Skin surface pH of males should be 5.5 and in a range of 5.4–6.0 for females12-14; Accordingly, the alteration of pH of skin is considered to be one of the causes of acne.13 The elevation of skin surface pH may be due to many factors, including an imbalance in the hormonal milieu leading to alteration of sebum quantity and quality.13
Skin Barrier Defect
Alterations in skin barrier function and integrity have been reported in acne-affected skin7, 16-18; however, it is unclear whether these alterations are a sequelae of the disease process or a predisposition to acne itself.8 Skin lipids from both sebum and epidermal cells, including the lamellar bodies, are crucial to a slightly acidic pH and moisture balance within the stratum corneum (SC).7,8,13 The structural and functional integrity of the SC is highly dependent on adequate water in the skin barrier.7,8,13,14,16,17
Sebum excretion rates were compared on the forehead of healthy male subjects without acne to those with mild–moderate facial acne.16 Trans-epidermal water loss (TEWL) level was higher, while the conductance value before the water sorptiondesorption test was lower in both mild and moderate acne groups compared to the control group.16 The hypothesis is that an impaired water barrier function caused by decreased amounts of ceramides may be responsible for comedo formation.16 Acne-affected skin had a much lower water retention rate and therefore had a much faster water decay.16 Since skin barrier dysfunction is accompanied by hyperkeratosis of the follicular epithelium, acne flares may occur.8,16,17
Statement 3: There is a paucity of research on the pathogenic role of pH in acne but there is an association with higher skin surface pH in patients with acne.
There have been few studies performed evaluating the pathogenic role of pH in acne; however, the association of acne with an elevated skin pH was shown in a prospective observational study measuring skin surface pH.13 Both the case group (mild-to-moderate acne [N = 200]) and control group (healthy individuals [N = 200]) were instructed to refrain from using cleansers and topical products on the face for 24 hours prior to the pH test.13 Also, the case group did not take any oral acne medication in the 3 months prior to the study. Of the case group, only 44 (22%) had a physiological skin surface pH (5.5 for males and 5.4–6.0 for females) compared to 186 (93%) in the control group.13 Of those with acne, 155 (77.5%) were found to have a statistically significant (χ2= 210.452 with 2 degrees of freedom; P<0.001) higher skin surface pH compared to 12 (6%) subjects in the control group.13 The mean (± standard deviation [SD]) skin surface pH in the case group was 6.35 (SD ± 1.30) compared to 5.09 (SD ± 0.39) in the control group, which was also statistically significant (P<0.001).13
Another comparative study addressed the question whether skin surface pH is different in those subjects with acne.18 Sebum excretion and skin surface pH, measured in five different areas of the face, were shown to be higher in patients with acne compared to healthy controls.18
Statement 4: Many skin care products and acne therapies disrupt skin barrier function, which potentially impact patient adherence and therapeutic outcomes.
Acne-affected skin has been shown to have an elevated pH compared to normal skin and may be more prone to irritation resulting from acne treatment.13,18 Many of the systemic and topical medications, such as retinoids, antibiotics, and benzoyl peroxide, are associated with skin-barrier alteration, causing irritation and dry skin conditions.19-22 These unwanted effects can reduce adherence to treatment and therapeutic outcomes.23-25 Over-the-counter non‐comedogenic cleansers and moisturizers have been successfully used to reduce skin irritation; however some of these products, such as those with a high pH, are shown to interfere with the efficacy of topical treatments.26,27
The panel stated that pH levels in acne cleansers are not always known; physicians prescribing topical acne treatments need to understand some cleansers will also irritate the skin, possibly leading to elevated pH and to acne exacerbation.27
Statement 5: Cleansers and moisturizers close to physiologic skin surface pH (4.0–6.0) improve skin barrier function and treatment tolerability, and should be part of the acne treatment regimen.
In acne-affected skin, elevated sebum excretion may trigger compensatory factors such as C. acnes proliferation, activation of the inflammasome, lesion development, irritation, and a disrupted skin barrier.23,24 By reducing inflammation, skin condition in acne may be improved.23,25-27 Cleansers and moisturizer use is one of the measures to reduce inflammation and to improve skin barrier function.22-27
The panel agreed maintaining an intact skin barrier is important to successful treatment of acne,22-28 and considered moisturizer use to be an important counterintuitive factor for treatment. However, they recognized that many physicians are confused about moisturizer use in acne. Cleansers and moisturizers support epidermal barrier repair in acne patients.22-27,29,30; studies have shown normalizing the skin surface pH reduces the inflammatory TH2 response and enhances barrier function recovery, thereby preventing epidermal hyperproliferation.17,23,28,29