What's the science behind bath oils? by Dr. Christopher Labos
This blog contribution is by Dr. Christopher Labos - a timely article with winter dry skin in mind, do bath oils actually help as much as marketers would have you believe? Thank you Christopher for contributing to The Eco Well blog! Stay tuned! From here on out, we will be regularly featuring educational posts from scientists in and around the cosmetics space. Our goal is to create a knowledge-sharing platform, accessible to anyone :).
It is one of the great ironies of life that water dries out your skin. So a daily bath or shower can make dry skin worse. It’s worse when you have atopic dermatitis, the inflammatory, itchy skin disease that’s common in children and usually better known as eczema.
The main treatment for eczema is first to avoid things that irritate the skin like hot dry weather, stress, infections, things that can irritate the skin and of course water, i.e. bathing or showering too much. The next thing is to keep skin hydrated. Moisturizers are key here and there is a fair amount of research on this issue. A Cochrane Review found that emollients and moisturizers used for eczema did offer a benefit to patients. There are many different types of emollients and they can be sold as creams, ointments or lotions.
Creams and ointments contain less to no water. They act by coating the skin and providing a protective barrier against irritants. They also prevent moisture from escaping. Lotions, by contrast, tend to have a higher water content than ointments and creams and are less effective at treating skin dryness. Another popular option is emollient bath additives that are poured into the bathwater with the idea that they would leave an oily protective film on the skin.
There is however no good evidence that emollient bath additives actually work, especially if you already use moisturizers on your skin regularly. They are however widely used so researchers in the UK set out to test them.
The BATHE trial randomized 483 UK children aged 1 to 11 into two groups. The first group was told to continue their usual routine (which was basically applying emollients to their skin and continuing all their regular medications if they took any), while the second group continued with their usual routine but added emollient bath additives. 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 viewed with caution. Cut up the data many different ways and you can sometimes get false positive results. In one famous example, the ISIS-2 trial, 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.”
The editorial that accompanied the study’s publication in the BMJ asked whether we are “wasting millions on an ineffective treatment.” In the UK this money amounts to approximately £23 million (roughly $40 million CAD) and represents a considerable public expense. It seems likely that the money spent on emollients that are poured into the bathwater could be better spent on other aspects of care. This isn’t just good science, it’s also good economics.
Dr. Christopher Labos
Dr. Christopher Labos is a cardiologist with a degree in epidemiology. He spends most of his time doing things that he doesn’t get paid for, like doing research, teaching, and podcasting - co-host of the science podcast The Body of Evidence. Occasionally, he finds time to practice as a cardiologist so he can pay his rent. He realizes that half of his research findings will be disproved in five years: he just doesn’t know which half. He is a freelance contributor for the Montreal Gazette and regularly appears on CJAD radio. To date, no one has recognized him on the street. You can find him on Twitter at @DrLabos.