Eczema is a very common skin conditions that affects about  One common treatment is the use of emollient bath additives that are supposed to help moisturize the skin. However, a recent  has questioned whether these products offer any advantage.
Eczema can be very debilitating, especially to children. It is a chronic inflammatory condition that causes dryness, redness and itchiness of the skin. Treating this condition can be very difficult. The basic approach is to avoid things that dry out the skin like excessive bathing, low humidity, hot weather, emotional stress, and substances that can irritate the skin. Using moisturizers is also key to reducing skin dryness and topical steroid creams are used to treat the inflammation. When these fail, oral medications and phototherapy with UV light is sometimes used.
Often added to the treatment regimen are emollient bath additives. Emollients, as the name suggests, are ointments and creams that contain very little water. They act by coating the skin and providing a protective barrier that protects the skin against irritants. They also prevent moisture from escaping. Lotions, by contrast, have more water than emollients and are less effective at treating skin dryness. As most people know, water actually makes dry skin worse.
Emollients can be used a number of different ways. The first option is to apply them directly to the skin, usually after a shower or bath, to keep skin from drying out and leave the emollient in place. However, some people use them as soap substitutes since some soap products can be irritating to the skin. Finally some people use emollient bath additives, basically oils or emulsifiers, that are poured into the bathwater with the idea that they would leave an oily protective film on the skin.
Emollients that are applied directly to the skin have evidence to support their use. Research has been done on this issue and a  found that they did offer a benefit to patients. But emollients added to bath water are a different story. There was no good evidence that they actually worked, especially if you were already applying emollients to your skin, as most people did. Given that they are widely prescribed in the UK, researchers set out to test if they actually offered any benefit.
The BATHE trial randomized 483 UK children aged 1 to 11 to either use emollient bath additives plus usual care or usual care alone (which involved using emollients applied to the skin and continuing all their regular treatments). At 1 year of follow-up, eczema symptoms as reported by patients did not differ between the two groups. Eczema severity and the number of eczema exacerbations also showed no difference.
There was some suggestion of a small benefit in children under 5 years old or in those who bathed frequently (five or more times per week). However, these types of sub-group analyses have to be . Cut up the data many different ways and you can sometimes get . In one famous example, the , one of the early trials showing a benefit to giving aspirin to patients having a heart attack, showed that one subgroup of patients actually did not benefit from aspirin. That sub-group was patients born under the zodiac sign of Gemini and Libra. The authors highlighted that all these subgroup analyses should be taken less as evidence about who benefits than as evidence that such analyses are potentially misleading.”
Nevertheless, the BATHE trial was overall negative and raised the question of whether we are “wasting millions on an ineffective treatment,” as an  asked. Given the results of the trial, it seems likely that the money spent on emollients that are poured into the bathwater could be better spent on other aspects of care. In the UK this money amounts to approximately £23 million (roughly $40 million CAD) and represents a considerable expense for the public. Given the rising costs of healthcare, testing and evaluating which therapies don’t actually work, is not only good science, it’s also good economics.
