Is there a correlation between abnormal skin pH levels and acne symptoms?

Svetlana Tkachenko , Ph.D., Associate Professor of the Department of Dermatology, Venereology and Medical Cosmetology, Kharkov National Medical University (Kharkiv)

Given the active growth of Propionibacterium acnes with mild alkalization of the skin, it can be assumed that normal acidic pH values at the skin surface are important for inhibiting the colonization of propionibacteria and the manifestation of acne. Reducing the level of skin acidity using a microiontophoretic system has demonstrated a significant therapeutic effect in patients with acne, which makes it possible to consider this method as an adjuvant (auxiliary) treatment of acne along with chemical peels.

It is well known that increased pH (i.e., alkalization) can be associated with the pathogenesis and severity of many dermatoses, including acute eczema, contact and atopic dermatitis, ichthyosis, acne, and candidiasis.

Sebum free fatty acids are partly involved in the creation of the skin's acid mantle. Considering the excess sebum in patients suffering from acne, one can count on acidification of the surface of their skin, but data from scientific and medical literature suggests the opposite. Therefore, keeping in mind that the growth of P. acnes is activated by mild alkalization of the skin, we can assume the importance of maintaining normal pH values of the skin surface to curb its colonization and, at the same time, the manifestation of acne.

Analysis of research results

In recent years, there have been attempts to discover a previously uncultivable bacterium responsible for the development of acne. The researchers studied bacteria collected from the follicles of acne patients and non-acne patients. At the same time, only P. acnes were found in the follicles of healthy people (without acne), but in the follicles of patients with acne, P. acnes, Staphylococcus epidermidis, and many other types of bacteria were found (in general, superficial skin samples of acne patients showed approximately 12–16 species of bacteria). It was not possible to detect previously uncultivated bacteria in acne patients. Thus, the identification of a mixed bacteria, and not P. acnes itself, is currently associated with acne.

Of great interest is the study of the association between the occurrence of sebum secretion and the expansion of P. acnes in the population of children 5.5–12 years old. In the studies conducted, the number of P. acnes on the skin tended to increase in children over 9 years of age, and the number of P. acnes in the nasal cavity significantly increased with age, but not with pubertal stages. The onset of sebum secretion and expansion of P. acnes occurred much earlier in children with acne than in children of the same age and pubertal stage without acne. This study confirmed that delaying sebum secretion and expansion of P. acnes in the skin until puberty may be a way to prevent acne and minimize its severity.

Correlation of skin pH level and stratum corneum enzyme activity

The relationship between the acidic mantle and resident flora has now been studied quite well. At the same time, some of the biological activity of the stratum corneum depends on variations in the acidity of the skin surface. The functional viability of the corneal layer requires the combined action of many enzymes that are produced in the granular layer and are mostly localized in the intercorneal space.

There are two main groups of enzymes: lipid modifiers and proteases, all of which play an important role in barrier homeostasis and corneocyte desquamation. Chymotryptic enzymes of the stratum corneum, phospholipase A2 and steroid sulfatase are neutral enzymes activated at pH 7; acidic enzymes (glucocerebrosidase, sphingomyelinase, acylcoenzyme A transferase) are activated at pH 5. A decrease in the pH gradient in the epidermis (with a neutral pH in the basal layer and an acidic pH in the stratum corneum) is a turning point in the activation and inhibition of the above enzymes.

Increased activity of the sebaceous glands, excessive growth of residual microflora, as well as hyperkeratosis are the main pathogenetic mechanisms in the development of acne vulgaris. Increasing the pH of the skin surface can affect not only the growth of microorganisms in the infundibular part (between the sebaceous gland and the surface of the epidermis), but also fine-tuning the local activity of enzymes in the stratum corneum. Thus, skin surface pH may be involved in the pathogenesis of acne.

Skin acidification and acne clinic

"Sour" cosmetic products

It is well known that superficial chemical peels (pH 2-3), accompanied by the use of acidic cosmetic products with a pH level below 4, help clear papulopustular acne without severe irritation - think about the long-known keratolytic effect of salicylic acid or alpha hydroxy acids. In this regard, it is interesting to determine whether acidic synthetic detergents (SDCs) will have a beneficial effect not only on the skin of healthy volunteers, but also on the skin of individuals prone to acne?

We have data from a study whose authors analyzed the effects of soap and acid syndet (a synthetic cleanser that does not contain alkali and soap) on the development of acne in individuals predisposed to this disease. In an open-label, comparative, controlled study, volunteers used either bar SMS or regular soap for 12 weeks. The duration of application of the cleanser was 1 minute every morning and every evening.

During the study, inflammatory and non-inflammatory acne lesions were counted, and the side effects of SMS (itching, redness, peeling) were also assessed. In the group of people who used soap, the average number of papules and pustules on the face increased from 14.6 to 15.3. In the group of people who used SMS, the number of acne elements decreased from 13.4 to 10.4 (p<0.0001).

Thus, experiments have shown that the use of acidic SMS when cleansing the skin can reduce the number of inflammatory acne, the skin reacts to such care more tolerantly. It should be noted that the effect of acidic detergents is explained precisely by their acidity, and not by their formulation. However, the ingredients in detergents cannot be ignored.

Acidifying microiontophoretic system

The work of German scientists using an acidifying microiontophoretic system seems to us to be a “pure” experiment studying the effect of skin acidification on the clinical manifestations of acne.

The study was carried out in one of the German clinics from October 2005 to March 2006. The acidity of the lesions was measured by applying a flat glass electrode of a pH meter directly to the surface of the acne element and equilibrated for 7 seconds. The skin pH level was recorded between 11 and 14 hours to prevent daily fluctuations. Papules and pustules were counted on both cheeks in fixed areas (8x8 cm).

To treat acne, a battery-operated microiontophoretic system (MIS) was used , which creates an electric field with a very weak current, which allows you to reduce the acidity in the desired area by 2 units (this system was originally developed for the treatment of herpes labialis in the early stages of development). The study's blinded crossover design included home use of the real microiontophoretic system and its mock (placebo). Patients used MFS at least 3 times a day directly on acne lesions. Volunteers were instructed not to use any other anti-acne medications during this treatment.

In total, 30 young people with phototypes I–II on the Fitzpatrick scale participated in the experiment, and were divided into 2 equal groups. The ratio of men to women was 1:1. Thus, neither gender nor age had an effect on the results. Participants also did not use any topical acid cleansers or used them once a day as needed. Thus, the influence of external factors that can change the pH of the lesions was minimized. However, home treatment was not completely ruled out. The anatomical part of the study was the cheeks and back, which are rich in sebaceous glands, since sebum secretion can actually affect the pH of the skin.

Progress of the study

In the first three weeks, patients in group A were treated with MFS, and patients in group B received placebo. After this period, specialists counted the number of acne elements in patients of both groups. The pH level was described according to the protocol of this crossover study. Over the next three weeks, patients in both groups changed treatment: group A received placebo, and group B received MFS. At the end of treatment, the number of acne lesions was again counted and the pH level was measured.

Before treatment, the pH of the patients' skin was 5.3–6.1. Group A had a pH of rashes of 5.66±0.24 and a total number of rashes of 22.5±0.1 papules and pustules on both cheeks. Group B had a skin acidity of 5.72±0.25, the total number of acne elements was 21.6±8.0 papules and pustules on both cheeks. Thus, before the start of the study, there was no statistical difference in the number of rashes and pH levels in both groups.

After three weeks of treatment, the number of rashes in group A (using MFS) decreased to 14.5±5.7 (p<0.01), the pH level decreased to 4.84±0.33. In group B, which used placebo, of course, no statistically significant changes occurred. Then the groups swapped devices.

After a full study lasting six weeks, the pH of the lesions in group A was 5.48 ± 0.19, the number of lesions was 19.9 ± 6.8. Well, in group B the number of rashes decreased from 20.5±8.0 to 13.6±6.0, (p<0.01), which was accompanied by a decrease in pH from 5.63±0.19 to 4.96 ±0.39 (p<0.001).

Thus, a statistically significant difference was recorded in the pH level (p<0.001) and the number of acne rashes (p<0.05) when comparing both groups at the end of the study (Table 1). The number of acne rashes decreased with daily use of MFS, which was accompanied by a decrease in skin pH in this area. The success of treatment depended on the duration of use (when treatment was stopped, the effect stopped and inflammatory elements appeared again). Treatment with MFS was accompanied by a slight burning sensation, but the use of a placebo device was not.

It is postulated that dry skin is associated with an increase in skin pH and may affect the bacterial flora. Staphylococcus aureus grows optimally at pH 7.5; Propionibacterium acnes – at pH 6.0–6.5. At the beginning of the study, the pH of acne lesions was 5.7 ± 0.2, which may enhance the growth of P. acnes. After MFS, the pH decreased to 4.84±0.33, and there were 14.5±5.7 lesions. This positive correlation of P. acnes abundance and skin pH may explain the clinical effect of MPS on acne. With an increase in skin surface pH, barriers are disrupted, which is accompanied by inflammatory reactions, so a decrease in pH in acne lesions may be pathogenetically more important in acne than suppression of bacterial growth. Thus, according to the results of a cross-sectional study, MFS may be an alternative treatment for inflammatory acne.

Table 1. Results of using MFS in patients with acne

Bottom line

Modern acne management includes non-ablative chemical peels . The cumulative effect of more than two superficial peels for acne does not damage the sebaceous secretion. Superficial chemoexfoliation does not significantly affect skin pH.

In modern reviews by leading acneologists, changes in skin acidity are not mentioned as one of the mechanisms for the development of acne, exacerbation of acne, or an increase in the severity of acne; acid therapy is also not reflected in recommendations for the treatment of acne. However, a simple conclusion follows from Table 1: a decrease in the pH level of the skin during acne is accompanied by a decrease in the number of rashes and vice versa. However, the standard therapy for inflammatory acne is still generally accepted with topical erythromycin, which has an alkaline pH (more than 7), and doctors recommend “soaking” with laundry soap. According to recent work on rational acne treatment, cleansing acne-affected skin should include acidic synthetic cleansers pH 5.5 rather than soaps. Moreover, the ingredients of such skin products should include nicotinamide, lactic acid, triethyl acetate/ethyl lineolate, plant extracts and prebiotics, which affect the pathogenesis of acne through various mechanisms. Biological methods are promising in this regard, namely the inclusion of prebiotics in the formulations of anti-acne drugs.

Of course, normalizing skin acidity using chemical, electrical or bacterial factors seems to be a gentler and more physiological method of treating acne than antibiotic therapy. However, this new direction requires study in different groups of patients, with different degrees of severity and forms of the disease.

First published: Les Nouvelles Esthetiques Ukraine, No. 3 (67), 2011