Why do villagers think my healing spell is a fire spell?

I'll be walking around the towns and cities of Skyrim, when all of a sudden, I'm told my guards and passerby that I should take care with those flames. Except I don't actually have any fire casting spells equipped when this happens; all I have is healing. Is this a scripted dialogue that NPCs will say no matter what spell you have?

As pointed out by @Paul and @Armadillo, this was due to me dual wielding an Orcish Sword of Scorching in my right hand while casting a healing spell in my left. It wasn't the healing spell that triggered this response, rather, it was the sword (even though it ran out of the enchantment, it still triggers this same sort of response). See here for more information.