As a writer, I *always* like the magical stuff to have consequences, you know. For instance, slip somebody a love potion and you’ll never be 100% certain they really like you, or it was the love potion tricking ‘em. (*cough* *cough* HBP *cough* *cough*)
Another thing I created, a sensitizing ointment, good for treating sunburns, but also makes the skin super sensitive, so you can see the sexual use Medicinal grade will add a bit of stinging nettle to help thwart addiction. However, abuse it and it’ll trigger puberty (good if you need somebody to be capable of producing an heir...this week). Of course, being the author I am, I happily provided it to first years.