Mr Keyhole was a master of transformative magic. He can use advance spells without a wand or any other magical device and he can made them work instantly or progressively. His talent was so well-known that long time ago he was recruited as a professor at a famous male academy of magic. Unlike other professors, he continuously uses magic on his students so they can experience the consequences first hand.
That day, mr Keyhole was enjoying his Sunday at a small mall near the school. He wanted some time of peace and quietness before the next semester starts. New students are always hard to deal with, but he knew it worth to see them grow up into powerful magicians like him. Particularly, that year he would have a very young group, boys around 10 years old. A drastic change from the teenagers he was used to.
Mr Keyhole was minding his own business when he spotted a group of teenage girls pointing at him and giggling. He immediately realized they're making fun of him, maybe talking about his looks, his overweight, haircut, etc. He wasn't particularly handsome but he was clean and healthy, and those things were more important to him. He tried to ignore them, but they're getting quite annoying.
So, before they leave, he casted a little spell on them. For the next few days, they'll be suffering from a severe itchiness. It won't be permanent but that would take their whole attention meanwhile. They won't have time to make fun of anyone else. Mr Keyhole smiled, he added a little mischievous extra spell, so their itchiness would be stronger at night. "This is going to be a nice story for my new students." He said before he left the mall.