I've used this for about a week w/o problems. I've been using it as a base to apply before I use my edm matte ftd and concealer (in that order). I find that it does make my face quite matte and reduces the need for blotting thru out the day. it also essentially eliminates the need for a silicone based primer (smashbox photofinish) although i still use this on the t zone before the silk dust if i think i'll be out all day/night or will be esp. hot and sweaty.
the silk dust is essentially colorless, and provides no coverage, just a matte base to apply color. i have had no skin reactions thus far but will update if otherwise. so far i love it! i bought it part of the 12 item custom kit so it worked out to be <$5 each which is a great deal for the large amt you get. a light dusting is all you need!