i have had ,mild acne prone skin for years on and off and can never seem to pin point why i suffer, i have also been usinf studio fix for about 2 years now....after my skin suffered a big flare up i decided i wanted to swap to a lighter foundation....while searching i saw the reviews of MAC SFF on here and *BINGO* noticed other people saying they had small bumps under their skin as well as breakouts from this foundation....I imediatlly stoped using the SFF and switched to Revlon colorstay ....I have seen a HUGE improvement in my skin since doing so...the small bumps that used to be under my skin have actually disappered and i have no new pimples or spots since...where as before i would get atleast one every other day!! I know this is a heavy foundation but i was always careful in making sure i removed it properly, i removed it with cleanser and then used a wash with my clarasonic mia so i know it was not the fact i didnt remove the make up throughly enough that caused the skin trouble....after doing research i have found out MAC foundations in contain many pore clogging or comedogenic ingredients...look on this website http://facerealityacneclinic.com/articles/pore_clogging.php if you are intrested in checking ingredients in other foundations.... I know everyones skin is different but i really do think this foundation has not helped me with my ficght against acne and i do know lots of people use it to cover up acne because of its good coverage, which could be making it worse (as in my case)...anyway sorry for blabbing on! if it hadnt have broke me out i LOVE the colour match and the range of shades and the yellow base which matches my skin when i tan it! althoughi did feel it very cloyy and heavy for a day look and also it used to slide off my t-zone after 8hours wear. also i dont know if i was imagining it but it used to make my skin itch sometimes! anyway hope that helps some one!