such as inflammation, atopic dermatitis, dehydration, dryness, sensitivity, and various forms of acne.

Research suggests that skin with a pH below 5.0 may be healthier, better hydrated, and have a stronger barrier function than skin with a pH above 5.0.

The acid mantle is also an important natural regulator of the skin’s microbiome, a topic we’ll explore further below.

What Disrupts the Skin's pH?

Pollutants, pathogens, excessive occlusion, cleansing products and soaps, even water!

A good general rule of thumb is: the higher the pH of something, the more it disrupts the acid mantle and, consequently, the skin’s moisture barrier. So, while water itself isn’t necessarily bad, “hard water” is. Hard water is tap water with a high mineral content, which gives it a pH of 8.5 or higher.

Не е добро!  

То е признак, че киселинната ти мантия е нарушена. Избягвайте го на всяка цена! Целта е да почиствате кожата, без да я обезмаслявате от естествените ѝ мазнини.

The skin barrier of the stratum corneum is a network of ceramides, free fatty acids, and cholesterol that is highly dependent on pH.

Researchers at the University of California, San Francisco found evidence suggesting that skin pH may influence the skin’s ability to retain moisture and protect itself from external irritants.

When the skin is more acidic, certain enzymes function optimally, helping to produce the substances needed to build and maintain the skin’s protective barrier.

When the pH becomes more alkaline, these enzymes become less active. As a result, the skin barrier may recover more slowly and become weaker, allowing the skin to lose more water and leading to dryness.

Research has shown that disruption of the stratum corneum’s pH is associated with impaired barrier function, whether the shift is toward alkalinity, as with harsh cleansing products, or toward excessive acidity.

I’d make this flow more naturally and keep the scientific claim a little more measured:

The skin is home to around 1,000 different species of microorganisms. Not all of them are welcome guests.

Just as important is the acid mantle’s ability to help maintain moisture in the skin barrier and support the balance of the skin microbiome—the beneficial bacteria and other microorganisms that live on our skin.

Just as the beneficial bacteria in our gut help protect us against conditions such as Crohn’s disease, food intolerances, and autoimmune diseases, our skin microbiome also plays an important role in protecting us against conditions such as acne, rosacea, psoriasis, and dermatitis.

An acidic pH is one of the skin’s natural defenses against pathogens. Staphylococcus aureus—a bacterium associated with acne, atopic dermatitis, and skin infections—does not thrive in acidic conditions. Research has found a direct association between higher skin pH and S. aureus colonization. When skin pH rises above 6, this protective environment may become less effective.

Bacteria found on the skin’s surface, such as Staphylococcus epidermidis, Cutibacterium acnes (at low levels), and lactobacilli, metabolize sebum and produce fatty acids that help maintain an acidic pH.

In other words, the skin microbiome and the acid mantle exist in a symbiotic relationship. Disrupting one can affect the other.

No, this doesn’t mean we should stop cleansing our skin for fear of disrupting its acid mantle. Cleansing is important.

The key is to use a gentle, pH-balanced cleanser with a pH close to the skin’s natural range (4.5–5.5) to help maintain the integrity of your skin barrier.

Wait, should I use a toner after cleansing? It depends.

Toners are designed to help counteract the effects of high-pH cleansing products and bring the skin’s pH back toward a healthy balance.

But if you’re using a pH-balanced cleanser (highly recommended), you don’t need a toner.

Here I’d keep the slightly cheeky tone, but make the scientific wording more precise:

This brings me to why you should never put baking soda on your face… Baking soda has a pH of around 9, making it far too alkaline for the skin, and using it can disrupt the skin’s protective acid mantle.

In one rather disturbing study, researchers even tested alkaline products on babies without skin conditions, aged between 2 and 16 weeks, to see how the products affected their skin.

Ah, those scientists, I tell you…

Ultimately, they found that alkaline soap significantly raises the skin’s pH and disrupts its protective acid mantle.

At least temporarily.

The skin can restore its pH, but how quickly this happens depends on individual factors, how often the skin is washed, and which products are applied afterwards. Research has shown that repeated exposure to alkaline conditions can have a cumulative effect on skin barrier function.

Because not every product on the market is formulated with the health of your skin in mind, and not every influencer recommendation is backed by science.

Many brands rely on “natural” ingredients such as baking soda because they sound familiar, are inexpensive, and create the impression of a “deep cleanse.” But just because something is natural doesn’t mean it’s suitable for your skin.

At first, alkaline products may seem like they’re doing the job: they remove built-up sebum and leave your skin feeling “clean”—a sensation many people mistake for effectiveness. In reality, though, this can mean that your skin’s protective acid mantle has been disrupted.

Over time, this can contribute to more breakouts and skin irritation, as the skin may start producing excess sebum to compensate for the loss, while becoming more vulnerable to bacteria.

If a product promises to “deep cleanse” your skin with natural ingredients, check its pH. If it’s above 7, that feeling of “clean” may come at the expense of your skin barrier.

As a team of dermatology researchers puts it best:

“Most products recommended for sensitive skin have significant irritation potential, which is related to the product’s pH. Better regulation of advertising claims, including pH levels and the type of cleanser used, is needed for the majority of soaps and cleansing products.”

Skin pH is not an academic detail reserved for experts.

It is a functional parameter that helps determine whether your skin barrier is functioning properly, whether your microbiome is in balance, and whether the active ingredients you’re paying for are actually working.

Choosing cleansers with a pH close to the skin’s natural range (4.5–5.5) is one of the most important decisions you can make when it comes to skincare.

Not because it’s a trend, but because it is closely linked to the skin’s natural biochemistry.

YOGHSKIN De-Grease Calendula is a solid cleansing oil—oils don’t have a pH, so they don’t disrupt the acid mantle during cleansing, meaning you don’t need to worry about their alkalinity.