Is petroleum jelly-lip balm dangerous

No, as far as I know it is not dangerous. As a matter of fact, it can be used to remove eye make up and restore chapped lips.

For people who have to be on oxygen all the time, you should NOT use petroleum based lip balm or moisturizers. Also, if you have some kind of open sore or infection, the lip balm may just cover the bacteria and not allow topical medicines or air to get to your lip so it can heal. Petroleum jelly by itself doesn't have any medicinal properties, it only protects from more moisture or from drying out.