How do wounds heal when petroleum jelly is applied?

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.