[Academic Presentation] The Role of Skin Barrier Repair in the Treatment of Acne

Acne is a chronic, recurrent inflammatory skin disorder that affects the hair follicles and sebaceous glands. With a high prevalence, it is a common dermatologic condition that significantly impacts appearance. In China, Zou Xi and colleagues measured the stratum corneum water content, lipid content, and transepidermal water loss (TEWL) in 80 patients with acne and found that sebum levels and TEWL values were higher, while stratum corneum water content was lower, compared with healthy controls, suggesting impairment of the skin barrier in acne. Meanwhile, Wu Yanyu and colleagues, studying 75 patients with mild to moderate acne, reported that TEWL at lesional sites was markedly higher than at non-lesional sites, whereas sebum saturation and sebum secretion rates were significantly lower; moreover, they observed a positive correlation between skin barrier dysfunction and the severity of acne lesions. Yamamoto et al. compared 36 patients with acne and 29… Studies of the cutaneous physiological functions in healthy controls have consistently demonstrated increased transepidermal water loss and elevated sebum secretion, accompanied by a reduction in stratum corneum hydration. Notably, in patients with acne, abnormal sebum secretion is not limited to an increase in quantity; it also involves alterations in the composition of sebum. Meyer reported that acne patients exhibit insufficient ceramide production, and since ceramides exert anti-inflammatory effects, their deficiency further exacerbates inflammatory responses. Furthermore, the impairment of skin barrier function varies across seasons: in summer, the primary feature is heightened sebum secretion, whereas in winter, transepidermal water loss becomes more pronounced.

Both domestic and international studies have demonstrated that the skin barrier in patients with acne is impaired to varying degrees, primarily characterized by increased transepidermal water loss, excessive sebum secretion, abnormal lipid composition, and reduced stratum corneum hydration. These findings provide a rationale for clinical management.

2.1 Effects of Common Medications on the Skin Barrier

2.1.1 Retinoids: Oral isotretinoin is currently the most effective medication for treating acne; however, it can affect the epidermal barrier in multiple ways. First, oral isotretinoin reduces desmosomes, leading to diminished intercellular connections and increased skin fragility, while also promoting epidermal turnover. Studies have shown that oral isotretinoin increases transepidermal water loss (TEWL) in a dose‑dependent manner. Its effects on cutaneous sebum production are even more pronounced: a reduction in skin lipid levels is typically observed after one month of treatment and persists with continued therapy. Four to five months after treatment cessation, sebum levels gradually return to pre‑treatment levels. Topical isotretinoin elicits treatment‑related cutaneous reactions similar to those observed with oral isotretinoin; topical retinoids may also cause burning, stinging, pruritus, erythema, and dryness, accompanied by increases in skin hydration and transepidermal water loss (TEWL).

2.1.2 Benzoyl Peroxide Benzoyl peroxide is one of the most important topical agents for treating acne, exhibiting antibacterial activity against Cutibacterium acnes, anti-inflammatory effects, and keratolytic properties, thereby providing therapeutic benefits for both inflammatory lesions and comedones. However, clinical experience has shown that some patients may develop intolerance reactions, such as stinging and erythema. Studies indicate that benzoyl peroxide can induce lipid peroxidation in the stratum corneum, altering the normal lipid composition of this layer and compromising the epidermal barrier. Furthermore, benzoyl peroxide can oxidize keratins, including keratin 1 and keratin 10, leading to a reduction in the thickness of the epidermal stratum corneum and increasing skin sensitivity. Repeated application of benzoyl peroxide significantly elevates transepidermal water loss (TEWL).

2.1.3 Antibiotics: Oral administration of minocycline, doxycycline, and similar agents has little impact on skin barrier function, whereas topical antimicrobial agents primarily affect the microbial flora. Topical antimicrobials may promote colonization by Staphylococcus epidermidis.

2.2 Topical Cleansers and the Epidermal Barrier

There are many types of detergents, which can be broadly classified into four categories: soaps, synthetic detergents, antibacterial soaps, and soap-free detergents.

2.2.1 Soaps Soaps are typically long-chain fatty acid alkali salts formed through the saponification of long-chain fatty acids with an alkali, and their pH is often greater than 7. Their advantages include strong cleansing power, enabling efficient removal of dirt and sebum from the skin’s surface. However, precisely because of this potent cleansing action, soaps can also strip the skin of its natural lipids and proteins, enhance the transcutaneous absorption of topical medications, and trigger irritant reactions. Moreover, soaps can raise the skin’s pH, increase transepidermal water loss, lead to dryness and scaling, and further promote inflammation. Consequently, soap‑based formulations are not suitable for facial cleansing. Antibacterial soaps, such as Dial, incorporate antimicrobial agents into the soap base. Nevertheless, these products are also unsuitable for facial cleansing in patients with acne, since they primarily target surface bacteria—mainly aerobic Gram‑positive organisms—whereas Cutibacterium acnes resides within hair follicles and sebaceous glands. Standard antibacterial agents cannot penetrate these deeper sites, and their efficacy against anaerobic bacteria is limited.

2.2.2 Cleansers Synthetic cleansers are formulated by adding other ingredients to traditional soap; compared with conventional soaps, their pH typically ranges from 5.5 to 7.0, closely matching the skin’s natural pH. In addition to effective cleansing, synthetic cleansers cause less removal of the skin’s native proteins and lipids, resulting in reduced feelings of tightness and dryness after use. Soap-free cleansers are currently among the gentlest products available on the market. These formulations are usually neutral to mildly acidic and do not contain soap, colorants, fragrances, salicylic acid, or other irritants; upon application, they leave a thin, moisturizing film on the skin’s surface. Previous studies have demonstrated that soap-free cleansers can be beneficial for sensitive skin conditions such as rosacea and atopic dermatitis, and recent reports also suggest their utility in the management of acne.

Draelos et al. evaluated the efficacy of Cetaphil Gentle Skin Cleanser in treating mild acne. The researchers enrolled 30 patients aged 18 to 50 with stable, mild acne and instructed them to use the cleanser twice daily without any concomitant pharmacologic therapy. Regarding the skin barrier, Two weeks later, the patients’ transepidermal water loss (TEWL) showed a slight increase, though the difference was not statistically significant, while stratum corneum hydration decreased significantly. The cleanser had no effect on sebum secretion. With respect to skin lesions, both the number of blackheads and the severity of acne were significantly reduced after two weeks of use. The study did not identify any irritation or intolerance. In another study, Subramanyan compared the efficacy and adverse effects of two cleansers when used in combination with benzoyl peroxide gel or adapalene gel. The results indicated that, compared with soap‑based cleansers, patients using mild‑formula cleansers experienced fewer instances of erythema, desquamation, burning, and scaling; moreover, in terms of lesion clearance, those using the mild cleanser exhibited a more pronounced reduction in acne severity scores. Therefore, in the treatment of acne, synthetic or soap‑free cleansers may be preferred.