I have just read what has to be one of the funniest and hottest stories it has ever been my pleasure to come across.
The Vipertooth's Kiss by
eeyore9990. It's over on IJ, posted in Daily Deviant.
Charlie is injured, and enjoying the pain a bit too much. Snape gets a whiff of the Chinese Fireball "secretions" that are smeared on Charlie's skin. It's a bit... intoxicating, but Snape never loses his Snapishness, even if he can't stand up on his own.
Excerpt:
"Ah. A mating secretion laced with enough pheromones to drive a fully grown man insane with lust. Which is why the Chinese use it in their fertility potions. I've always found it rather unstable in most common bases and too expensive otherwise." Severus swayed and frowned when Charlie pushed himself off the table, strong arms coming around Severus to guide him gently into a nearby chair. "Did you know that, when mixed with guava berries, it can also cure erectile dysfunction?" Charlie's smile wavered in Severus' vision, causing him to blink to clear it.
Read and enjoy, but don't be drinking anything as this fic definitely needs a beverage warning!