Novel zinc lactobionate emollient maintains acidic skin surface and improves skin barrier in atopic dermatitis patients

There is a variation in skin surface pH (pHSS) between individuals and is impacted by gender, skin pathology, age and exposure to environmental factors such as treatment usage and washing regimes. pHSS is acidic in healthy individuals, ranging from 4.1 to 5.8. Maintenance of an acidic stratum corneum (SC) pH (pHSC) is crucial to skin homeostasis.

The researchers showed that a new zinc lactobionate formulation (pH 4.0) containing skin lipids helps maintain an optimum pH and strengthen the skin barrier compared with a vehicle control (pH 7.0). Treatment with the new formulation also led to a more hydrated SC and reduced sensitivity to irritation.

The regular application of the test cream used in the study resulted in improved skin barrier function and a physiologically relevant reduction in pH compared with a vehicle. Decreased protease activity and improved hydration suggest that the use of a skincare product containing humectants and physiologically relevant lipids at pH 4 can lead to good skin health and potentially improve disease control for AD patients.

The buffering capacity and pH of a topical preparation are likely to significantly affect the biophysical effects of that treatment. Therefore, the researchers suggest considering the pH of preparation when formulating and prescribing treatments to address skin conditions with a known barrier impairment.

The skin of patients with AD is characterized by elevated pH. As a central homeostatic regulator, an increased pH suppresses lipid processing and accelerates desquamation, leading to diminished skin barrier function. There is a requirement for skincare products to effectively moisturise the skin at a more favourable pH to support barrier function, maintain skin health, and alleviate dryness.

Against the above background, Paul V. Andrew, The University of Sheffield, Beech Hill Road, Sheffield, UK, and colleagues aimed to determine whether a novel zinc lactobionate emollient cream can strengthen the skin barrier by lowering skin surface pH.

For this purpose, they undertook a double-blind, forearm-controlled cohort study in patients with atopic dermatitis. Participants applied the test cream to one forearm and a vehicle cream, was applied to another (randomised allocation) twice daily for 56 days. The primary outcomes, skin surface pH and barrier function were assessed at baseline and after 28 days and 56 days of treatment, amongst other tests.

Twenty-three adults with atopic dermatitis completed the study.

Based on the study, the following inferences were made:

• During and after treatment, a sustained difference in skin surface pH was observed between areas treated with the test cream and vehicle (4.50 ± 0.38 versus 5.25 ± 0.54, respectively). This was associated with significantly reduced transepidermal water loss (TEWL) in the test cream-treated areas compared with control (9.71 ± 2.47 versus 11.20 ± 3.62 g/m2/h).
• Improvements in skin barrier integrity, skin sensitivity to sodium lauryl sulphate, skin hydration, and chymotrypsin-like protease activity were all observed at sites treated with the test cream compared with the control.

'The majority of clinical studies which have manipulated skin pH using an emollient have targeted a cohort of older participants to address the xerosis and increase in pH that occurs in aged populations," the researchers wrote. "This study offers insight into the acidifying emollient use in AD patients."

Reference:

Andrew, P.V., Pinnock, A., Poyner, A. et al. Maintenance of an Acidic Skin Surface with a Novel Zinc Lactobionate Emollient Preparation Improves Skin Barrier Function in Patients with Atopic Dermatitis. Dermatol Ther (Heidelb) (2024). https://doi.org/10.1007/s13555-023-01084-x