[Daniel]

Daniel  asked the Naked Scientists:
   
Dear Naked Scientists,

I was wondering how wounds heal when a lot of petroleum jelly or neosporin is applied to the wound? What does the body do with the foreign material? Absorb it, grow through it? Just wondering if anyone knew.

Thank you all!

Daniel Spain
Nashville, Tennessee USA

What do you think?

[SteveFish]

I will make a try at this. The interior of the body is an aqueous environment and oily substances can't penetrate. This is sort of like putting oil (or petroleum jelly) on water where it will be excluded by the water, and because it is lighter it floats on the surface.

There are a lot of lipids in our bodies, but they are always kept separated by barriers. For example, cellular membranes contain a lot of fatty acids but membrane lipids have a hydrophilic (water loving) portion that orient toward both the outer and inner surfaces of the membrane and contain the hydrophobic lipid in the membrane interior separated from the watery extracellular and intracellular environment. Also, fats in the body are stored inside of fat cells (adipocytes) away from extracellular space. In an aqueous environment, unprotected lipids would stick together and form large clumps like the oil droplets coalesce after shaking oil and vinegar salad dressing.

If you were to inject oil or petroleum jelly under the skin, where it couldn't be forced out, it would remain as a large droplet or chunk that could cause problems. An example of where this happens is when someone working around hydraulic lines is exposed to a high pressure leak that drives the hydraulic oil under the skin. This is considered to be a serious injury.

EDIT-- I forgot to answer the question. A typical small wound heals from the bottom up and this, combined with the hydrophobic effect (explains separation of oil and water), would force the petroleum jelly out as it heals in the usual manner. The petroleum jelly, especially if it contains antibiotics, would serve to protect the wound from invasion by microorganisms, but I am pretty sure that unmedicated petroleum jelly wouldn't be as good as a scab.

[thedoc]

We discussed this question on our  show
We put this question to Dr Suzy Lishman:
Suzy -  Thanks, Daniel. It’s a good question. I think the first thing to say is the petroleum jelly itself has no medicinal effect and it doesn’t actually effect whether a blister forms, and it’s not absorbed. So, it doesn’t get absorbed into the wound. But its effectiveness in wound healing is related to its sealing effect on cuts and burns. So what it does, it stops germs getting into the wound so it doesn’t get infected so it can heal more quickly. It also keeps the area supple. It prevents the skin’s moisture from evaporating, so it stays nice and moist, and supple, and it enables that area to heal without cracking.
The really important thing about putting petroleum jelly on burns for example is, you must not put it on a fresh burn because burns continue to damage the surrounding skin for some time because the heat continues after the initial burn occurs. If you put Vaseline over the top of that, then it will actually trap the heat in and more damage will be done to the underlying skin. So it’s essential that you wait until the burn is completely cooled down before sealing it.
Chris -  The other interesting about the way wounds heal, that has been discovered fairly recently, is they actually create an electrical current into the wound. Researchers in Aberdeen started measuring this, they put a wire in the root of the wound and the wire on the edge of the wound, and they could measure an electrical voltage difference between the two, and the cells flowed down the potential difference. So they can sense the voltage and they move into the base of the wound from the margin of the wound where it’s healing up. And because they're blebbing off from the side, if you do put a layer of petroleum jelly over the top, they're just going to go underneath it. Aren’t they, Suzy?
Suzy -  Yes, they are. They're not bothered whether it’s there. It just gets in the way. They go around the edge of it. So, it doesn’t actually have much effect on the wound healing itself. It just enables it to happen.
Click to visit the show page for the podcast in which this question is answered. Alternatively, [chapter podcast=2823 track=10.11.01/Naked_Scientists_Show_10.10.31_7432.mp3] listen to the answer now[/chapter] or [download as MP3]

[JnA]

great post.. food for thought