I don’t know about Vaseline but I use a very light coating of olive oil on the surfaces of my silicone molds that touch my ear canals and avoid putting anything on the surfaces that have the receiver and vent openings or the receiver wires. I would think if either the Vaseline or olive oil gets into your body, the olive oil is a lot more metabolizable (Mediterranean diet!). I put a small amount of olive oil in a thoroughly cleaned and dried brown dropper bottle that I bought fairly inexpensively on Amazon (couldn’t easily find similar in pharmacy sections of Walmart or supermarkert). I put a drop on a small plate, touch my fingertip to it. Next day, I put another drop on a slightly different spot on the plate, and keep going until the tea saucer-sized plate has drops all over it. Wipe them off with a Kleenex and wash the plate in the dishwasher and so on. I got the olive oil idea from reading other posts on the forum.
Aqueous creams are better, there’s always been the suggestion that petroleum based products can deteriorate certain types of plastic, acrylic or silicones.
My Audi gave me a little bottle of Comfort Ear. I put a very small drop on my finger and carefully apply it to my dome avoiding the receiver and the dome slides easily into my small canal. I think the bottle will last over a year with the small amount I use each day. It has stopped my itchy ear feeling.
“Something used on babies couldn’t possibly be carcinogenic?!” Consider Johnson & Johnson and all the talcum powder suits …
The Wikipedia article on Vaseline, a brand, says that it’s highly refined, triple-purified, and generally regarded as safe (but less rigorously prepared competitor brands might not be Petroleum Jelly May Not Be As Harmless As You Think | HuffPost Life)) and materials regarded as carcinogenic are removed in the purification of Vaseline from its petroleum base. Since it’s all Wikipedia or HuffPost, it’s hardly peer-reviewed scientific information, though. (and from the editorial comment at the end, there apparently was some pressure to update the HuffPost article to specifically mention that the Vaseline brand is generally regarded as safe - not in the original article).
I should imagine the risk is pretty low. I just wonder about what happens to anything we apply to our skin or other epithelial cells, including the fate of sunscreen, etc. Most of us are pretty old, too. So the older that you are, the less likely within your remaining lifetime that any faintly or possibly carcinogenic thing is going to have an effect. And the ultimate irony of living a long, long time and not dying of anything else is that eventually cancer from “natural” DNA mutations is going to get you, if nothing else does …