Skincare

THE pH factor

Ingredient percentages may dominate skincare marketing, but pH often determines whether a product actually works. Ellen Cummings explores why understanding formulation acidity is essential for skin barrier health

If the phrase “pH scale” conjures up memories of school chemistry lessons, you’re not alone. For many therapists, pH might feel like an abstract scientific concept rather than a practical treatment-room consideration. Yet behind the familiar marketing language of ingredient percentages and “clinical strength” formulations lies a more fundamental factor determining whether a product will actually perform on the skin.

Put simply, pH measures how acidic or alkaline a substance is, on a scale from 0 to 14. Human skin sits slightly on the acidic side, typically around pH 4.5–5.5. This delicate balance forms part of what is known as the acid mantle – the thin, slightly acidic film created by sebum, sweat and skin lipids that coats the surface of the skin.

The acid mantle plays a crucial role in maintaining barrier integrity, supporting healthy cell turnover and keeping the skin’s microbiome in balance. Disrupting it can increase transepidermal water loss (TEWL), weaken barrier function and make skin more vulnerable to irritation and inflammation. For professional therapists, understanding how pH interacts with active ingredients, treatment sequencing and homecare routines can be the difference between predictable results and compromised outcomes.

Why pH matters

Despite its importance, pH is often overlooked in everyday treatment planning. According to Fiona Brackenbury, an independent skincare consultant and educator with over 30 years’ industry experience, this gap between theory and practice is common.

“From a practical perspective, pH should absolutely be considered in day-to-day treatment planning,” she explains. “Skin pH is pivotal in maintaining the integrity of the epidermal barrier. The pH plays a fundamental role in how the skin responds to treatments, how ingredients perform, and ultimately the results a client experiences.”

Healthy skin, she notes, thrives in a slightly acidic environment. “This environment supports barrier integrity, enzymatic activity involved in cell turnover, and the balance of the skin microbiome. When the skin’s pH becomes too alkaline, barrier disruption and increased transepidermal water loss can occur.”

Anne Marie Joseph, a skin specialist at Glow Salon in Chester with over 25 years’ experience, agrees that pH awareness is essential but often underemphasised.

“In my opinion, the industry tends to place greater emphasis on key ingredients and their percentages, often overlooking the importance of pH balance,” she says. “While active ingredients are important, the pH of a formulation significantly influences how those ingredients interact with the skin.”

The chemistry behind active ingredients

One of the biggest misconceptions in professional skincare is that higher percentages automatically translate into stronger or more effective results. In reality, the behaviour of many active ingredients is heavily influenced by the pH of the formulation.

Brackenbury explains that pH affects the chemical state of certain ingredients, determining whether they are able to penetrate the skin and perform as intended.

“Over the last few years, we have focused on highlighting percentages; however, they only tell part of the story,” she says. “The percentage indicates how much, but pH indicates how the products will behave on the skin and how powerful they are.”

Alpha hydroxy acids (AHAs) offer a clear example. For these acids to exfoliate effectively, a sufficient proportion must be present in their “free acid” form – something strongly influenced by the formulation’s pH.

“A product containing a higher percentage of glycolic or lactic acid but formulated at a higher pH may actually deliver a milder exfoliating effect than a lower-percentage product formulated at a more acidic pH,” she explains.

In practice, this means a 10% glycolic acid product formulated at a lower pH may produce more visible smoothing and exfoliation than a 15% product formulated at a higher pH.

Joseph highlights a similar dynamic when performing professional peels. “A 20% peel with a pH of around 0.5 can be extremely aggressive and damaging to the skin barrier,” she says. “In contrast, a 5% peel with a pH of around 2 can often be safer while still delivering effective results.” In other words, pH doesn’t just influence efficacy – it also plays a significant role in tolerability and safety.

The impact of homecare

For many therapists, the first clues that pH imbalance is affecting the skin appear during consultations. “One of the most important parts of the skin consultation is assessing a client’s skin barrier function,” says

Brackenbury. “The pH of their homecare products is an important consideration, though it’s rarely something clients are aware of.”

Rather than asking directly about pH, she advises therapists to focus on product types and routines. “I recommend understanding the types of products they use, how frequently they exfoliate, and whether they are layering multiple active ingredients such as vitamin C with exfoliating acids.”

In barrier-compromised clients, certain patterns appear repeatedly. Over-exfoliation is particularly common, especially when multiple actives are used simultaneously.

“Clients may combine exfoliating toners, resurfacing serums and vitamin C without fully understanding how these formulations interact with the skin’s natural pH balance,” she explains.

“Frequent use of low-pH formulations without adequate recovery time can leave the skin in a persistently disrupted state.”

Joseph sees similar issues in practice. “Many clients are layering multiple products without realising that combining several active formulations with different pH levels can disrupt the skin barrier,” she says.

She also highlights the overuse of retinol as a recurring issue: “A common pattern I observe in compromised skin is the overuse of high-percentage retinols without first strengthening the stratum corneum through a gradual, low-strength introduction.”

Sequencing treatments for optimal results

Understanding how pH influences product performance can also help therapists structure more effective treatment protocols. According to Brackenbury, products with lower pH levels – such as chemical exfoliants – should generally be used earlier in the treatment sequence. “Alpha hydroxy acids and beta hydroxy acids rely on an acidic environment to remain active, so applying them onto freshly cleansed skin allows them to work as intended,” she explains. However, she warns against moving between extreme pH levels during a single treatment.

“It’s best to transition back towards neutral or slightly acidic formulas as you layer your routine. Avoid ‘yo-yoing’ between pH extremes in a single treatment, as this can disrupt the skin’s natural balance and make the barrier more vulnerable.”

Vitamin C is a good example of where sequencing matters. L-ascorbic acid requires a low pH to remain stable and penetrate the skin effectively, but applying it immediately after an intensive exfoliation step could stress the barrier further.

“When treatments move into recovery phases, the focus should shift towards restoring and supporting the skin barrier,” Brackenbury notes.

When pH goes wrong

Both therapists have seen situations where incorrect pH levels have compromised treatment outcomes. Brackenbury explains that when the skin becomes too alkaline, key processes within the barrier begin to break down. “The enzymes responsible for producing ceramides and other barrier lipids function optimally in an acidic environment, so an increase in pH reduces lipid production, which then weakens the stratum corneum.”

At the same time, excessive acidity can also create problems. “Extremely low pH can accelerate corneocyte shedding, which is why acids are effective exfoliants. However, excessive exfoliation can lead to barrier thinning and sensitivity.”

One of the most common clinical signs of pH imbalance is increased reactivity. “When the skin’s acid mantle is disrupted, the microbiome and barrier function can become less stable, making the client more likely to experience stinging and redness in reaction to products that would normally be well tolerated.”

Joseph recalls similar issues from earlier in her career when more aggressive peel formulations were common. “Previously, TCA solutions were often in a fine liquid form that penetrated the skin very rapidly,” she says. “This could easily lead to excessive barrier damage.” Clinical signs included burning sensations, redness, hypersensitivity and prolonged downtime.

Supporting recovery after advanced treatments

After professional resurfacing procedures, managing pH becomes even more important.

“When a client is undergoing in-clinic resurfacing or advanced treatments, homecare should always be carefully adapted to support barrier recovery,” says Brackenbury.

She recommends simplifying routines and prioritising barrier-supportive products such as gentle cleansers, hydrating serums and moisturisers rich in lipids and ceramides, alongside daily broad-spectrum SPF.

“I recommend avoiding actives such as ascorbic acid, retinoids or exfoliating acids,” she adds. “It’s important to recognise the cumulative pH load on the skin.”

Joseph takes a similar approach. “After resurfacing treatments, I typically advise clients to reduce or pause strong actives such as BHAs, PHAs and retinol. This allows the skin barrier time to recover.”

Closing the pH knowledge gap

While awareness of pH is improving within the industry, both experts believe there is still room for greater education. “Therapists understand that the skin’s natural pH is slightly acidic,” says Brackenbury, “but there is often less clarity about the exact pH in the products they use.”

Greater transparency from brands would help professionals make more informed decisions about treatment planning and product layering, she adds. Joseph agrees. “pH literacy among therapists is limited,” she says. “While it is introduced during college training, it is often overshadowed by marketing that focuses heavily on ingredient percentages.”

Ultimately, improving pH literacy could lead to more controlled treatments, better recovery and more consistent clinical outcomes. As Brackenbury puts it, “By recognising how each step in a protocol may alter the skin environment, therapists can balance efficacy with barrier support.” And in a results-driven industry, that balance may be the real marker of advanced professional practice.