Prof Ariens said: "We did laboratory and animal studies which showed this film could be a barrier against microbial infection for at least 12 hours, and this gives the immune system time to get white blood cells to the wound to counteract any infection."
Adding petroleum jelly perforated the protective film.
Prof Ariens said: "If you get a scrape or a cut it is best to let it clot for half an hour to let the film form. Do clean it of course if it needs it, but the clot will make its own perfect plaster. After that, it might not be so bad to add petroleum jelly, but before then, from our findings, it appears to damage this film."
Independent wound care advisor Jacqui Fletcher, who is also the clinical editor of the journal Wound UK, said: "You do see it used in sports. Boxing is a good example. If the fighter gets a cut they can use it to stop the blood running down the their face so that they can continue the fight.