you beat me to the punch with making this thread!
Aspirin is acetylsalicylic acid and is a derivative of salicylic acid which is a proven acne fighting ingredient. Aspirin doesn't become salicylic acid on the skin, but aspirin itself has similiar properties to salicylic acid. In relation to acne, aspirin is anti-inflammatory and antibacterial and also has exfoliating properties which help to clear and tighten pores.
I've been using the aspirin mask every couple of weeks or so but since I have a wedding I want to look good for next weekend, I 've been using it the past 4 days in a row. Besides some minor purging (which i hope is now over), my skin is looking much better - its smoother, red marks have reduced, and acne has healed much quicker. The mask seems to make me red after using it, but it goes away and leaves me with an overall better appearance after an hour or so. I'm hoping that it can keep me clear for the next week or so!