( BBC ) - Bath products to help ease the skin inflammation caused by allergic eczema may not be worth the amount of money the NHS spends on them, a study says.
There is no clinical evidence these emollients work, nor any consensus of medical opinion, researchers writing in Drug and Therapeutics Bulletin contend.
They calculate the NHS is spending Ј16m per year on emollients, which can cost as much as 70p per bath.
Allergic eczema is a condition which most commonly affects children.
Applying specialist ointments and lotions straight onto the skin may be effective, the paper concedes
Although there is little published evidence on whether topical treatments work, it says "long clinical experience has suggested that emollients applied directly to the skin are effective and safe".
But the same cannot be said for bath water products, the researchers said, calling for a proper evaluation of their use.
Bath emollients are thought to be an easier way of applying the treatment to a large skin surface area and they are also thought to trap moisture into the skin.
But the researchers said there was nothing to suggest they did this, and that they may even have undesirable effects, such as accidents caused by a slippery bath.
The National Eczema Society accused the researchers of ignoring "the extensive evidence from those patients and parents who find the use of bath emollients both soothing and extremely beneficial".
"Patients who use emollient bath oils to manage their eczema in this way can reduce the need for more specialized and expensive treatments," said its chief executive, Margaret Cox.
Colin Holden, president of the British Association of Dermatologists, which recommends the use of emollient baths, said "an absence of evidence does not equate with evidence of absence".
"Emollient therapy has been a major therapy for eczema for centuries and all trials done in eczema have allowed bath oils.
"Our guidelines are based on current practice, which is derived from research, clinical experience, and patient responses."