Dr Barry Cohen discusses the importance of pH in the efficacy of skincare
Cosmeceuticals and skincare represent a 15 billion dollar a year global industry1, with no foreseeable slowdown in growth. Tens of thousands of products may be found on the market, sold through practitioners’ offices, medical spas, retail outlets, online, and at mass-market venues, with even more money spent on in-clinic and spa treatments in the form of chemical peels. Much has been written about various ingredients in the relevant literature. Most references, however, focus solely on the efficacy of products as a function of concentration of the active ingredients. In fact, even more important than the concentration of the active ingredient is the pH, or level of acidity of the product. The combination of active ingredient concentration and pH is referred to as bioavailability.2 Bioavailability is a term used to describe the actual percentage of active ingredients (AI) delivered and available to act on the skin. Many products tout their percent AI, which is actually an, ‘initial concentration’ – without mentioning the pH. This %AI however, is only of benefit to the consumer when the AI actually reaches and penetrates the skin. Unbeknown to most consumers is that the level of pH of the final product has a direct correlation to the products effectiveness.
In order to understand the importance of pH in skincare, one first must understand some basics of skin pH. The skin, our largest organ, maintains a healthy pH in the range of 4-4.9.3 The purpose of this relatively acidic pH is to help in the resistance of pathogen invasion, especially bacteria, in the environment.4 Additionally, several crucial enzymes involved in the maintenance of this so called ‘Acid Mantle’ of the skin are dramatically impacted by the pH of the skin.3 Many factors influence the pH of the skin, and these include but are not limited to; age, hygiene, nutrition, various disease states, seasonality, and topical product applications.5,6 This leads to the discussion of the pH of skincare products and its role in assessing a product’s efficacy. For this, it is important to remember that the pH scale is logarithmic, which means for every one point shift in the pH of a product there is a tenfold difference in effect.
Unbeknown to most consumers is that the level of pH of the final product has a direct correlation to the products effectiveness.
The role of pH in skincare
One of the most common ingredients in skincare is the alpha hydroxy acid; glycolic acid. Most products will denote the percentage of glycolic acid in the content list, but few will tell you the product pH. A 70% glycolic acid product can be buffered to be as mild and as innocuous as water at a neutral pH of 7, whereas a relatively low concentration of 20% glycolic acid at a pH of 3 would be quite potent. Clearly, knowledge of both the concentration and pH of a product’s active ingredient is critical in assessing its potential efficacy. So, what is an ideal pH for a treating product, and when is a more neutral pH of a skincare product more appropriate? Fundamentally, many of the active ingredients with known clinical efficacy in anti ageing are various acids: alpha hydroxy acids, beta hydroxy acids, ascorbic acid (vitamin C), retinoic acid (vitamin A derivatives). All of these products have a higher bioavailability and demonstrate greater efficacy as their pH approaches a therapeutic range of 3-4. The creation of a ‘micro burn’ generates an inflammatory process which aids the anti-ageing effect of the product. As an example, if one compares two glycolic acid product preparations, each at a concentration of 10% acid, one at a pH of 3, and one at a pH of 5, the product at the lower pH will be 100 times more effective.7 It is important to remember however, as a treating professional, more is not always better – especially at first. If a patient is started on a product at an ideal treatment pH, it may produce significant initial skin irritation. In fact, it is often wise to gradually increase the bioavailability of an acid to allow the patient’s skin to acclimate to the more acidic environment. Many of the more sophisticated treatment regimens, including Retin-A, have differing available concentrations as well as pH levels to allow a patient the ability to acclimate to an increasing bioavailability. Most patients require 2-4 weeks at various treatment levels to acclimate their skin and, in the early stages of treatment, education of the patient is critical with any potent acid product. Initial redness and mild irritation is not only expected, but also demonstrative of helpful results. Most irritation is ephemeral in the typical patient, and requires only supportive care.
When is a higher pH preferable or indicated?
Firstly, not every patient can tolerate relatively acidic products. Some patients’ skin demonstrates an ongoing sensitivity to acidic products, precluding them from the various acid treatments on the market. In those cases, there are alternatives. Specifically, product categories such as peptides, cytokines, growth factors, and various moisturisers and sun blocks, do not require an acidic pH to demonstrate efficacy. Particularly, the peptide and cytokine categories, from my experience, have shown real promise in the anti-ageing realm, and can be used on even the most sensitive skin. Of course, many of the mass-market products are intentionally buffered to more neutral pHs to reduce irritation and potential return sales. The truth is, despite higher levels of acid concentration, the products have limited therapeutic effect.8 As a treating practitioner, it is critical to know that as people age their skin pH tends to rise above five, which is higher than a normal physiologic ideal to maintain barrier function of the acid mantle. With this increase of pH comes lower resistance to bacteria as well as an increased risk of certain pathologic disease states. Particularly in the elderly (determined as upper seventies to eighty), use of skincare products in the pH range of 3-4 is ideal.9 PH of skin and skincare products has also been shown to play a significant role in acne treatment. The most common bacterial cause of acne is Proprionobacterium acnes, which flourishes when the skin pH rises above six. Studies have shown that cleansing acne-laden skin with an acidic-based soap reduces the active acne lesions significantly, as compared with a more traditional alkaline soap.10 Common treatments of acne therefore include cleansers at a lower pH. Classic examples include the beta hydroxy acids as cleansers in acne care, as well as retinoic acid and its derivatives.11 Interestingly, a survey of pH levels was completed of several dozen common soaps, synthetic detergents (syndets) and cleansers.3 The range of pH was noted to be between 3.61 to as high as 12.35, with the syndets being the lowest. As treating clinicians, we encounter many cutaneous disorders as well as complaints of anti-ageing. Indeed, there are many choices of therapy for these varying complaints. It is critical to remember that the basics of therapy (and sometimes causation) for patient complaints are their cleansers and soaps. Use of highly alkaline cleansers and soaps are frequently contributory to various dermatoses,12 intertrigo, as well as ageing, and therefore the importance of the selection of an appropriate cleanser at a relatively low pH cannot be overstated.
As clinicians we spend significant energy focusing on the percentage of active acid ingredients with which we treat our patients. In fact, it is the pH of most acid based products that influence their efficacy and potency.
In conclusion, we have learned much in the last decade about the importance of pH of the skin as it relates to both ageing and pathologic conditions. Similarly, the role of pH in topical skincare products has emerged as a major factor in product efficacy. As clinicians we spend significant energy focusing on the percentage of active acid ingredients with which we treat our patients. In fact, it is the pH of most acid based products that influence their efficacy and potency.
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