I'm an avid watcher of the food network show, Good Eats, which focuses
on the science of cooking.  From watching it, I know why soaking my
turkey in saltwater makes it juicier.  (Osmosis, or diffusion.)

I'm also interested in the science of lotion, because I've got pretty
dry skin.  There are so many lotions on the market, each with special
ingredients, each claiming to be the best.  But what really matters,
lotion-wise?

Do lotions work by osmosis/diffusion, meaning that thicker or maybe
saltier lotions cause our skin to become turgid or flaccid?  Is
osmoregulation involved in the process?
Or is lotion all about adding oils, fats or lipids to the surface of
the skin to prevent water from evaporating away?
Do those fancy ingredients - oatmeal, alpha hydroxy acid, citrus
extract, seaweed, aloe - really help?  And what the hell is jojoba?

the bottom line question is: how does lotion work?  

In your answer, it's ok to use fancy words like "isotonic" if you
must, but please explain them.  In preparing the question, I did three
minutes or so of research, and ended up using words I understand in
this moment but will have forgotten by the time you answer. :)  But an
outstanding answer would be written at about an eighth-grade level.

I know what you mean about knowing something for the moment!!

I don't have a full answer for you but these are a few things I
consider when dealing with "lotions" by which I guess you mean
anything you put on your skin to handle dryness.
   1.  A quote from Dr. Sherry Rogers...IF IT IS IN THE AIR OR ON YOUR
SKIN IT IS IN YOUR BLOOD.  This tells you that whatever chemicals
listed on the ingredients will go thru your skin into your blood.  So,
I figure if it is going into our blood it should be something we can
eat (well, almost anyway).  Lots of times food oils are also full of
chemicals which are used first to extract the oil and more chemicals
to refine it...so just because we eat it does not mean it is pure.  I
trust the SPECTRUM brand to make chemical free, quality oils for
eating and for skin.  The oil I currently use on my skin is REFINED
AVOCADO oil by Spectrum...good for high heat cooking and for your
skin!  It soaks in and the shinyness goes away, and you can wipe it
with a towel to remove the excess. It is expensive if you are going to
use it for cooking but inexpensive for your skin as it lasts a long
time.  I pour some in a little eye-dropper bottle and use it from
there, keeping the rest in the refrigerator.  Very convenient but not
every store carries it.

      2.  The company I know of that is most committed to making
chemical-free body products is
Terressentials...http://www.terressentials.com/   They have very nice
people working there and would probably help you answer your
questions.

      3.  Other brand names that are acceptable are Weleda and Burt's
Bees.  Some companies profess to be "all natural" yet when you read
the ingredients they are far from it.

      2.  I happen to be allergic to jojoba oil but here is a quote
about what it is....Made from the bean of an evergreen bush native to
the Southwest. Closely resembles skin?s natural oils; contains protein
and minerals, and is good for all skin types, to soothe, soften,
nourish and protect. Jojoba oil is light and easily absorbed; helps
prevent stretch marks....Sooooo, it is a matter of personal trial and
error when selecting lotions.

     3.  I read a whole booklet on Aloe and bought a bottle of the gel
and tried it for dry skin but was not satisfied.  However, when
traveling in the tropics I cut the huge aloe leaves and skinned them
and used them on sunburn and it worked like magic.  Once again you can
experiment.

Happy days,

katten-ga, I don't normally like to advertise for big corporations;
they don't need it.  But, in this case, it's unavoidable.  Try Quench
by Olay.  At first, it feels like any other lotion.  After a few
minutes, it dries and leaves a smooth, non-greasy surface.  It's
effects last for more than a day.  Bear in mind that the one authoring
this note is a middle-aged man!

For more on this, visit the http://www.epinions.com website.  There
are other similar opinions on this product.

Lotion works by holding in moisture. This is why it works best after
you bathe. Lotion can't really *add* moisture to your skin; it just
retains it.

Kriswrite

Na-Pca by Twinlabs beats everything hands down because it replaces
what is missing so your skin is dry. And its inexpensive to make and
buy.