Should we use bath emollients for atopic eczema?
BMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b4273 (Published 13 November 2009) Cite this as: BMJ 2009;339:b4273
- Andrea Tarr, associate editor,
- Ike Iheanacho, editor
- Correspondence to: I Iheanacho iiheanacho{at}bmjgroup.com
Regular topical application of an emollient cream or ointment is key in the management of patients with atopic eczema and is thought to help the skin maintain a defensive barrier effect, which is defective in atopic eczema.1 Support for such treatment comes from one (non-blinded) randomised controlled trial, which found that regular application of emollients direct to the skin reduced the amount of topical corticosteroid cream needed for atopic eczema in infants.2 Long clinical experience also suggests that directly applied emollients are safe and effective in atopic eczema.
People with atopic eczema are commonly also advised to use an emollient substitute for soap (such as aqueous cream or emulsifying ointment), as soap can irritate the skin (as can bubble bath preparations); patients are also often prescribed a bath emollient to add to their bath water.3 Bath emollients typically consist of liquid paraffin plus another emollient (usually wool fat or isopropyl myristate); a few also contain an antimicrobial drug.
Some prescribers recommend bath emollients to avoid use of bubble bath preparations. Some believe that using a bath emollient is an easy way to apply an emollient to a large area of skin, particularly for children, who may not cooperate with having topical emollients applied frequently. Also, some treatment guidelines argue that complete emollient therapy (a combination of creams, ointments, bath emollients, and soap substitutes) will provide maximal effect.4 Of note, the National Institute for Health and Clinical Excellence’s guideline on atopic eczema in children (applicable to England, Wales, and Northern Ireland) suggests the additional use of bath emollients for some children “to ensure that adequate amounts of emollient are absorbed into their skin.”5 These influences have prompted very common use of bath emollients for atopic eczema.
What is the evidence of the uncertainty?
We searched PubMed, the Cochrane Library, Clinical Evidence, and the Current Clinical Trials database to identify published and ongoing randomised controlled trials and systematic reviews that have assessed the efficacy of bath emollients in patients with atopic eczema. This search followed previous wide consultation among specialists, as well as drug companies, to identify relevant published evidence while preparing an article on bath emollients for the Drug and Therapeutics Bulletin.6
No published randomised controlled trials have specifically assessed the clinical efficacy of bath emollients in atopic eczema.7 8 Also, we are not aware of any longstanding clinical experience of benefit from bath emollients to match that for directly applied emollients. The quantities of emollient deposited on the skin during bathing are likely to be far lower than with directly applied emollients. These points highlight the weakness of the case for using bath emollients.
Additionally, we found no published evidence that “complete emollient therapy” has a “maximal effect.” Moreover, the unproved concept of “complete emollient therapy” has fostered assumptions that each of the individual components (including bath emollients) contributes to a worthwhile benefit, despite the absence of confirmatory data.
On current evidence, bath emollients could be offering little or no benefit. If so, people who use them in place of directly applied emollients are unknowingly receiving substandard emollient therapy.
Is ongoing research likely to provide relevant evidence?
Trials on the clinical efficacy of bath emollients in atopic eczema are feasible but no such studies seem to be in progress (www.controlled-trials.com/mrct/). The box outlines possible research that could be conducted. Such research might facilitate development of products that produce bubbles for young children to enjoy in the bath but do not irritate the skin and which can be bought over the counter; this would obviate the need to use bath emollients to fill this gap.
Recommendation for further research
Population: Adults and children with atopic eczema
Interventions and comparisons: Firstly, whether for someone using directly applied emollients the addition of a bath emollient to bath water offers clinically worthwhile benefit compared with having plain water baths using a suitable emollient as a soap substitute; secondly, how once-daily topical emollient plus bath emollient compares with twice-daily topical emollient
Outcome: The effects on the severity of eczema (not merely questionable surrogate markers such as short term changes in skin hydration and transepidermal water loss)
What should we do in the light of uncertainty?
Robust clinical trial data could reassure patients and prescribers that bath emollients are worth using for atopic eczema or, alternatively, show that spending by the NHS in the UK on these products (about £15.5m (€17m; $25.4m) in England alone in 20089) could be put to better use. In the absence of confirmatory data, no basis exists for asserting that patients who sucessfully apply emollients directly to the skin but do not also use bath emollients are using substandard treatment.
Notes
Cite this as: BMJ 2009;339:b4273
Footnotes
This is a series of occasional articles that highlights areas of practice where management lacks convincing supporting evidence. The series advisers are David Tovey, editor in chief, the Cochrane Library, and Charles Young, editor of BMJ Clinical Evidence and editor in chief, BMJ Point of Care. We welcome any suggestions for future articles (uncertainties.bmj{at}bmjgroup.com).
Contributors: II suggested the review topic. AT conducted the initial literature review, which was repeated for verification by II. AT prepared the first draft of the paper, which was revised by II, who is also the guarantor.
Competing interests: None declared.
Provenance and peer review: Commissioned; externally peer reviewed.