Yeah, the antiperspirant thing is a problem for me as well. I had to totally stop using drugstore antiperspirants/deoderants for almost a year because they all irritated the crap out of my underarms. We're talkin' really painful itchy redness. Every single drugstore deoderant I've found has cyclopentasiloxane in it! :P I used a mineral salts spray to prevent odor and just had to go without the antiperspirant. That's find for winter but I do sweat a lot and it drives me nuts so I've been experimenting with antiperspirants again and I'm having some success with the aresol sprays. The have the 'cone and aluminum but the aluminum content is just over half the percentage of the solids and gels and the spray delivery seems to give me a much more tolerable amount of cyclopentasiloxane. So far I'm not clawing my skin off and avoiding half my wardrobe/bras (it was a rough period, lemme tell ya!) so I'm pretty happy. Let's hope it keeps up.
If anyone knows of an antiperspirant (not just deoderant) that does not contain cyclopentasiloxane, please please PLEASE let me know!!