Um. Hmmm. Toothpaste, eh? my mother used to use toothpaste on mosquito bites, i tried it but it didnt help. I can't say I've ever heard of it for acne, maybe if it had peroxide in it I could see the peroxide drying the acne out.
I'd try tea tree oil, it's a natural antiseptic/antifungal/topic antibiotic and not full of the crud that is in your typical toothpaste. Commercial toothpaste has some really nasty stuff in it.
meg