'Bath additives don't work - basically you're pouring stuff down the plughole,' said Dr Miriam Santer, a GP and associate professor at Southampton University in primary care research, who led the BATHE study.
To determine the clinical and cost effectiveness of emollient bath additives, Dr Santer and colleagues recruited 483 children aged 1—11 years diagnosed with eczema from 96 general practices in England and Wales.
Participants were randomly assigned to receive prescriptions for bath additives or not, for 1 year. Both groups continued with standard eczema management, including leave-on emollients.
Eczema control was measured weekly for 16 weeks using the patient-oriented eczema measure (POEM), with scores of 0-7 indicating mild eczema and scores of 8—16 and 17—28 indicating moderate and severe symptoms, respectively.
No significant difference
The researchers found that mean POEM scores over the 16-week period were not significantly difference between the children who had emollient added to their baths and those who did not (7.5 vs 8.4).
After controlling for baseline severity and confounders (such as ethnicity and topical corticosteroid use) and allowing for clustering of participants within centres and responses within participants over time, POEM scores in the no bath additives group were 0.41 points higher than in the bath additives group (95% CI −0.27 to 1.10), below the minimal clinically important difference of 3 points.
There were also no significant differences between the groups for additional measures, including eczema severity over 1 year, the number of eczema flare-ups, quality of life, cost-effectiveness and adverse effects.
Dr Martin Ward Platt, a consultant paediatrician at the Royal Victoria Infirmary in Newcastle, said the trial's findings suggested NHS money should be spent on other treatments.
'That doesn't mean they [bath additives] shouldn't be available on sale for people who want to give them a try or use them out of personal preference, but the notion that one should prescribe them and spend public money on them is heavily undermined,' he said.
'There's a good case now to not have these on prescription and use the money elsewhere.'
Prescribing of bath additives in England costs the NHS more than £23 million annually.