Dont listen to this. They dont know what theyre talking about. Not every steroid is the same, so just because a steroid they used didnt work, doesnt mean this cant. And just because it didnt work for them doesnt mean it wont work for your son. I would listen to your doctor for now.
And I seriously doubt that Vaseline caused this for anyone and I really cant believe people are still insisting it did. People just start using Vaseline right after the beginning stages of EC or just happen to be using it for their dry lips before EC even starts, and then blame it on that. Most people on here had chapped lips before EC so everyone was using moisturizers. That doesnt mean they cause it. The EC would have come anyways.
The only way Vaseline or any other product could have caused this is if your allergic and after a few weeks of stopping the product this would have gone away. And if your worried about that get a patch test. But if you thought Vaseline caused this then that should have been the first thing you did.