Using moisturising cream to treat eczema could make the condition worse, it is claimed.
Research from Bath University shows that well-known high street-branded creams can aid skin irritation. Instead, sufferers of the painful skin condition should use oil-based treatments.
The study found that ointments such as aqueous cream BP reduces the thickness of healthy skin over a period of four weeks.
Originally used as a wash product, the cream is now the most widely prescribed moisturiser for the treatment of dry skin conditions.
It is used to moisturise the skin, improving flexibility and preventing cracking in the protective outer layer, called the stratum corneum.
However, the cream contains a detergent, called sodium lauryl sulphate (SLS), which can increase the permeability of the skin barrier and cause irritation.
The study found that when healthy volunteers applied the cream daily for four weeks, the thickness of the stratum corneum was reduced by more than 10 per cent.
The researchers anticipate that using this cream would have an even more dramatic effect on damaged skin such as that found in eczema.
Richard Guy, professor of pharmaceutical sciences at Bath, said: "The skin has a protective barrier layer of lipids, around one-eighth the thickness of a sheet of paper, that stops chemicals from getting into the body and keeps moisture in.
"SLS is a detergent used to mix oils into water-based moisturisation creams to give a nice creamy texture. It's also used widely in shower gels and other cosmetics. Our study has found that rubbing aqueous cream containing SLS into the skin thins this protective barrier, making the skin more susceptible to irritation by chemicals."
The university's research is published in the British Journal of Dermatology.