The most adjustable event of the day
You cannot change the sea temperature, the wind or the humidity. You can change every single variable of your shower, and most people change none of them.
There are four: how hot, how long, what you wash with, and what you wash. All four move in the same direction as your comfort, which is the problem, because after ninety minutes in cold water your comfort points at very hot, very long, plenty of soap, everywhere.
Temperature does the most
Warm water affects the barrier by two routes.
First, the lipid sheets between corneocytes are physical structures whose components are more mobile at higher temperatures. Warm water removes more of them for the same contact time and the same surfactant, particularly in combination with a detergent whose job is to lift lipid into water.
Second, warm skin has a higher vapour pressure at its surface, so water loss is higher while it is warm and for a while afterwards. Getting out of a hot shower into a heated bathroom is a period of rapid loss from a layer that has just been stripped.
The practical version is not cold showers, which most people will not do and which have their own literature we are not going to wade into. It is one notch cooler than feels good, which is achievable and which is most of the benefit.
Length does the second most
Contact time multiplies everything. A long shower gives more swelling of the outer cells, more leaching of what holds water inside them, and more lipid removal.
It is also where the hidden immersion sits. People count a session in the sea as their immersion for the day and do not count the fifteen minutes standing under hot fresh water afterwards, which by the mechanisms in the article comparing waters is the more aggressive of the two per minute.
What you wash, and what you only rinse
Here is the change that costs nothing and that almost nobody makes: stop applying detergent to your whole body.
Salt rinses off with water. Sand rinses off with water. Most of what is on you after a session does not require a surfactant. The parts of the body that need washing are a short list, everyone knows what it is, and it does not include the shins, the forearms, the back or the chest on most days.
Every site you apply a wash to is a site where intercellular lipid is being lifted into water and rinsed away. Reducing the area is a direct reduction in the total insult and it takes no effort at all.
| Variable | What it changes | The direction that helps |
|---|---|---|
| Temperature | Lipid mobility and post shower loss from warm skin | One notch cooler than feels good |
| Duration | Multiplies swelling, leaching and lipid removal | Several minutes shorter |
| Area treated with detergent | Total lipid removed across the body | The short list only, rinse the rest |
| The wash itself | pH and surfactant strength | Near skin pH, milder system, no fragrance |
| What happens after | Mechanical removal from a softened layer | Blot, then apply while still damp |
Ordering framework written by this publication from general skin physiology. It is not a measurement, it is not taken from any study, and no number in it is a reading.
Choosing a wash by function
We describe ingredient classes by function and never by brand, and we do not recommend products. What can be said usefully about a wash is limited to properties.
A wash formulated near the pH of skin does not add the alkalinity insult described in the article on surface pH. Traditional soap, by its chemistry, is alkaline.
Milder surfactant systems remove less lipid for the same cleaning. The label rarely tells you which system is used, and words such as gentle and natural carry no information about it.
Fragrance is a common cause of contact allergy and adds nothing to cleaning. What fragrance free actually means, and what it does not, is covered in its own article.
Beyond those three properties, the choice matters less than the temperature, the duration and the area, which is a conclusion that suits nobody selling anything.
The two minutes after
The shower does not end when the water stops.
Blot rather than rub. The layer is softened, its bonds are strained, and a brisk towel removes cells with very little effort. This is worth more than any product decision you will make that day.
Apply while still slightly damp. An occlusive or emollient layer over damp skin holds water in the layer rather than sealing a dry one.
Do not stand about in a bathroom with an extractor fan running on wet skin, which is a small local wind exposure at the moment of maximum loss.
On cold showers
Cold water immersion has a substantial popular literature about which we take no position, since it concerns claims about recovery, mood and adaptation that are outside our subject and outside our competence.
From a barrier point of view, cooler water removes less lipid, causes less swelling and leaves skin at a lower temperature with lower loss afterwards. That is the whole of what we are prepared to say. If you want the physiological claims assessed, the place to look is the research literature and not a skin publication.