To anyone who has not studied science or chemistry or even those of us who have but have forgotten, trying to explain what pH is to someone who doesn’t know can be quite tricky. The inevitable question of what the ‘p’ in ‘pH’ stands for occurs and Doctor Google and Wikipaedia aren’t much help!
Anyway, a study in a recent edition of the British Journal of Dermatology looked at the effect of a low pH cream on aged skin.
[Angelova-Fischer I, Fischer T, Abels C et al. Accelerated barrier recovery and enhancement of the barrier integrity and properties by topical application of a pH 4 vs. a pH 5.8 water-in-oil emulsion in aged skin. Br J Dermatol 2018;179:471-77.]
Why aged skin?
Aged skin has an increased skin-surface pH and this together with decreased buffering capacity (ability to limit changes in pH when an acid or an alkali is added) leads to poor barrier function, delayed barrier recovery, dryness and scaling of the skin amongst others.
Why were they looking at lowering the pH?
Every organ and system in our body has a defined and tightly regulated pH. The stomach classically has a highly acidic pH (pH 1-1.5), whereas the lung has a neutral pH (pH 7.0) and the blood is slightly alkaline (pH 7.35-7.45).
Traditionally, facial cleansers and leave on products have been adjusted to have a pH around 5.5. The normal pH of the skin on most of the body is now thought to be acidic, in the range of pH 4.1- 5.8, the mean pH being 4.9.
[Proksch E. Lowering skin pH: improved barrier function, anti-ageing and beyond. Br J Dermatol 2018;179:254-5.]
What happens if the pH changes?
Diseases can lead to changes in pH and changes in pH can lead to disease. In relation to the skin, the pH can regulate barrier function, differentiation of skin cells, enzyme function and buffering capacity of the skin.
What did they do in the study?
They examined whether a water-in-oil topical application with a pH of 4 compared to a product with a pH of 5.8 improved skin barrier integrity and recovery in healthy female and male volunteers aged 60-85 years.
They looked at barrier integrity in 28 volunteers aged 60-78 years after sequential tape stripping to the left and right forearms. They looked at barrier recovery in 10 volunteers aged 60-72 years after application of acetone wiped 10 times to the skin of the left and right forearms.
What did they find?
The researchers found that the preparation adjusted to pH 4 reduced the pH of the skin and reduced water loss across the skin after application of acetone and after sequential tape stripping compared with the pH 5.8 formulation. There was reduced scaliness and roughness of the skin with both formulations but it was more pronounced in the ph4 formulation-treated area.
How does a decreased skin pH work?
It is thought to be something to do with enzymes in the skin, so called serine proteases whose activities are dependent on the pH of the skin, with upregulation causing scaling and roughness.
So where to from here?
Acidic preparations are already in use in the treatment of acne. More studies are needed to see if other skin conditions in which there is a disrupted skin barrier such as eczema or psoriasis will also benefit from pH targeted leave-on formulations.
[Proksch E. Lowering skin pH: improved barrier function, anti-ageing and beyond. Br J Dermatol 2018;179:254-5.]
Kind regards,
Sandy
Dr Sandy Flann, Consultant Dermatologist.
