Is it safe to put itching powder in a baby's diaper?

April Fool's Day is nearly here and I have some nasty itching powder ready for the ultimate April Fool's Day prank. A friend of mine and his wife, both finding my prank idea absolutely hilarious have given me permission to prank their daughter on April Fool's Day. She only recently turned two-years-old, has never been pranked before, and still has no concept or interest in the potty or toilet, so she still needs her diapers at all times and doesn't know how to take her diaper off. I plan to take full advantage of this because on April Fool's Day, I'm going to play the ultimate prank on her by putting the itching powder in her diaper.

I have never used itching powder, nor have I pranked a baby before. I did test a little bit of the itching powder on my arm and it is very itchy and did make that spot on my arm a bit irritated, but after wiping and rinsing my arm, the irritation and itching quickly went away. I do plan to put the rest in her diaper, and I know it is going to make her really itchy but I don't know how she is going to react, nor what other effect it could have on her.

What I am asking is should I go through with my ultimate April Fool's Day prank? Is it harmless? Is it safe to put itching powder in my friend's baby's diaper?