https://en.wikipedia.org/wiki/Robert_ChesebroughVaseline was a by product.
"Chesebrough began his career as a chemist clarifying
kerosene from the oil of
sperm whales. The discovery of
petroleum in
Titusville, Pennsylvania, rendered his job obsolete, so he traveled to Titusville to research what new materials might be created from the new fuel. As he was strolling around the oil field, he found out about something called rod wax, also known as
petroleum jelly, a jellylike substance that was cleaned off of the pumping equipment often. Chesebrough was told it was a nuisance, except when someone had a cut or burn. If it was rubbed on an injury, then it would lessen the pain and make the injury heal quicker. He then trade-named the jelly as
Vaseline. "
"Chesebrough's success stemmed from a firm belief in his product. Before he began selling petroleum jelly, he tested it on his own cuts and burns. Chesebrough was still unable to sell any to drug stores until he traveled around New York demonstrating his miracle product. In front of an audience, he would burn his skin with acid or an open flame, then spread the clear jelly on his injuries while demonstrating past injuries, healed, he claimed, by his miracle product.
[4] In reality, it doesn't heal cuts and burns, the jelly forms a layer, causing dirt to not get in (one of the leading causes of death and disease in his day were due to open wounds being infected) and trapping the moisture in. To further create demand, he gave out
free samples, one of the first instances of it ever being done."