Did you know that petrolatum penetrates between the cells of the stratum corneum and sped up barrier recovery in a study?
A belief worth testing
Petroleum jelly is one of the oldest and most common products for dry or chapped skin. For a long time it was thought to work as an impermeable film on the surface, able to block evaporation and trap water under the skin.
If that were true, petroleum jelly should slow down the repair of the barrier after damage, as had been seen in experiments on mice with occlusive films. The researchers decided to test this in people.
How the study was done
In the study, published in 1992, the researchers disrupted the skin barrier of volunteers in a controlled way using acetone, a solvent that strips lipids from the skin. They then compared how the barrier recovered in areas treated with petroleum jelly and in untreated areas.
Using special staining and tracer techniques, they also looked for where the petroleum jelly ended up inside the stratum corneum, the outermost layer of the skin, and how it was arranged in relation to the structures between the cells.
What was observed
Contrary to expectations, petroleum jelly sped up the recovery of the barrier. The treated areas repaired faster than the areas left without product.
Petroleum jelly was found in the spaces between the cells at every level of the stratum corneum, where it took the place of the lipid structures between one cell and the next. According to the authors, petroleum jelly spreads throughout the stratum corneum and allows normal barrier recovery despite its occlusive properties.
How to read the result
This study is a fine example of research overturning an idea taken for granted. It dates from 1992, however, and the abstract does not say how many volunteers took part. The barrier damage was caused artificially, which is different from everyday dry skin.
The practical message is that a simple ingredient can behave in more complex ways than we think. Petroleum jelly remains a widely used product for dry or chapped areas. If the skin is broken, inflamed or not getting better, a dermatologist should recommend the right treatment.
This article is for information only. It does not replace the advice of a doctor or dermatologist, whom you should consult with any question about your skin.