If water molecules are so smallwhy don't they go through skin pores?

[Mintaka]

I read that essential oils can go through the skin. I am told that there are more water molecules in just 10 drops of water than stars in the whole universe, so if they are so tiny, why don't they go through the skin membrane pores, which are perfectly visible under an optical microscope? You would think they would flood through.

Thank you

 

[Vanadium 50]

Why do you think they don't?

 

[256bits]

You would think they would flood through

Have you ever heard of a wine skin?
The old-old style was made from the skin of a domestic animal.
The water does not flood through so to speak, so there must be a reason why not.
Can you think of a reason, or a couple of them, why not.

 

[sophiecentaur]

Goretex is designed to let molecules of water through but the membrane is still impressively 'waterproof'. It could be easier, perhaps, to think in terms of a simple artificial structure rather than a biological one. Your skin pores are not just holes in the skin.

 

[Mintaka]

I see I have been showing my ignorance here. I suppose my question should have been : "Why do some medicines, poisons and pharmacceutical chemicals pass through into the bloodstream, but water molecules do not" ?

 

[klimatos]

I read that essential oils can go through the skin. I am told that there are more water molecules in just 10 drops of water than stars in the whole universe, so if they are so tiny, why don't they go through the skin membrane pores, which are perfectly visible under an optical microscope? You would think they would flood through.

Thank you

I believe that you will find that perspiration involves the passage of water molecules through the skin. I also think that you will find that skin pores are not simply openings in the skin, but are functioning portals that both permit and bar passage of both gases and fluids. The default position is closed, hence the past use of "wine skins".

 

[Mintaka]

I really appreciate your answers, but still no answer as to why chemicals like nicotine can pass into the bloodstream but water doesn't.

 

[sophiecentaur]

Why do you keep insisting that water cannot pass through the skin? Have you not seen what happens when you spend a long time laying in a bath of fresh water? The skin of your fingers becomes noticeably puffy because of osmosis. The same happens to all of your skin but it is not so visible although the skin feels different. Because the rate of diffusion depends upon the relative concentrations of molecules on either side, it is not surprising that the rate of passage of water is slow - you already have most of your tissue full of water.

 

[Mintaka]

Thanks for your reply, I understand that my skin is soaked and puffy, but the water (and soap too presumably) don't pass into the bloodstream, do they?

 

[davenn]

I really appreciate your answers, but still no answer as to why chemicals like nicotine can pass into the bloodstream but water doesn't.

But nicotine isn't entering the bloodstream via your skin pores
Its entering via processes occurring primarily in the lungs

You may also consider that because blood plasma is >90% water
there are obviously processes occurring in the body that allow water to
enter and make up a large % of your blood streamDave

 

[sophiecentaur]

Thanks for your reply, I understand that my skin is soaked and puffy, but the water (and soap too presumably) don't pass into the bloodstream, do they?

How do you 'know' that none of your bathwater gets into your bloodstream? How would you ever have been able to do a test for it? If it gets into your skin, why wouldn't you expect it to get as far as your blood stream? Having established that large molecules like Nicotine get through your skin and the bathwater effect, how can you still believe that water doesn't get into your blood stream. What would you think would be the effect of a few grams of water getting in through your skin? Is it likely to cause any detectable reaction? Otoh, a gram of Nicotine would kill you (or a picogram of a nerve gas, probably!)

 

[sophiecentaur]

But nicotine isn't entering the bloodstream via your skin pores
Its entering via processes occurring primarily in the lungs

You may also consider that because blood plasma is >90% water
there are obviously processes occurring in the body that allow water to
enter and make up a large % of your blood stream


Dave

If you are "trying to give 'em up", you use skin patches.

 

[davenn]

true, like my pain killer morphine patches

Im assuming its an osmosis function occurring here ?

... wanders off to google to find out

Dave

 

[davenn]

OK from ...

http://www.transdermalspecialties.com/technology.html

Technology

The Transdermal Delivery Systems

Transdermal systems deliver drugs through the skin into the bloodstream. Medications delivered via skin patches avoid liver metabolism, a necessary feature for drug molecules to metabolize easily, and allows for lower dosing of medications. There are two types of transdermal delivery systems:
•Passive – In passive transdermal systems, the drug diffuses through the skin via the process of osmosis where it can act locally or penetrate the capillaries for systemic effect. This technology is only effective with small molecule drugs such as in nicotine patches i.e. nicotine has a molecular weight of 162 Daltons versus 5,808 for insulin.
•Active – In active transdermal systems, a physical force is used to facilitate the movement of drug molecules through the skin. By using an applied force (such as ultrasound), active transdermal systems are capable of delivering proteins and other large molecule formulations through the skin and into the blood stream at a speed unmatched by invasive systems such as micro needles and insulin pumps.


cheers
Dave

 

[Mintaka]

it's fascinating :-) You are saying that soap and water can actually get into my bloodstream when I'm having a bath...:-) It's a strange thought...))) I was led to believe the skin is like goretex, allows sweating out but no way in...))) You guys are brilliant, thank you...

 

[sophiecentaur]

Goretex works in either direction but the majority of the water will go from the more concentrated region to the less concentrated region (normal rules of diffusion). Larger molecules will probably not pass through goretex. Because the 'holes' in your skin are not just simple geometric shapes (there will be a pattern of charges around them) there will probably be a certain amount of selectivity which is more than just dependent on the physical size of the molecule trying to get in.
Edit: On the subject of goretex membrane, there were a number of goretex tents on sale about ten (?) years ago. They then ceased to appear in the shops. I asked a guy in an outdoor shop about that and he said they didn't work very well because "you need a difference in climate between inside and outside". I presume he meant a difference in temperature on the inner and outer surfaces - to raise the vapour pressure slightly on the outside. In a tent. the air next to the internal skin of the tent is likely to be cooler than in clothing - nearer the body.