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How long a moisturizer should maintain moisture in skin
Hello every bodyIs there any standard to show that how long a moisturizing cream should maintain moisture in skin? -
9 Replies
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As long as your consumers want it to.
When I worked on the St. Ives brand people were impressed with the claim “24 hour moisturization”
Realistically, a few hours is all you can expect.
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Thank you Perry.
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Does this mean when one applies petrolatum at night and washes it off in the morning: the skin will be back to baseline at 12:00 (I’m not sure about TEWL benefits longevity)?
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@luukheum - there are way too many variables to make an assertion like that. When I was working on the St. Ives 24 hr lotion we set up the following test.
1. Take baseline readings for TEWL (skin conductance actually)
2. Apply lotion then take readings after 10 min. Levels increase
3. Take readings throughout the day with subjects who stayed in a controlled environment room (humidity & temp).
4. Take readings the next day to see if TEWL was higher than baseline. For the 24 hour lotion it was, although only slightly.But under real life conditions, since skin moisturization depends so heavily on atmospheric & biologic conditions, it would be tough to say exactly how long you’d have measurable moisturization.
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Based on your experience on the St. Ives, is this a good assumption:
“if the lotion ads 100% TEWL, we should expect 25% of added TEWl to retain after 6 hours? (in controlled environment)?” or should be something like 50%?
@Perry -
No, that’s not a good assumption. TEWL measurements are highly variable. It can be 50% or 25% or 5%. It really depends on too many unknown factors. Air flow, skin movement, genetics…etc.
The reality is that this science is complicated and not very well understood. The genetic variability of people’s skin makes it difficult to predict.
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“But under real life conditions, since skin moisturization depends so heavily on atmospheric & biologic conditions, it would be tough to say exactly how long you’d have measurable moisturization.”
Would an humidifier in your bedroom be beneficial to skin? If so at what setting? How will this compare to moisturizing creams? -
EDIT: probably not something you want to do, see link. http://www.nytimes.com/1988/12/22/us/health-personal-health.html?pagewanted=1
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humidifiers work, when your environment is artificially dry (low RH); either due to AC (or winter), or to heated air. old people typically encounter this, which is usually accompanied either with sinus problems, or dry itchy skin.
usually the counter is either to install some sort of humidifier, or have them (in cases of skin dryness) use a humectant with a lot of water, or barrier cream (after the shower).
the problem with humidifiers, is that:
* a lot of the low end ones, are problematic from a sanitary perspective. particularly the ultrasonics, and cold-steam.
* you don’t want too much humidity, because then yeast, mold flairs up - the idea is to correct the defect, not turn the air into a swamp
* hot steam heats up the room, in summer (which is usually counter to why the air is arid in the first place i.e. cooling).
* humidifiers, in winter, lower the temperature (as they vapors hit the condensation point, they pull heat from the room, and also, high humidity air increases heat loss).…use of creams (moisturizers) don’t work long-term; the best is a barrier cream on fully hydrated skin. you can spot treat problems where there is a spike in heat (either drying out directly, or through extended use of AC), but the ultimate solution is to fix the problem (humidity of the air).
@perry
> 3. Take readings throughout the day with subjects who stayed in a controlled environment room (humidity & temp).
> 4. Take readings the next day to see if TEWL was higher than baseline. For the 24 hour lotion it was, although only slightly.TEWL readings using an evapirometer? I was reading a paper that studied the dynamics of TEWL (water loss), and they suggested that modeled TEWL loss, provided a better way of looking at how it was happening, due to nonlinear effects of moisture being pulled from the skin. i.e. rapid water loss, begets rapid water loss, until the system equilibriates and you get this slow decline of TEWL. But I think they indicated something like 50% decrease in a minute.
https://onlinelibrary.wiley.com/doi/full/10.1034/j.1600-0846.2002.10342.x
Methods/Results: The model, which is based on general results and methods of transport phenomena, has been calibrated and validated by experimental tests, in vivo, with the use of an evaporimeter. Both the theoretical model and the experimental results show that the release of excess water that accumulates in the skin following an occlusion, is a fast transient phenomenon, which has a characteristic time of the order of minutes (the initial decay is very rapid indeed, in less than a minute the TEWL value may decrease by more than 50%). On the other hand, the characteristic measuring time of the evaporimeter may be as large as 30 s. Therefore, as shown in the paper, the use of the evaporimeter for measuring the initial values of TEWL upon immediate removal of the occlusion is not reliable. When a transient phenomenon cannot be fully described by a measuring device that has an initial characteristic response time of the order of the characteristic time of the phenomenon, a mathematical model, which describes the dynamics of the phenomenon must be developed. Then the measurements taken after the measuring device is stabilised may be extrapolated to the initial times by the use of the model, thus allowing a full quantitative description of the phenomenon vs. time. Finally, the experimental results show that a baby’s disposable diaper, when loaded with water, behaves like an impermeable occlusive cover on the skin.
Context of the search was related to a forum post, regarding silicones as a film-formed barrier preventing TEWL.
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