The study suggests applying olive or sunflower oil to a newborn baby's skin delays the development of an important barrier function.
The study, led by the University of Manchester in the UK, is published in the journal Acta Dermato-Venereologica.
The finding goes against the advice normally given by many midwives, who recommend olive or sunflower oil for dry skin in young babies - despite there being few studies that support this, say the researchers, who highlight instead that changes to baby skin care have been linked to a dramatic rise in eczema in recent decades.
In the 1940s, the rate of eczema in children aged 5-15 was around 5%. Today it is around 30%.
For the pilot study, the team recruited 115 newborns at Manchester's Saint Mary's Hospital and put them in three groups: olive oil, sunflower oil and no oil.
The babies in the oil groups had a few drops of oil applied to their skin twice a day for 28 days.
At the end of the 4 weeks, the researchers examined the lipid lamellae structure of the skin of the babies in all three groups.
The lipid lamellae (literally fatty plates or flakes) are in the stratum corneum - the outermost layer of the skin - and play an important role in the vital barrier function of the skin.
Oils may delay lipid lamellae development in the skin barrier
The researchers found that in the two oil groups, the development of the lipid lamellae in the newborns' skin was delayed, compared with the no oil group.
First author Dr. Alison Cooke, a lecturer in midwifery at Manchester, explains the role of lipid lamellae in protecting the skin:
"If the skin barrier function is a wall with bricks made of cells, then the lipid lamellae is the mortar that holds it together. If it isn't developed enough, then cracks appear which let water out and foreign bodies through."
She suggests that applying oil to a newborn baby's skin prevents the "mortar" from developing as quickly as normal, and this could be a reason for the development of conditions like eczema.
While the results showed that the newborn babies that had oil applied to their skin did have better hydrated skin, the researchers nevertheless suggest this may not be a good enough reason to risk the possible effect on the barrier - at least not until more research carries out a fuller exploration.
The researchers note that while there is no national guideline on skin care in newborns in the UK, some studies from South Asia suggest sunflower oil can protect the skin from microbial infection in preterm babies born in developing countries.
In the meantime, they say they cannot recommend the use of either sunflower or olive oil on the skin of healthy newborns in the UK, as Dr. Cooke explains:
"We need to do more research on this issue with different oils and also study possible links to eczema, but what is clear is that the current advice given to parents is not based on any evidence, and until this is forthcoming, the use of these two oils on newborn baby skin should be avoided."
Meanwhile, Medical News Today learned from another recently published study that skin cells can flip between maintenance and healing states. Researchers discovered this from observing the cells in high-definition movies.